The core or pith of plant stems are typically either hollow or contain loosely packed, spongy parenchyma cells. The pith of this butternut or white walnut (Juglans cinerea) is distinctive in that it is chambered with dark bands of sclerenchyma plates separating hollow zones. Black walnut (Juglans nigra), a close relative, also has chambered pith and has bands that are typically a bit lighter in color. Parenchyma cells are relatively large, of variable shape, and have thin cell walls. As developing stems elongate, parenchyma can tear and disintegrate in many plant species. Another cell type found in plants is sclerenchyma. Sclerenchyma cells help provide support to plant tissue and have thickened, secondary cell walls containing cellulose and are often impregnated with lignin. As stems of white and black walnuts grow, parenchyma cells eventually collapse leaving mainly sclerenchyma cells in distinctive plates.
Earlier this month, on April 7, Wisconsin reported a confirmed infestation of emerald ash borers (EAB) in the town of Victory. This town is in Vernon county, about 20 miles south of La Crosse and on the banks of the Mississippi River about one mile from the Minnesota-Iowa border. This the first time that EAB has been found in western Wisconsin.
The Minnesota Dept. of Agriculture has stepped up their surveillance efforts in Houston county which is right across the river from this infestation in Wisconsin. So far, their surveys have not revealed any EAB. Remember, that at this time, EAB has not been found in Minnesota (although the odds of finding it in Minnesota soon have gone dramatically up). Because of the imminent danger of EAB, a quarantine has been put in place for Houston county, restricting the movement of ash trees, ash logs and branches, uncomposted wood chips, and any hardwood firewood.
Minnesotans should be greatly concerned about EAB. Minnesota has one of the largest concentrations of ash in the U.S. with about 900 million found in our forests and urban landscapes. This insect is such a severe pest as it attacks all species of ash, regardless of size or state of health, killing them after three to four years of tunneling under the bark.
What can you do to help? First and foremost don’t move firewood from outside of Minnesota into the state. In fact don’t even move firewood within Minnesota. If you are going camping or any activity that involves firewood, buy it locally from an approved vendor, don’t bring firewood from home. And when you return home, don’t bring extra firewood back with you.
This is so important because firewood is the primary method EAB has for being moved long distances. By itself it only flies about ½ mile a year. But with peoples’ help it can travel hundreds of miles at a time.
People can also help by being aware of what emerald ash borer looks like and the symptoms of an EAB infested ash tree. An emerald ash borer is a slender, ½ inch long, iridescent green beetle. It is active anytime from late May into August. There are other insects (http://www.extension.umn.edu/distribution/horticulture/components/M1242-9.pdf) in Minnesota that are also green so look closely.
Be alert to trees that are suddenly showing signs of thinning foliage and dead limbs. An emerald ash borer infested tree will show signs of D-shaped exit holes (although they may not always be easy to see). If you were able to look under the bark, you would find a series of S-shaped tunnels backed with frass (sawdust and insect droppings). Although there are other problems that can cause to ash to dieback (http://www.extension.umn.edu/gardeninfo/diagnostics/deciduous/ash/index.html), it should be a red flag that should cause one to look more closely. Use the ‘Do I Have Emerald Ash Borer’ diagnostic web page (http://www.mda.state.mn.us/news/publications/pestsplants/pestmanagement/eab_doihaveit.pdf) on the Minnesota Dept. of Agriculture web site for help in deciding whether you have EAB.
For more information on emerald ash borer see, http://www.extension.umn.edu/distribution/horticulture/M1242.html
Apples in the Home Garden
If you’ve ever dreamed about harvesting fresh fruit from your garden, apples are a great option. Sure, they require a bit more care than a typical landscape tree, but with a little TLC you could be harvesting juicy, crisp apples right from your own backyard!
There are a few things to keep in mind when growing apples that will help you achieve bountiful harvests of high quality fruit year after year. First it is important to know that apples require cross-pollination to reliably set fruit. This means planting more than one kind of apple tree. Your choice of varieties will largely depend on your priorities. If one tree will give you all the fruit you need you may want to consider planting a disease resistant flowering crab apple, such as Indian Summer or Snowdrift, for cross-pollination. Crabapples and edible apples can successfully cross pollinate. These trees are used in commercial orchards because they bloom over a longer period of time than most eating varieties, ensuring complete overlap of bloom. This equates to greater pollination potential of all the flowers, leading to more fruit. (Ensuring complete pollination and greatest fruit set might not be necessary however, which will be covered later when we talk about thinning.) These crabapple varieties and many others produce a profusion of flowers in the spring, and will then set an abundance of pretty, though inedible pea- to cherry-sized fruit which will dangle on the trees through the winter and into the next spring. Since the tissue of the apple fruit that we eat is derived from cells of the maternal parent tree, the apple that serves as the pollinator will not affect our fruit quality.
If you’re interested in more fruit to eat, you may want to choose another eating variety for cross-pollinatio. Zestar!, Snowsweet, and Honeycrisp apples are highly recommended for home gardens. These popular University of Minnesota varieties offer home growers a variety of flavors and harvest times. Planting an early-season variety such as Zestar! with Snowsweet – a late-season apple – means a full season of fresh fruit. The University of Minnesota hosts several websites that may be helpful as you choose varieties and plan your planting.
Do you have a couple of apple trees in your yard that just aren’t producing much fruit? Do you get a lot of apples each year, but they’re smaller than you would expect? Thankfully there are some simple things you can do to improve yields and increase fruit size. Before that though, it is good to remember that apple trees take about 5 years to reach maturity. This means until then they might produce little or no fruit. So when it comes to apples, patience is definitely a virtue.
There are a few things to understand about the behavior of an apple tree. An apple tree’s primary goal each season is to produce seeds…as many seeds as possible. It starts this process by producing flowers, lots and lots of flowers. Once these flowers are pollinated and set fruit, the tree will naturally put much of its energy into developing that fruit. That seems great, right? Well, not exactly. What we can’t see is that shortly after fruit set, flowers are actually forming for next year inside buds. The tree will ignore these flowers, putting everything it has into developing a lot of the current fruit filled with seeds. This is why most apple trees, when left to their own devices, only produce a large amount of fruit every other year. In other words, they are naturally biennial. We can change that to a large extent through fruit thinning. Thinning involves removing excess fruit to allow space for remaining fruit to grow large, and to allow flower initiation and development for the following year. Thinning also promotes improved fruit uniformity, color, flavor, and reduces limb stress and breakage.
So when is the best time to thin? This is the tricky part. There is a short window during which you should thin an apple tree, which falls between fruit set and flower initiation. Fruit set occurs after the petals have fallen off, and the remaining ovary begins to swell. That’s pretty simple. But if we can’t see the flowers, how do we know when initiation happens? Thankfully flower initiation is dictated by day length, which is quite reliable, and generally occurs around June 20 in this region. Fruit thinning should be done before then or next year’s harvest will be compromised. A good rule of thumb is to thin the tree when the fruits are about ½” in diameter, or about the size of a dime.
Most apple trees will self-regulate to a small degree, meaning they will drop some fruit to reduce the burden. This is called the June drop period, and in this time the tree will naturally abscise some of the tiny fruit. Abscised fruit is recognized by a yellow pedicel – the stem that connects the fruit to the tree. These fruits become loosely attached and can be removed with a flick of the finger. June drop may happen before or after the ideal thinning window, so don’t rely on it as a guide. Just remember the ½” rule.
How much should we thin? If you look closely, you’ll see that each bud produces a cluster of about 5 flowers. The first and largest flower in each cluster is called the ‘king bloom’ and it will go on to produce the ‘king fruit’, the largest fruit in the cluster. Ideally, this is the one to keep, but it can sometimes be difficult to determine when the fruits are so small. Generally, fruit should be thinned to a spacing of about 6”. This may seem excessive when looking at those tiny apples, but consider when they grow to 3” or so how close together they’ll really be. And that is when they’ll need a lot of light to mature, and will be weighing down the branches. A spacing of 6” will allow the tree to produce large, uniform fruit while conserving some energy to work on flower buds for next year.
So how exactly do we thin the fruit? Thin by carefully plucking the tiny fruits off the ends of their pedicels (stems). This prevents any injury to the spur which is holding next year’s buds. You can use a thinning shears to make this a little easier. Just snip the fruit off right at the top.
One note of caution: Haralson apples are very prone to biennial fruiting. If you have a Haralson tree and you want it to produce fruit every year, you may have to thin so excessively that you get only a small crop. In this case it may be best to permit its biennial nature and get a large crop every other year.
Pruning and Training
Pruning is essential to reliable fruit production on apple trees. Again, left to its natural course an apple tree will send out branches every which way and will fill them with fruit, resulting in small apples, uneven development, and overall reduced productivity. Proper pruning spaces out the fruit, allows more sunlight to reach the fruit, increases airflow in the canopy (which reduces disease potential), and focuses the tree’s energy into bigger and better-tasting apples. Pruning is the key to productivity, and if done consistently every year is a rather simple and enjoyable task. Understanding a little about tree growth and following a few simple guidelines will give you the confidence to prune without fear!
Before we get into pruning, we should first talk a little about training. Training is done primarily when the tree is young, and starts right after planting. Think about training a puppy. You want to develop good habits right from the start, because trying to go back later to change bad behavior will be far more difficult. It is similar with apple trees. Proper training will help to establish a well-structured tree that will be easier to prune and maintain in the future. Attempting to straighten a leaning trunk or reposition branches that are several years old will often prove difficult.
A common training system for apple trees is the central leader system. The goal of this system is to create a strong, vertical central stem, or leader, off of which grow strong, evenly-spaced side branches. The result of this training system is a well-proportioned tree which is narrow at the top and wide at the bottom, similar to the shape of a Christmas tree. The open, evenly spaced braches allow for good light penetration and air circulation, both of which promote fruit production and lower the risk of many diseases. Training is accomplished by tying the main stem to a sturdy, vertical support and then pressing young side branches to an angle of about 45° to 60° from the stem. Branches at this position will produce a balanced amount of vegetation and fruit. This training is done using things like clothespins, rubber bands, wooden spreaders, ties, and weights. Young, supple branches that are 3-6 inches long can be easily positioned in June. Older branches can be positioned any time between late winter and early summer. An excellent publication from the University of Wisconsin offers detailed explanations and diagrams of how to properly train a tree to the central leader system. This publication can be found at http://learningstore.uwex.edu/pdf/A1959.pdf.
During the training phase – the first 3 or 4 years – careful pruning allows you to select the branches that will create the structure and foundation of the tree, which will determine its form from here on out. The strongest branches are the ones to keep, and should be evenly spaced and staggered so they are not directly above or across from one another.
As the tree matures, pruning is done to maintain the shape of the tree and encourage fruit production. If the tree has been well-trained it will require little pruning, but should definitely be pruned every year. For this kind of maintenance pruning, here are some tips to follow:
Finally, pruning is done when the tree is dormant, in late winter or early spring when risk of severe cold damage is past. March and April are the best months to prune. If you wait until growth begins, the risk of infection and disease is much greater. Prune early and don’t be afraid to prune a lot. Your tree will thank you.
The following websites offer detailed training and pruning recommendations:
A Word about Fertilizing
A soil test every two or three years will provide accurate recommendations for what type and at what rate you will need to fertilize your apple trees. The University of Minnesota can conduct a soil test for you. The most important time to test your soil is before planting, because this is when it is easiest to amend your soil with lime, phosphorus and potassium if they are needed. These amendments are most effective when incorporated in the soil. Once the tree is planted, incorporation is difficult. The U of M soil testing lab website (http://soiltest.cfans.umn.edu/) offers guidelines on how to submit samples for testing, and how to read and interpret the results. Follow the fertilization requirements on the test and you will maintain healthy, productive trees. Avoid over fertilization with nitrogen, which is especially important with apple trees. Over-fertilizing with nitrogen will cause excessive vegetative growth at the expense of fruit production.
It is best to apply fertilizer in early spring after the ground has thawed. Spread a wide band of fertilizer around the tree’s drip line – the outline of the widest extent of the branches – and about 4 inches beyond. Keep fertilizer at least 6 inches from the trunk, as the fertilizer may burn the tree. Detailed advice on fertilizing apple trees can be found athttp://www.extension.umn.edu/distribution/horticulture/components/1731-9-soiltest.pdf (scroll down to page 33).
A Garden of Plenty
Growing apples in the home garden is a wonderful way to bring fresh, delicious fruit to your family with the satisfaction of having grown it yourself! It’s also a great opportunity to teach children about where fruit comes from, about fruit trees and tree care, and about the fulfillment that comes from growing your own food. With a bit of patience and a little effort your trees should offer abundant harvests year after year.
“Just opening the gate and stepping into the garden filled me with peace. My little plot looked like a bush and I brought my granddaughter [the see it] and she just felt everything with her hand.”—Sabathani gardener
They aren’t visible from the street, but just north of Minneapolis’ Sabathani Community Center, members of the Urban Gardener program are already busy working on plots that will soon be bursting with vegetables. Launched in 2007 with a grant written by Extension Urban Director Barbara Grossman, the program is about much more than gardening. It also aims to build community, help families stretch their dollars a bit further by growing some of their own food and offer information about nutrition and healthy eating.
Hennepin County master gardener Mollie Dean, who has been coordinating the program since its inception two years ago, says interest has grown quickly with over 275 people attending gardening classes so far and more than 55 people crowding into the program’s first class this April. Most participants are first-time gardeners and many of them live in the surrounding neighborhoods. “We’re seeing a lot of young couples this year, but we also have a lot of parents and children, as well as grandparents and grandchildren,” she says.
To help participants gain the skills they need to be successful gardeners, the program is based on a six-class curriculum (which is currently in the process of being replicated for use by other counties statewide), including lessons on soil, planning a garden, design, selecting plants and maintenance. Those who complete all six classes are declared Certified Urban Gardeners and awarded a certificate, which is presented during a graduation ceremony held in mid May each year (this year it will be May 16th). Last year’s graduation drew a large crowd of proud family members and neighbors, Dean says.
About 25 master gardeners are currently involved with the program (more are definitely needed) and they work with people on everything from planning how big a garden will need to be to feed their family to actually sketching out a design plan on graph paper. Because gardeners come from a variety of ethnic backgrounds, the master gardeners who volunteer with the program spend time working with people to ensure they are able to grow things that suit their needs. Master gardeners also maintain their own demonstration plot, which helps them in explaining a lot of the ins and outs of vegetable growing. The plot is staffed every Saturday in June, so interested gardeners can stop by and ask questions.
Within Sabathani’s established community garden, which includes fifteen 40 ft. x 40 ft. plots, the Urban Gardener program has two 40 ft. x 40 ft. squares, which are divided into 10 ft. x 10 ft. or 10 ft. x 20 ft. plots. “We try to get people to choose the smaller size their first year because we want them to succeed,” Dean explains, adding that it’s often hard for participants to carve out the amount of time it takes to maintain a plot all summer. Twelve people worked plots in the community garden last year while other gardeners in the program chose to use their skills in their own backyards, or in other community gardens. One older woman, who took the Urban Gardener classes and enjoys taking care of container plants, brought her five adult children along last year because she wanted them to learn how to garden, too. This year, Dean expects to have about 25 people tending plots in the garden. Terry Straub, program coordinator for the Hennepin County master gardener program, hopes Sabathani gardeners may also consider becoming master gardeners in the future.
While some people do plant a few of their own flowers, the program supplies everyone with vegetables at no cost. The bulk of plants come from donated seeds. But master gardener Joan Onffroy has also helped out by starting over 200 seedlings for participants for the past two years. To encourage a sense of community, everyone is asked to help each other throughout the season. During the program’s fall harvest festival, all of the plots are cleaned up and everyone sits down to a big potluck meal, which includes plenty of dishes made with produce participants have grown. “People are so proud of what they accomplish,” says Dean. “And right now, with everyone being so interested in locally grown food, this really seems like the right program at the right time.”
Taking plants from the relatively low light and moderated temperatures of the home environment and plunging them suddenly outdoors in bright sunlight, wind, and temperature extremes can result in severe injury. Depending on the extent of the injury the plant may be capable of recovering relatively quickly, after multiple weeks, or in extreme cases not at all. As plants grew indoors, the tissues that they produced were adapted to those environmental conditions. With a gentle transition period, plant tissue can adapt to some degree when conditions change.
Plants use environmental cues to help them adapt their tissues to their current growing conditions. For instance, leaves produced in shade typically have more surface area and are thinner in order to better intercept light and best invest energy resources into the most efficient type of tissue. Leaves grown under brighter light are often thicker with additional layers of photosynthetic cells within them and have a more developed waxy cuticle layer in order to better conserve moisture. Higher light levels are often associated with greater heat and therefore a greater potential for water loss. Leaves grown under higher light conditions also are typically higher in pigments like carotenoids and anthocyanins that serve in part to defend leaves from damage from excessive light, especially UV light.
When tissue adapted to one environment is suddenly transitioned to a vastly different environment, it can suffer injury. For instance, when we take houseplants indoors in fall where they experience lower light, leaves produced under the higher outdoor light levels often cannot suddenly adapt to lower light and have a tendency to fall off. In the spring we are generally forcing plants to endure the opposite transition by taking them from lower light into higher light levels. If the transition to higher light is too fast, the tissue can suddenly become scorched. Scorched tissue has a silvery white cast and is often irreparably damaged. It can remain silvery-white or soon may transition to brown and die. The chlorophyll, which causes plants to be green, can be damaged so severely by sudden high light (along with the cells housing this life sustaining pigment) that they no longer can undergo photosynthesis. Such plants will hopefully produce new foliage adapted to the new light conditions and recover.
In addition to severe and sudden changes in light levels, sudden changes in air movement, water availability, and temperature also can significantly shock plants. Plants in small containers can quickly dry out outside and wilt on a warm spring day and a dry wind can speed water loss. Wind can also whip young plants and result in bruised and broken tissue. Temperature extremes can also stress and stunt plants, especially low temperatures for warm season species. Many tropical species especially can experience chilling injury at temperatures below 50F. The lipids or fats in their cell walls are typically more saturated than those of temperate species. Lipids with greater saturation transition from a liquid to solid phase at warmer temperatures (like margarine, a relatively saturated fat, is a solid at room temperature, while corn oil, a less saturated fat, is a liquid). Solidification of lipids within plant membranes compromises their ability to function and can result in severe and in some cases irreparable damage. Because of this, it is not recommended to place warm season crops like tomatoes and squash out too early as cold temperatures can dramatically stunt their growth. Often later plantings of such crops can outgrow earlier planted, cold stunted plants of the same species, thus negating the benefit of trying to get a jump start on the growing season.
Fortunately, a gradual transition from indoor to outdoor conditions can allow changes to occur in existing plant tissue to allow it to better adapt to the new environmental conditions and then start producing new tissue more fully adapted to the new environment. Often a gentle hardening off/transition period of one to two weeks is sufficient to allow existing tissue to adapt to the extent possible. Here are some tips to harden off your bedding plants and houseplants you want to transition outdoors:
Plants we purchase from the garden center are often grown in greenhouses with relatively high light and good air movement and the transition from that environment to our garden is less severe than from our home. Even so, sometimes a hardening off period can be beneficial, especially if we can tell that the plant was struggling for some time in the retail environment from perhaps being stored temporarily under a bench or in another less than ideal environment. Helping plants gently transition to their summer home will pay off in quicker adaptation and resumed growth.
Throughout Minnesota, purplish brown to rusty brown needles can be seen on spruce trees. A variety of problems can result in needle discoloration in spruces including insects, disease, and problems associated with environmental conditions. This time of year two common problems are Rhizosphaera needle cast and winter injury. Rhizosphaera needle cast is caused by a fungal pathogen. Winter injury is the result of environmental conditions. It is important to be able to distinguish between these two problems, since very different action is required to maintain tree health depending on the cause of the problem.
Rhizosphaera needle cast is caused by the fungi Rhizosphaera kalkhoffii and is most commonly seen on Colorado blue spruce, which are highly susceptible to the disease. White spruce and Norway spruce have greater resistance to the disease but can become infected when stressed. With the drought conditions present in Minnesota the last few summers, Rhizosphaera needle cast is showing up in a wide variety of spruce trees.
Trees suffering from Rhizosphaera needle cast can be recognized by browning of the older needles. The older needles are located at the base of the branch closest to the trunk, while the new needles grow from the tip of the branch. Diseased spruce trees often have branches with green needles at the tip of the branch and brown needles towards the base. In addition, the branches closest to the ground tend to be more severely infected, because humidity is highest there. Later in the summer the discolored needles will fall off. If a spruce tree has been suffering from Rhizosphaera needle cast for several years, it may appear sparse and have dead branches at its base.
The fungal pathogen of Rhizosphaera needle cast can be seen on infected spruce needles. Use a hand lens to closely examine discolored needles. Tiny black pimple like spore producing structures can be seen arising from the stomates, or air holes in the needle.
Spruce trees suffering from winter injury often have needle discoloration on the needles at the tips of the branches. Frequently this damage occurs on the south or west side of the tree due to excess wind and sun on those sides. In some cases winter injury is observed on trees receiving reflective light from a nearby building or car. The discolored needles often appear bleached or faded, with the tip of the needle most severely discolored. Winter injury can occur under several conditions. Needles can be killed by cold temperatures, desiccated by the wind, or bleached by the sun. If a spruce tree did not have time to harden off properly in the fall or is not fully adapted to Minnesota’s winters, complete browning of all needles may be observed.
If the problem is clearly winter injury, not much can be done for the tree at this point. Luckily winter injury rarely kills the buds of the tree and as weather warms, new growth resumes improving the overall color of the tree. Make a note to water trees throughout the summer to prevent drought stress and help the tree harden off next fall. In very exposed areas, spruces can be protected from future winter injury with a simple burlap barrier to block the wind and sun. Read ‘Protecting trees and shrubs from winter damage’ (http://www.extension.umn.edu/distribution/horticulture/DG1411.html ) to learn more.
If the problem is clearly Rhizosphaera needle cast, management strategies should be implemented to protect this year’s needles from infection. When new needles are half the length of mature needles, spray the tree with a fungicide whose active ingredient is Chlorthalonil. Completely read the label and follow all instructions when using a fungicide. Apply the fungicide once more at the interval recommended on the fungicide label (typically 3-4 weeks later). These two sprays will protect the needles from infection.
In addition several cultural practices will help to reduce the risk of future problems with Rhizosphaera needle cast. When planting new spruce trees choose Norway spruce or white spruce instead of Colorado blue spruce because they are more resistant to the disease. Concolor fir (Abies concolor) is another alternative to Colorado blue spruce and has relatively large, blue-green needles. Reduce moisture on spruce needles by controlling weeds around the base of the tree and redirecting lawn sprinklers to avoid wetting the needles. Reduce stress on spruce trees by mulching the soil around the tree and providing trees with water during periods of drought. Avoid planting new spruce trees near old infected spruce trees.
If unsure what is causing needle discoloration in the spruce tree, send a sample to the UMN Plant Disease Clinic (http://pdc.umn.edu) before implementing any management strategies.
Early May usually finds most Minnesota lawns well into turning green and in need of a first mowing. Remember that the early part of the grass growing season, late March through the first part of May, is when our lawn grasses produce the best root growth of the year. Therefore it is important to not be mowing too short as shorter mowing heights reduce the amount and depth of those roots. Maintaining an average mowing height for around 2.5 to 3.0 inches, even at this time of year, is appropriate. Those larger, more robust root systems are important in providing the plant with the necessary water and nutrients to sustain the plant through flowering and increase the plants ability to withstand summer stresses.
For average home lawns consisting primarily of Kentucky bluegrass and growing in sunny conditions, early May is a good time to apply that first application of fertilizer. Usually this will coincide with about the time you plan to mow for the first time. This will be especially true if there was no fertilizing done the previous fall. As a rule of thumb, the amount of fertilizer put down should provide about one pound of actual nitrogen (N) per 1000 ft2 of lawn area. It’s best to apply about ¼ to ½ inch of water following the fertilizer application to help it dissolve and move into the soil where it will be less apt to runoff and be available for plant roots to take up.
Early May is usually when we see peak dandelion bloom. This often causes people to run out and buy some form of a weed control product to kill them off. However, the real preferred time to kill dandelions is in the fall of the year when the plant is moving food down to the root system to be stored over winter. Nonetheless, there are many available products to kill dandelions even in the very active growth of spring. Be sure to choose a product that is labeled for dandelion control in lawns. Do not use products that are designed to kill all vegetation as they will kill the lawns grasses as well as the dandelions.
Weed and feed products designed to apply fertilizer as well as put down a broadleaf weed control product can be effective. However, where there are only a few scattered broadleaf weeds such as dandelions in the lawn you will be applying a lot more product to the lawn than is necessary or effective. You must get the product onto the dandelion foliage as these products do nothing to prevent new dandelions from emerging that start from seed. Thus, if there are only a few scattered dandelions in the lawn, using a pre-mixed, ready-to-use product to spray onto the dandelion foliage is much more efficient and effective. This strategy also introduces far less herbicide into the environment thereby reducing potential pollution and exposure problems.
As soil temperatures begin to warm in the early part of May, we approach the time when crabgrass control products need to be put down. Unlike the broadleaf herbicides mentioned above, these products must be applied before the crabgrass seeds begin to germinate. As the seedling root and sprout emerge from the seed, it comes into contact with the preemergent herbicide and is killed. Frequently this type of herbicide is packaged as a weed and feed product. The fertilizer provides nutrients to help thicken up the lawn grasses, which in itself works to reduce the amount of crabgrass seeds that will germinate and grow. It is a good practice to water in these products with ¼ to ½ inch of water (or rainfall) as soon after application as possible, especially with liquid formulations. This moves the herbicide down to the soil surface where it is bound tightly to the soil particles and provides the desired weed control effect.
A relatively recent addition to our crabgrass control options is a product known as corn gluten meal. It is a by-product of the corn processing industry and acts like an organic weed-and-feed product. It contains about 9 to 10 percent nitrogen and its preemergent weed control properties were identified and documented through research conducted at Iowa State University. The recommended practice for using this product is to apply it at 20 pounds of product per 1000 square feet of lawn in early May and again early to mid-August. Like the above conventional preemergent products it should also be watered in as soon after application as possible. This product works best when the crabgrass seeds begin to germinate, they contact the corn gluten meal (which in turn damages the newly emerging root) and this followed by a slight drought stress. The inability of the damaged seedling root to supply water to the germinating seed causes it to die. Control usually improves after the first year as the number of seeds available to germinate is reduced plus the added benefits of the nitrogen to improve the turfgrass stand also begin to take effect.
While it may not seem like early spring is a time when we should think about watering our lawns, there are times when it is beneficial for our grass plants. When conditions are warm, windy and dry, both our soils and grass plants can dry out to the point where they can experience varying levels of drought stress. Since spring is a very active period of growth, the less stress encountered the greater the ability of grass to tolerate typical hot dry conditions during the summer months. At those times in early spring when we experience warm, dry conditions, applying about an inch of water to the lawn will be beneficial. If temperatures remain warm to even hot and there is no rainfall, then staying with about an inch of water every 7 to 10 days will help reduce plant stress and keep plants growing actively.
Water is the essence of life. All living beings on earth depend on water for survival. Water is also a source of joy and beauty. Here in Minnesota with our 10,000 lakes, the headwaters of the mighty Mississippi, and the beauty of Lake Superior and the rivers that cascade into it, it is easy to celebrate the beauty of water. It is also far too easy to ignore how wide-reaching our impact on water resources is. From agricultural and industrial uses that benefit everyone to our individual use of water in our daily lives, we all consume and pollute water. All of us – individuals, communities, and agricultural and industrial enterprises – need to act with wisdom and stewardship to manage and conserve our water resources, ensuring that safe water will be available as a source of delight and health today and in the future.
These are the themes of Waterosity, the 2009 summer exhibition at the Minnesota Landscape Arboretum. Waterosity explores and celebrates the beauty and the complex interdependence of people, plants, and water by presenting interactive displays and activities about the joy of water and our need to be wise advocates of our precious water resources. The exhibit runs from June 6 through October 4 and brings together the voices of artists, scientists, and horticulturists to explore the interplay of people, plants, and water.
There are many facets of Waterosity for visitors to choose from:
Water-Wise Living Exhibition
Two Water-Wise Living demonstrations, The Cutting Edge on Lawns and Harvest Your Rain will show how people can use and manage water in environmentally responsible ways in their yards and gardens.
We can all be part of conserving water as we care for our lawns and gardens. The Cutting Edge on Lawns exhibit will be placed on the island in front of the Oswald Visitor Center and will demonstrate ways to conserve water. Stroll into the Gardener’s Idea Shed to see interactive displays on wise watering and gardening practices and products that both save water and promote plant health.
Surrounding the Idea Shed are demonstration plots of new water-efficient grass varieties currently on the market as well as future lawn grasses being developed by University of Minnesota turf research scientists. Additional plots are planted with a no-mow mix and an ecology lawn mix.
As property owners, we also have an important role to play in improving water quality by managing the water that lands on us, which is what the new permanent Harvest Your Rain exhibit will illustrate. When it rains or snows in urban areas, storm water washes over streets, roofs, paved areas and other hard surfaces, moving large volumes of water, sediment and pollution to sewers and adjoining water bodies. This pollution that runs off into waterways is called non-point pollution and includes litter, household hazardous products, motor oil, car washing detergents, fertilizers, pet and animal waste, boat discharges, septic systems, pesticides, eroding soil, and leaves left on streets and driveways (EPA, 2008).
As homeowners, we may feel that our contribution to managing runoff and water quality is insignificant. But remember that every residential property is part of a larger community and of a watershed, and that the combined effect of many property owners taking steps to manage their storm water will have significant results. The Water-Wise exhibit called Harvest Your Rain involves retrofitting three existing picnic shelters to show property owners different ways that they can manage storm water runoff from their roofs and paved surfaces.
One picnic shelter will show how to link a home’s gutter system to a set of rain barrels. A rain barrel is a simple, inexpensive and time-honored way to start managing your storm water. Water collected by a rain barrel or a set of linked rain barrels can be used to water plants, fill birdbaths, or for any other outdoor use. (Dittmann, 2008)
Rain gardens will be constructed around a second picnic shelter. Rain gardens are shallow depressions filled with shrubs, ornamental grasses, and flowering perennials that thrive in changing water levels. When sited and constructed properly, rain gardens are attractive plantings that capture and accumulate water from rooftops and other impermeable surfaces surrounding your home or garage. After a rainfall, water is detained in the rain garden for 24 hours or less until it infiltrates or evaporates. The plants in the rain garden help to infiltrate the water and trap pollutants. (Dittmann, 2008)
A green roof will be installed on a third picnic shelter to demonstrate how an impermeable roof that sheds rainfall can be replaced with a living carpet of plants capable of absorbing significant amounts of rainfall. The benefits of green roofs to buildings and communities are significant beyond storm water management; they reduce energy costs, improve air quality, mitigate heat island effects, and provide green space in urban areas. (MN Green Roofs Council, 2007)
Other Waterosity-related Features at the Arboretum
The existing parking lot rain gardens provide a working model of how to handle rainwater runoff in a large-scale parking area, featuring swales and plantings able to tolerate drought and short-term flooding.
The five bays of the Marion Andrus Learning Center parking lot demonstrate the differences between impermeable and permeable paving and how these differences in combination with different landscaping styles affect the amount of runoff generated during rainfall. Porous pavements reduce runoff by allowing storm water to pass through surfaces that would otherwise be non-permeable. These new materials are modifications of traditional concrete, blacktop or interlocking concrete pavers that present a solid surface for pedestrian and vehicular traffic while allowing water to move into through the surface and base material. (Dittmann, 2008)
Ten years ago the Spring Peeper Wetland Restoration program started. A field has been restored to a sedge meadow wetland similar to the plant community on the site originally. Visitors can stroll on the boardwalk through Spring Peeper Meadow and enjoy the plants, birds, insects, and frogs that once again call this wetland home.
Go Green With a Splash Juried Exhibition
Ten designs submitted by artists, scientists, horticulturists, landscape designers, architects, and environmental organizations and chosen through a juried competition process will be installed outdoors in Arboretum gardens and natural areas, especially in and around water features. Some of these designs explore a ‘Plants & Water’ theme by focusing on the essential nature and movement of water in plants. Other designs explore a ‘Green & Blue in the Ecosystem’ theme with exhibits about invasive plants in wetlands, interactions between plants and animals that live in watery places, the role of wetlands in flood prevention and groundwater filtration, or the use of living willow-woven walls for erosion control. Designs focused on a third theme, ‘Pools of Reflection’, explore the impact of humans on our water resources.
Waterosity Family and Children’s Activities
The Water Works Plant Lab will be available for kids and their families on Saturdays and Sundays this summer at the Marion Andrus Learning Center. Here children will learn more about water, plants, and making good choices through hands-on activities and through teacher-directed formal programming. Children can peer inside of a plant’s “plumbing” to see where water goes after being taken up by a plant, meet plants that live on or under water, and explore the interaction of water and individual plant parts.
The Blue & Green Express is a kid-friendly version of the arboretum’s tram ride that will be offered on Thursday evenings this summer. The express will be led by family program staff and will include activity-based stops at Waterosity features full of songs, games, and narration.
The Washed-up Treasure Map is a hands-on, self-directed tour for families and kids. Using a treasure map, children will search for Waterosity exhibit features and report their activity by adding a wet thumb print to each point on their maps.
Heart of the Beast Puppet & Mask Theatre has created a suite of shows on the interaction of people, plants, and water. Presentations of Strawberries in Winter, The Lawn vs. the Prairie, and Ina Lotta Watta will be offered during the summer.
Water-Wise Living Tours
Each Saturday, there will be docent-led tours of the Harvest Your Rain exhibit, the Cutting Edge on Lawns exhibit, and plantings featured in Waterosity displays.
Go Green With a Splash Party
On July 11 and 12, the Minnesota Landscape Arboretum will be the site of the Go Green With a Splash Party with special Waterosity programming:
More detailed information on Waterosity will be available on the Minnesota Landscape Arboretum website (www.arboretum.umn.edu) on June 6.
Dittmann, C. 2008. Residential Stormwater Management: Guidelines for Analysis, Planning, Design and Implementation in Urban Landscapes. Master of Agriculture Final Project. Department of Horticultural Science. University of Minnesota.
Minnesota Green Roofs Council. 2007. http://www.mngreenroofs.org/
U.S. Environmental Protection Agency. 2008. What you can do to prevent NPS pollution. http://www.epa.gov/owow/nps/whatudo.html
May is a busy month with lots of gardening fun to be had. After a long cold winter, the excitement of getting out and enjoying our gardens feels like a reward.
Enjoy the many spring flowering shrubs (bridal wreath spirea, forsythia, lilacs, flowering almonds, etc.) and wait to prune them, if necessary, until after they are done flowering. Pruning them before they flower would ultimately most benefit the plant because they wouldn’t be investing their stored energy in new growth that would soon be cut off. However, after waiting this long for those beautiful flowers we don’t want to miss them!
New growth is starting on most of our herbaceous perennials. If one hasn’t cut back last year’s stems, now is a great time to do so before the new growth gets larger and interferes with removing the old growth. Come spring, last years stems tend to be more brittle and tend to be easier to remove than last fall. Many times pushing them a bit from side to side will allow them to cleanly snap at the base of the plant without even needing to physically cut them.
Continue to plant your cool season vegetable crops. This includes direct seeding of peas, spinach, and lettuce and planting of onion and cole crop (broccoli, cabbage, cauliflower, etc.) transplants. There are many different onion varieties on the market. One thing to try to look for are those that are long day adapted varieties. These develop and invest their energy into their bulbs as the days are long, like we experience in our Minnesota summers. There are also short day onion varieties that bulk up as the days get shorter. These typically do not perform that great here in Minnesota as by the time the days get shorter in fall the growing season is close to its end. Many of the onion sets we find for sale in stores are of short day varieties as these are easily grown in Southern states for us during the winter months. The will grow somewhat in size after we plant them here in Minnesota, but do not compare to the growth potential of adapted long day varieties. Many garden centers have little packs of seedlings of adapted long day varieties. Such varieties include: ‘Walla Walla’, ‘Mars’, and ‘Ailsa Craig’.
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David C. Zlesak, Ph.D.