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We have all admired the downy buds of pussy willows and magnolias. Branches sporting these unique, fluffy organs are commonly placed in floral arrangements. Gardeners watch the tips of their magnolias and willows each spring with anticipation of new growth and beautiful flowers. These unique structures are composed of two very important parts.
The Bud Scales are small tough little leaves with the very important job of protecting the plants growing point, or bud, from Minnesota’s cold winter temperatures and drying winds. Bud scales can protect young developing leaves or flowers. In order to do their job, these specialized leaves remain small and thick and form a tight case around the tiny bud. Water management is a very important part of the bud scale's work. The tiny bud must not be allowed to dry out or it could die. Bud scales develop a thin layer of cork bark that keeps moisture in, drying winds out, and has the added bonus of being inedible to most insects.
In addition to tough bud scales, pussy willows and magnolias have an added feature of a dense coating of hair-like Trichomes. This gives them their unique downy look. Trichomes have many functions in the plant world. They shade the plant from excessive sunlight, reduce water loss, deter insect pests, and shed fungal spores and dust. Some scientists speculate that the dense downy covering of trichomes on the flower buds of plants like magnolia and pussy willow may keep buds warm, allowing these plants to produce their flowers very early in the spring. This theory however has not yet been proven. No one knows for sure why some early spring flower buds are smooth and trichome-free, while others are as downy as a duckling.
Michelle Grabowski
In late March, when the snow finally melted away, many homeowners started to get worried about their lawns. As the temperatures have risen and rains have finally come, Minnesota lawns SHOULD be showing signs of life. If the brown, lifeless matt has not yet even a hint of green, an addition to the spring to-do list of ‘seed the lawn’ is probably necessary.
Typically, we recommend that lawns be seeded in the fall. In Minnesota, spring can also be a very good time to seed. There are many important steps involved in seeding or a lawn—that information can be found at the U of MN Extension website. One of the most overlooked steps in the process of seeding a lawn is selection of turfgrass species and varieties. Several cool-season grass species perform especially well as turf in Minnesota including Kentucky bluegrass, perennial ryegrass, tall fescue, and several fine fescue species.
Turfgrasses for Minnesota
In the northern United States, Kentucky bluegrass is probably the most popular turfgrass for home lawns. This species is used for parks, lawns, athletic fields, golf course fairways and many other sites. Under ideal conditions, the aesthetic quality of Kentucky bluegrass is second to none. The leaf texture and color of the species are very desirable. Additionally, this grass is able to survive harsh winters, can recover very quickly from damage, and has excellent mowing quality. Homeowners have the option of establishing Kentucky bluegrass as either seed or sod.
Kentucky bluegrass is a very popular turfgrass species in Minnesota. Bob Mugaas
Unfortunately, there are many negative qualities to this species. Kentucky bluegrass does not do well under severe summer stress—especially heat and drought. Most varieties of the species are not able to grow well in the shade. There are many diseases that can affect Kentucky bluegrass, and in order to achieve maximum quality, it requires high amounts of fertilizer and water. Contrary to its name, it is not native to North America, but came to America with early settlers. Kentucky bluegrass is oftentimes mixed with other species such as perennial ryegrass and the fine fescues.
Older varieties of the species are often referred to as ‘common’ types. These bluegrasses are characterized by the ability to grow in lower-input conditions; however, they have an upright growth habit and are more susceptible to leaf spot diseases. Newer varieties are referred to as ‘improved’. These bluegrasses are much better in aesthetic quality and often have improved disease resistance; however, they typically require a much higher level of maintenance. There are currently hundreds of varieties of Kentucky bluegrass available to consumers.
Snowmold disease on perennial ryegrass. Eric Watkins Perennial ryegrass is an excellent turfgrass under ideal conditions. The species germinates quickly and a lawn can be established quite rapidly, which is why it is included in many lawn seed mixtures. Much like Kentucky bluegrass, perennial ryegrass requires high levels of inputs in order to perform well and is classified as a high-input grass. Many varieties of perennial ryegrass contain endophytes, which are fungi that live inside the above-ground parts of the plant. These fungi produce compounds that are toxic to insects, thereby serving as a natural insecticide. Other benefits of endophytes include improved disease resistance and better summer stress tolerance.
The most negative characteristic of this species is its lack of winterhardiness. In fact, of the cool-season grasses that are used in Minnesota, perennial ryegrass is the least winter hardy. Because of the other options available for home lawns, perennial ryegrass should be used sparingly. At the University of Minnesota we are developing new varieties that will be better able to survive our cold winters. Unfortunately, these varieties are not yet available to the public.
When it was first introduced into this country, tall fescue was thought of primarily as a forage grass for livestock. The first variety used for turf was Kentucky-31, which was developed in the 1940s. This variety was quite coarse and light in green in color, so it did not produce an attractive turf; however, it did possess the ability to produce roots deep into the soil profile. This characteristic makes tall fescue drought avoidant—the species can perform better than most cool-season species during drought not because it uses less water, but because it can reach water deeper in the soil.
The first improved variety of tall fescue was released in the early 1980s. Current varieties of the species have finer leaves and a dark green color. Tall fescue is used in home lawns, athletic fields, golf courses and parks. The drought avoidance of tall fescue makes it a very desirable turfgrass for a home lawn. The species is also very tolerant of wear and there are very few diseases that are a major problem for it in the Midwest. Traditionally, tall fescue has been perceived to have a lack of winterhardiness. Recent research indicates that the primary reason for tall fescue death during harsh winters is prolonged periods of ice cover. Additionally, our research indicates that seeding tall fescue in the spring instead of the fall will reduce the risk of winter damage.
Note the differences in texture between Kentucky bluegrass and fine fescue. Bob Mugaas
Predator hard fescue. Eric Watkins The fine fescue species are strong creeping red fescue, slender creeping red fescue, hard fescue, Chewings fescue, and sheep fescue. The fine fescues are characterized by fine leaf texture, the ability to grow under lower-input conditions, and excellent shade tolerance.
The most commonly used fine fescue, strong creeping red fescue, is often mixed with Kentucky bluegrass in areas that are partially affected by shade. In the sunnier areas of the turf area, the Kentucky bluegrass will thrive, while in the shaded areas, the creeping red fescue will flourish. This fescue spreads quite easily due to its rhizomatous growth habit (it has spreading underground stems). The species does not perform well under dry and hot conditions and is susceptible to several diseases. This species is sometimes referred to as ‘red fescue’ or ‘creeping fescue’. Slender creeping red fescue is very similar to strong creeping red fescue but does not spread quite as rapidly.
Hard fescue is an excellent grass when there will not be high levels of stress from traffic and wear. The species does not grow very quickly, therefore, mowing is often reduced and requires very little fertilizer or water. While other grasses are struggling during periods of heat and drought stress, hard fescue often is still bright green and providing a usable turf. Chewings fescue is very similar to hard fescue and provides an excellent lawn with fewer input requirements than Kentucky bluegrass or perennial ryegrass. Although it is a bunch-type grass, it forms a very dense turf through aggressive tiller formation. Both hard fescue and Chewings fescue are under-utilized in Minnesota.
Sheep fescue is primarily used for no-mow areas such as hillsides, but can be used for higher-cut turf. The species is typically bluish-green in color and has a very nice appearance.
A species which is often sold for use as turf, but should never be purchased is annual ryegrass. This grass is often sold in mixes that are to be used for quick establishment or repairing bare areas due to its very quick germination and establishment rate. The important thing to note about annual ryegrass is the ‘annual’ in its name; the desire of most homeowners is a lawn that will last for years, not months.
Now What?
One of the most frequent questions I get asked is “When I go to my local retailer, I have very limited selection. How can I find out which grass I should buy and where can I buy it?” The first part of this question is quite easy to answer while the second part is a bit more difficult.
The University of Minnesota tests hundreds of different turfgrass varieties each year. We report all of our findings on our turfgrass science website in the ‘research’ section. Each variety is rated for important characteristics such as spring green-up, color, density, disease resistance, and overall turfgrass quality. The National Turfgrass Evaluation Program sponsors similar testing sites throughout the country. The NTEP website is another great source of turfgrass variety data. Although regional and national data can be helpful, data from Minnesota will be the most applicable.
Once a variety has been selected, it is often difficult to locate a supplier. Local nurseries and seed distributors may be able to locate sources for most varieties. Many varieties are also available for purchase over the internet. When it comes to grass seed, you almost always ‘get what you pay for’. The extra cost is typically worth the better performance and longevity of a high quality lawn. Finally, only named varieties should be purchased—always avoid any seed that does not have a variety name or is labeled ‘VNS’ (variety not stated).
I hope that your lawn is in great shape and this information can be filed away for future years. If your lawn needs to be seeded this spring, an hour or two spent looking at variety data will be well worth your time.
Learn more
The University of Minnesota currently has two excellent online educational opportunities for those interested in learning more about lawns:
Rain barrel setup at the author’s home. Rebecca Chesin
One of the latest gardening trends still gaining popularity is the use of rain barrels. Of course, collecting rain water for irrigation has been done by people for centuries. In these modern times, several forces have led to a resurgence in their popularity and several new twists to this age-old practice.
Here are some of the top reasons to install rain barrels:
Dipping in a Toe
A faucet will make acquiring water more convenient. Rebecca Chesin
Rain barrels are a seasonal product in Minnesota. Since their use has been increasing, many stores carry them during the growing/watering season. Check garden centers and nurseries as well as do-it-yourself, home improvement, and hardware stores. There are online shopping options, but shipping can be expensive. Consider building your own to save money. It can be done in about 1 hour (once you have the supplies) and, depending on your setup, can cost under $50 per barrel.
Make sure you are using a quality design and products. You’ll want to have strong, well-matched connections so the barrel doesn’t leak. A screen to cover open water is important to keep your barrel from becoming a breeding ground for mosquitoes. You could also combat mosquitoes by treating the water, but a screen also has the advantage of guarding against small animals, leaves, and shingle debris from falling in.
Accessorizing Your Rain Barrel
Consider where you will place a rain barrel. Remember, the water pressure is going to come from gravity (unless you dip watering cans into the barrel or use a pump). If you attach a hose to the faucet to empty water through, raising the end of the hose until it is as high as the water level in the barrel will cause the flow to stop. Some people set their rain barrels up on bricks or cinder blocks so the additional elevation will help the water flow. If you do this, make sure your support is steady and strong; 55 gallons of water weighs over 450 pounds!
Think about whether one barrel will be enough. You can connect barrels in series. Fifty gallons of water might seem like a lot, but most people seem to find they “outgrow” that meager capacity in a short period of time.
Barreling Through the Year
Your biggest decision will be what to do with your barrel during winter. Different manufacturers probably have different recommendations for our part of the country. A friend of mine, whose rain barrel is off the corner of her garage, (and so, not near the house’s foundation) simply opens the faucet so any water can drain out instead of accumulating in the barrel and possibly bursting the barrel when the water freezes solid.
A rain barrel can be as straightforward as a whiskey barrel and a water-proof liner. Amy Loomis
My barrels are the do-it-yourself variety, made in 2003 when there wasn’t much information about best practices for using rain barrels in areas with harsh winters. I was concerned about wear-and-tear on the materials and connections during freeze-thaw cycles, so I remove the barrels in late fall and re-attach the lower half of the downspout. In the spring I set the system up again. This might create a winter storage problem for some households. Next winter, I think I’ll experiment with a short length of hose connected to the faucet to carry any water a safe distance away from the basement.
Another decision will be where to place your barrel, and how to accommodate it at the downspout. I’ve seen various diverters that connect into the downspout so when the barrel becomes full, additional rainfall is channeled back to the original downspout and out into the yard. That would also address the winter issue. So far, I haven’t heard any reports about trying these options in a climate similar to ours.
During the summer, your barrel will likely grow algae, especially in a sunny spot, kind of like a Minnesota lake during a hot, dry spell. There are treatments you can add to the water to inhibit this (try pond or gardening stores for additives that are safe for your plants). Personally, I don’t bother. It has not negatively affected plant growth and perhaps the plants are getting a little extra boost of nutrients. At the end of the season, I take a long car wash brush and clean out the barrel so it’s fresh and ready to go in the spring.
Important Note: Although it is strongly recommended to use food-grade plastic barrels that did not contain toxic substances, there is no consensus about the safety of using rooftop harvested rainwater for vegetables and other plants. Roofs contain all sorts of materials that rain will wash off into your barrels: dust, plant matter blown by the wind, bird droppings, and bacteria. In addition, some roofing materials are made from petroleum products, and so on. To paraphrase a famous adage: Caution is the better part of good health.
In a time of increased consciousness about the environmental impact of our actions, the growing scarcity of clean water, and the implementation of watering restrictions—rain barrels are not just fun—they are a good idea. Have fun installing your own this spring!
Editor’s note: Rebecca Chesin has been a Master Gardener since 2004, when a Plymouth City grant for alternative landscaping re-ignited her passion for gardening. Her and her husband collect rainwater in 8 55-gallon barrels and have led several rain barrel demonstrations and hands-on sessions. Read more about Rebecca’s rain barrel project, including some tips on how to build your own and a rainfall calculator at: http://tinyurl.com/2t8h9p.
Winter injury on dwarf Alberta spruce. Michelle Grabowski 
Winter injury on yew. Michelle Grabowski
Winter injury on a dwarf white cedar. The undamaged portion of the plant was below the snowline. David Zlesak
As the weather warms and gardeners venture out to rediscover their yards, many are aghast to find that their evergreen shrubs are not so green. This past winter’s sunny days at temperatures well below freezing combined with cold winter winds have taken their toll. Yews and the ever so popular dwarf Alberta spruces have been particularly hard hit this year, but any evergreen in the wrong location may be suffering.
What has happened to these poor shrubs? Although one would think that a small cold shrub would be grateful for the warm sun on a particularly cold day, the combination of hot sun rays with freezing air and soil temperatures can be disastrous. On sunny winter days, evergreen needles can be injured in several ways. As needles warm up in the sun, they become active and lose water to the air through transpiration. In the warm summer months the roots would quickly replace this depleted water. In the winter months however, roots are frozen in the ground and cannot replace the evaporating water. The needles quickly dry out and turn brown. When the sun finally sets, the temperature drops quickly and the water inside the active needles freezes and kills the delicate plant cells. The result is rusty brown needles on part or all of the plant.
Plants that are facing south or west or those that are exposed to cold winter winds tend to be especially affected by winter drying. Often these plants look half brown and half green, since only one side of the plant is directly hit by the wind and sun.
Unfortunately there is not much that can be done to undo the damage we are currently seeing on evergreens. Dead needles and branches can be pruned off, but it is advisable to wait until mid spring before seriously pruning back any winter-injured evergreens. Although the brown needles themselves are unlikely to recover, the buds resting along the branch are hardier and may have survived. Wait until the buds have opened and started to grow. Then carefully examine the affected areas of the plant and prune back to the next healthy bud.
When choosing evergreens at the nursery this year, select an evergreen that will be well-suited to the specific environmental conditions of your yard. Yews, arborvitae and hemlocks are very sensitive to winter injury and should not be placed in exposed, full sun locations. Remember that all new transplants will be more susceptible to winter injury until their root system is fully established. Proper planting and watering of new shrubs and trees is the first step in protecting them from future injury. For more information about ways to protect trees and shrubs from winter injury next year read the University of Minnesota Extension publication ‘Protecting Trees and Shrubs against Winter Damage’.
Emerald ash borer killed trees. Jeffrey HahnBy now, most, if not everyone, has heard about emerald ash borer and the threat it represents to Minnesota’s large population of ash in our urban landscapes and forests. This exotic beetle attacks all species of ash in North America, including green, black, and white ash as well as all sizes from small, 1/2 inch diameter to large mature trees. Emerald ash borer prefers stressed ash but can also successfully attack healthy ones as well. Unfortunately, our ash trees have little or no resistance to this insect which means effectively that no ash tree is safe from this invasive species.
Emerald ash borer is currently found in seven states in the U.S., Michigan, Ohio, Maryland, Indiana, Illinois, Pennsylvania, West Virginia, as well as Ontario Canada. It has not been discovered to date in Minnesota. This beetle only travels about 1/2 to 2 miles on its own each year which would take this insect decades before it could reach Minnesota on its own. However, emerald ash borer is artificially spread by people when it is accidently transported in ash firewood, nursery stock, and wood objects, like planters. It’s not a matter of if emerald ash borer will be found here, but when will it be discovered in Minnesota. That is, unfortunately, a question no one knows the answer to.
With all the uncertainty over emerald ash borer’s arrival and how devastating it will be once it gets a foothold here (think Dutch elm disease, only worse), Minnesotans wonder what they should or should not be doing until it actually gets here. The following are answers to some of your most common questions.
Emerald ash borer. Jeffrey Hahn
Emerald ash borer D-shaped exit holes. Jeffrey Hahn
Emerald ash borer galleries. Jeffrey HahnWhat does emerald ash borer look like?
It is a relatively slender beetle, iridescent green with a somewhat coppery colored head that measures between 1/3 - 1/2 inch long. There are several other insects that are also green that can be confused with emerald ash borer, especially the six-spotted tiger beetle and polydrusus weevil. There are also native borers associated with ash that could also be confused with emerald ash borer. For more information on look-a-likes and native borers, go to the Minnesota Dept. of Agriculture web site.
How do I know if my tree in infested with emerald ash borer?
It is difficult to diagnose an ash tree that infested with emerald ash borer. The first symptom is dieback in the tree’s crown. You have to be careful as there are other problems that can cause dieback in ash trees. If you see dieback, look for the characteristic D-shaped exit holes in the trunk and branches. Emerald ash borer also creates a characteristic series of S-shaped criss-crossing tunnels, although this is under the bark and normally not visible. Although not definitive, woodpecker activity, bark splitting, and epicormic shoots can indicate possible emerald ash borer infestation and should raise red flags to signal you look more closely at the tree. Click here for more information on symptoms.
What should I do if I think I have an emerald ash borer problem?
First be sure you have an ash tree (ash tree ID pdf) and emerald ash borer symptoms. If you are still not sure, contact a certified arborist, your local extension office, or other trained professional. If you still suspect emerald ash borer, contact the Arrest the Pest Hotline immediately. In the metro area call 651 201 6684 or 1 888 545 6684 if you are in greater Minnesota. You can also send an e-mail to Arrest.The.Pest@state.mn.us
Is there anything I can do to help keep emerald ash borers out of Minnesota?
Don’t transport firewood, even if it is within Minnesota. Buy the wood you need locally from an approved vendor. Don’t bring an extra wood home with you, burn it all at that site.
Should I treat my ash for emerald ash borer now?
No. The Minnesota Dept. of Agriculture currently has a very active monitoring program to detect emerald ash borer and so far it has not been found in Minnesota. While there are insecticides available now to both professional landscape applicators and home owners for treating borers in trees, as long as emerald ash borer is not found in Minnesota, it is unwarranted to treat your ash for emerald ash borer unless it has been found within 15 miles of an known infestation. Once, emerald ash borer is established, insecticide treatments may be an option for high value ash trees.
Should I still be planting ash trees?
Ash already makes up a large percentage of the urban and rural trees in many Minnesota communities. Many areas of the state are at particular risk where ash is concentrated. Planting additional ash only exacerbates this situation increases our vulnerability to emerald ash borer. While there may be a few cases where there are extenuating circumstances, in the vast majority of cases, alternate tree species should be considered for planting. For alternatives to planting ash in your area, go here.
Should I take out my ash tree now before emerald ash borer gets here?
If your ash is healthy and vigorously growing, there is no reason to remove it now. If, on the other hand, your ash is declining and requires a lot of care you should consider not putting any major effort into its maintenance and eventually taking it out of your landscape. As you remove ash be sure to create a diverse landscape when you replant trees and shrubs.
Nightcrawler. Dept. of Entomology, University of MinnesotaThis is the time of year when nightcrawler activity can become obvious in your lawn. Nightcrawlers, a type of earthworm, become active as soon as the weather warms up. They feed at night on organic matter in the soil and deposit castings, i.e. soil and waste material, on the soil surface. These casting can become hard and can make a lawn uneven and sometimes difficult to walk on. Still, in the big scheme of things nightcrawlers are just a nuisance.
In fact, nightcrawlers are very beneficial. They help break down thatch and other organic matter and mix and recycle nutrients back into the soil. Their tunneling greatly helps water and air penetration into the ground. When there is an imbalance between the presence of organic matter and its breakdown, this can lead to an increased amount of thatch. An excessive thatch layer reduces water infiltration, decreases the penetration of pesticides and fertilizers, and can make turf grass more susceptible to heat, drought, and plant diseases.
What should you do if you have a nightcrawler problem? The use of insecticides is strongly discouraged. First, there are no insecticides that are labeled for nightcrawlers. Second, insecticides labeled for lawn applications are typically very hard on nightcrawlers reducing their populations to unacceptably low levels. Because of their value to lawns, you should tolerate nightcrawler presence in your yard.
Is there anything you can do to reduce the nightcrawlers castings in your lawn? Possibly. One method that people think of is to take a roller and flatten out the bumps. This is generally not very effective, especially when the ground is dry. Your best bet is to try to roll them when the ground the wet. However, also consider that you are compact the soil as you do this. Rolling your lawn once or twice will probably not negatively impact your lawn but if it is done on a consistent base you will do more harm than good.
Another option is to power rake your lawn. This is usually best done in the fall. It is also possible to power rake in early spring (late April/early May depending on where you are in Minnesota). If you power rake later in the spring, it is important to either overseed that area or apply a pre-emergent herbicide to prevent annual weeds from sprouting.
Early May usually marks the beginning of the lawn mowing season. With our cooler than normal temperatures, lawn grasses have been a little slower to resume the more rapid growth rates typical of this time of year. Before the first mowing:
Crabgrass Control
By early May, we can begin thinking about getting our crabgrass weed control products applied. Again, with the cooler than normal temperatures this spring, early May should not be too late for an application of a crabgrass killer even on our lighter, sandy soils or south and west exposed sites. Heavier soils are frequently wetter and cooler and hence take longer to warm up. Therefore, application of crabgrass preemergence herbicides on those soils can usually be delayed until later in May. Remember to water in these products with about 1/4 to 1/2 inch of water following application as this will help move the product down to the soil surface, which is the area of actual crabgrass control.
There continues to be more and more interest in the use of organic products in home lawn care programs. Corn gluten meal (10-0-0) can be one of those organic products that provide both some nitrogen fertilizer and some preemergence herbicide effect, particularly for annual weedy grasses such as crabgrass. Early to mid May is a good time for the first application of the product. Typically a second application is put down around early to mid August. There are now several brand names available through various retail gardening outlets.
Check for Thatch Buildup
If your lawn appears to be very slow to green up this spring, it is likely due to cold soil temperatures. In reality, only warmer, sunny conditions will help raise soil temperatures enough to encourage more vigorous growth and green up. However, it may also be an indication of too much thatch. Thatch is the brown fibrous mat that exists between the soil surface and the where the grass shoots begin to be visible. It consists of both living and dead material and if this thatch layer gets much above 1/2 to 3/4 of an inch, it can begin to cause a number of problems, not the least of which is slow spring green up and growth. This thatch layer acts much like an insulating blanket reducing the sun’s energy that reaches the soil surface and hence soils are slower to dry out and warm up. For information on how to diagnosis, relieve and/or manage thatch problems, see University of Minnesota Extension Factsheet: FO-01123.
Snapdragons are tolerant of cool weather. David Zlesak Spread out your planting schedule- plant cool season crops early in the month and warm season crops until later in the month or in June.
Warm season or tender species do not tolerate cool temperatures well. Temperatures below 50°F can cause chilling injury. The colder the temperature and the longer the exposure, the more injury can occur. Symptoms of chilling injury include stunting, wilting, death of leaf margins, and, if severe enough, death of the whole plant. Chilling injured plants take time to recover. The benefit of trying to extend the growing season with early planting of warm season crops like tomatoes can be lost.
Cool season crops that can tolerate lower temperatures and even light frosts include: calendula, cole crops (i.e. broccoli, cabbage, and cauliflower), dianthus, diascia, larkspur, pansy, peas, primula, snapdragon, stocks, and sweet peas. Warm season crops that can easily suffer from chilling injury and are best planted when night temperatures are routinely at least in the 50’s F include: begonias, cannas, cucumbers, impatiens, melons, peppers, pumpkins, and tomatoes.
Watering bags can help with newly planted trees because they allow water to slowly seep in over several hours and runoff is avoided. David Zlesak
Spreading a layer of mulch and then planting through it can save time and simplify the process especially when using smaller transplants. David Zlesak
Water especially newly planted trees, shrubs, perennials, and bedding plants regularly. Water deeply and as needed so the soil remains moist, but is not soggy.
Consider applying a fresh layer of organic mulch in planting beds to replace what has broken down and to give your landscape a fresh appearance. Mulch has many great benefits including helping to retain moisture, reducing weeds, keeping the soil temperature even, and providing nutrients after it breaks down. There are many mulch options including decorative wood and bark mulches, rougher wood and bark mulch from tree trimming and removal companies, cocoa bean hulls (they emit a chocolaty scent), tree leaves, and hay and straw. Recommended mulch depth varies depending on mulch type and ability for oxygen to penetrate it and reach the roots. Coarser mulch with a relatively low nitrogen content like wood and bark are typically applied a few inches deep, while finer mulches like cocoa bean hulls and grass clippings are best applied only an inch or so deep.
May is a great time to fertilize herbaceous perennials, shrubs, and lawns. Fertilizer contains essential elements that serve as ingredients plants use to build molecules and contribute to efficient metabolism and growth. Fertilizer is typically best applied after plants begin to grow. At this point they are growing fast and increasing energy reserves from photosynthesis to efficiently utilize these elements. In addition, extra early applications of especially nitrogen can be detrimental because it can stimulate very vigorous growth before the weather is appropriate resulting in tissue that is more prone to damage by a late freeze or disease.
There are many different fertilizer formulations and options in the marketplace. The three large numbers on the fertilizer container signify the percent by weight of nitrogen, phosphorous (as P2O5), and potassium (as K2O)- the three essential elements used in the highest quantities besides carbon, hydrogen, and oxygen (plants primarily receive those from water and carbon dioxide). Most Minnesota soils have sufficient phosphorous and formulations of especially granular fertilizer for general purpose or lawn use are available now that are low or devoid in phosphorous. Low phosphorous formulations are becoming increasingly available due to legal and voluntary efforts to combat pollution from phosphorous runoff.
Having a professional soil test done is well worth the investment. It takes the guess work out of understanding your soil and fertilizer needs. A professional soil test will tell you your current nutrient levels and pH and provide recommendations for amendments to get your soil within the appropriate range for the plant materials you would like to grow. The relatively low price of a soil test makes economic sense. Information learned from a soil test allows one to purchase and apply just what is needed. Too little or too much of any essential element can lead to poor growth. Providing proper nutrition leads to improved plant growth and avoids pollution. Visit the University of Minnesota Soil Testing Laboratory website to learn more.
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Happy gardening!David C. Zlesak, Ph.D.
Editor
Extension Educator