What am I and what do I turn into? I am a spiny elm caterpillar, Nymphalis antiopa. I prefer to eat the leaves of elm and willow, but you can also find me on a variety of other hardwood trees including birch, hackberry, linden, cottonwood, and poplar. I am easy to identify from my black body with many tiny white spots, the seven or eight red spots running down my back, and my conspicuous branched spines. I hatch from eggs laid in the spring and feed in May and June for about five to six weeks, growing to two inches in size.
I turn into a morning cloak butterfly, a moderate sized insect with a wingspan of two to three inches. My wings are dark brown with a row of blue spots and a creamy yellow band along the edge of them. I am one of the few butterflies that overwinter as an adult, so I am one of the first butterflies you will see in early spring. Look for more caterpillars from a second generation in July and August. My larvae from the second generation finish feeding at the end of the summer in time to pupate and emerge as adults by fall. Such butterflies find sheltered areas, e.g. under leaves, to spend the winter.
People talk a lot these days about how kids sit in front of computers and don’t get out and enjoy the outdoors the way they used to. There’s certainly some truth in that sentiment. However, there really is a lot one can do to get kids excited about nature and gardening. As a children’s education instructor at the University of Minnesota Landscape Arboretum, Kim Kube knows that the best way to get kids excited about something is to minimize talking and maximize opportunities for learning by doing. Otherwise, they’ll quickly get bored and you will, too.
Kube is always coming up with new interactive gardening projects for kids ages 5 to 14. Projects don’t need to be elaborate to be fun and educational. Her advice is to “do things kids naturally like to do.” Watering is always a popular activity. But kids also love planting things, looking for insects (“bugs”) and digging in the soil (“dirt”) to see what they can find.
Explanations should be tailored to each age group. If you’re doing a planting project with young children, for example, take things step by step. As they follow along, you’ll need to explain how to dig a small hole, gently remove the plant from its pot, put the plant in the ground, and water it. Once they’re finished and admiring their work, it’s fine to briefly tell them things like how plants gather food from the sun and soil. However, save big words like photosynthesis for older kids who can better understand the concept.
Understanding how things work is a big thing for kids of all ages. You can explain all you want what will happen to a plant if you don’t water it, but having kids conduct an experiment to see what happens if they don’t water their plants for a week helps them make the connection in a concrete way. Of course there’s also the popular science project that we all did in school where you put seeds in a plastic bag with a wet paper towel and periodically unroll them to watch them grow. This is not only fun, it helps kids see a process they’d normally only get to see in a book.
If asked what will happen if a plant gets stepped on, Kube often tells kids to try it and find out. This kind of exploration helps bring out everyone’s natural curiosity, prompting them to ask their own questions like: What do the leaves do? What does the stem do? And how about the roots? Depending on the age group, these questions can best be answered with simple demonstrations and experiments, such as coating the backs of a plant’s leaves with petroleum jelly to illustrate what happens when a plant goes without air.
When it comes to bugs (and you know it always does if you’ve gardened with children) some kids love them and others are scared to death of them. Though evidence of injury is hard to come by, lots of kids believe that earthworms bite. Convincing them otherwise takes, well, peer pressure. Kube always keeps an eye out for the kid who loves bugs in her classes. There’s always at least one. That’s the kid she hands the worms to, or the ladybugs, whatever the bug of the day may be.
Spend some time talking up the great work earthworms and ladybugs do in the garden and, eventually, even the kids who are afraid will be curious and gather around the brave bug-holding child to see what’s happening. Most wind up holding out their hands to hold the bugs, too. Kube explains to everyone about the work that worms and other decomposers do in the garden. She encourages kids to name the worms they find in the dirt. That way they form more of a connection with creatures, making them less likely to be afraid or try things like seeing how far they can stretch before they pull apart.
Kube eases kids’ fears about bugs that really do bite or sting by talking to kids about the important roles they play in the garden. “Bees aren’t really on a mission to sting you,” Kube tells them, hoping to stop all the squishing of bees and other bugs that kids do. They’re really out in the garden helping to pollinate plants. And while spiders may seem scary, they do a great job of eating mosquitoes. “And less mosquitoes for a few spiders usually seems like a good trade for most kids,” Kube says.
If you take kids to a public garden, it helps to know what’s already there. That way you can answer their questions as you go. Kids will invariably ask about plants they like or plants that look weird to them in some way. Stopping by a pond is always a good idea because kids love water and there’s usually plenty of creatures and plant life to see and talk about. Try scooping up some water in a clear cup in a few different spots and see what you find. Be ready to talk about things like tadpoles, frogs and dragonflies because you’ll definitely get questions about them.
“Sometimes, though,” Kube says, “it’s the simplest things that make the best lessons.” It’s amazing how much kids notice if you just spend some time sitting with them under a tree looking up at the leaves, the trunk, and the branches. If you’d like to see an area cleared of dandelions, have a quick contest to see who can dig up the dandelion with the longest root and then explain how dandelions grow and go to seed. Or just take kids outside and give them time to dig around in the dirt. When Kube does this, she’s often amazed at how kids can focus on the smallest things. “They’ll find bugs and just bring them up to me,” she says. “They want to know all about what they find and they see things that adults never even notice.”
The story of Johnny Appleseed (a.k.a. John Chapman; 1774-1845), a legendary man who wandered around planting apple seeds, is one most of us have heard growing up. Anyone who has ever really looked at an apple probably automatically wonders, where did he get all those apple seeds? There are only up to about 10 seeds per apple (amount depends on efficiency of pollination). They are inside the core of the fruit and somehow need to be removed. So who ate all the apples to get enough seed for him to plant trees for 40 some years?
The answer is wonderfully simple. Johnny got all of his seed from the cider mills. The mills pressed the apples to make cider and he collected the seed as it flowed out into the river. The cider mills let him have the seed for free since he was planting trees that would someday hopefully bring more apples to the mills. Johnny wasn’t just a wandering seed caster, he was a nurseryman. He bought tracks of land, fenced them with log fences, and planted his seed. He paid those who lived nearby to tend the trees for him and moved on to plant more trees in the next plot. The trees were eventually sold for 6 cents a piece.
So where do the trees we see for sale come from today? The guy to ask is Bob Arntzen, fondly known as “Seed Bed Bob”. Bob plants tree and shrub seeds for Bailey Nurseries; and has done so for 35 years. Bailey Nurseries is a large wholesale nursery based out of Minnesota and has been in business since 1904. Bob is a shy encyclopedia of growing knowledge (pun intended). Bob is our modern day production oriented version of “Johnny Appleseed”.
Bob grew up in St. Paul Park and took a summer job with Bailey Nurseries when he was only 13. Like Johnny, he loves to work outside. At first he was busy hand planting in the field, weeding, pruning trees and “budding” (form of grafting) plum, apple and ash trees. Eventually Bob started accompanying Pat Perkins, who was a neighbor and foreman at Bailey Nursery, to collect seeds for trees and shrubs. They studied tree and shrub specimens and picked those with the best characteristics to collect seeds from.
Bob loved his work and after high school he attended the University of Minnesota. He started out in the Forestry Program, but at the time there were more opportunities in Nursery Management, so he switched majors. The draft hit and he spent two years in the army. The week he got back from the army he was back at Bailey’s. That would be the fall of 1970. He started in greenhouse propagation…and of course back in the day these were glass greenhouses with sand benches. He propagated hard and soft wood cuttings including evergreens.
While he enjoyed his work, the army must have given him a sense of adventure, because he took off for about 4 months to see Europe before settling back at Bailey’s, this time with Don Nordine in the seed beds. Bob spent three years as Don’s assistant learning tree and shrub production. In 1973 Don retired and Bob stepped into his boots. So for 35 years Bob has been collecting and storing seed; giving seed treatments; preparing the beds and planting; warding off spring freezes that could damage emerging seedlings; growing the trees and shrubs and then harvesting and grading them.
Bob grows somewhere around 100 varieties of trees and shrubs for Bailey Nurseries from seed. He collects most of that seed from specimens the twin cities area, though some seed is collected from farther away. He looks at the characteristics of trees and seed quality and quantity. He knows off of the top if his head information like how many seeds of each variety make a pound. The smallest seed he works with is the size of a pencil dot. It is an Aspen and can you guess how many seeds per pound? Yup, it is a whopping 3.6 million seeds! The largest seed is a black walnut, which is roughly between the size of a quarter or half dollar. How many to the pound? That would be 40.
How long is a seed viable? That’s a great question and it depends on the seed. Oak acorns rot fairly easily, whereas apple seed is easier to store. Seeds of Populus sp. (poplar and aspen) need to be planted fresh, whereas Kentucky Coffee tree can take years to germinate without a little coaxing. The science of seed storage and germination is fascinating and complex.
Bob started out in the seed beds in Hastings, Minnesota and new seed beds were developed at the Nord Farm in Cottage Grove, Minnesota in 1981. Each seed has a “best time to plant” which varies from spring to fall, (Bob scatters between 50-60% of these seeds by hand). Each seed has a different depth it needs for optimal germination. Each seedling needs to be protected from late frosts. Each tree needs water, fertilizer and the correct soil conditions to thrive.
There are long days spent collecting, preparing (for example the wings on the maple seeds need to be removed), storing seed; then preparing the fields; sowing the seeds; covering them; monitoring moisture; weeding, and frost protecting. When asked what his favorite part of growing trees and shrubs is, Bob says he enjoys collecting and preparing the seed; but to watch the miracle of new seedlings emerging from the soil, makes all the hard work worth it. In his 35 years of planting trees and shrubs for Bailey Nurseries Bob has planted easily between 90-100 million seedlings. Not even Johnny Appleseed can hold a candle to Bob Arntzen! Bob was recently honored with the JV Bailey award for his many contributions to the nursery. Thank you Bob for starting many of the trees and shrubs we enjoy here in Minnesota landscapes and beyond!
In Minnesota three species of hydrangea commonly grace our landscapes- smooth hydrangea (Hydrangea arborescens; e.g. ‘Annabelle’), panicle hydrangea (H. paniculata; e.g. ‘PeeGee’, ‘Tartiva’, and ‘Unique’), and bigleaf hydrangea (H. macrophylla; e.g. ‘Endless Summer’). Each species has its own unique growth pattern, and there is variability among cultivars for especially size and structure of the inflorescence (flower clusters) and color of the large, showy, infertile florets. One spectacular hydrangea that has captured the imagination of many Minnesota gardeners over the years is climbing hydrangea (H. anomala subspecies petiolaris). Just some understanding of its basic requirements will allow most people to successfully grow this impressive species.
Climbing hydrangea rivals the best of the ornamental vines for beauty. It is native to China and Japan, relatively pest free, and is reliably hardy to zone 4. The attractive, glossy foliage is an attractive backdrop for the large, lace cap, inflorescence, typically a foot or more in diameter. Even when not in flower, the foliage of climbing hydrangea is very ornamental and makes the plant worth growing. The flower buds are set the previous growing season and typically open in late May into June. Climbing hydrangea is one of the earliest flowering hydrangeas in our area. Interest continues after the fertile florets are spent as the large white sterile florets, borne around the perimeter of the inflorescence, persist throughout the summer.
The large main stems of climbing hydrangea have a strong tendency to grow vertically and have modified roots that adhere tenaciously to buildings or tree trunks. Shorter secondary stems growing from the main stems produce the flowers. These stems often lack the modified roots for support. The plant eventually grows into to dense, well-foliated vine capable of covering structures and reaching heights of 20 feet or more. Besides the very attractive foliage and flowers in spring and summer, climbing hydrangea also provides great fall and winter interest. After the leaves drop, the beautiful cinnamon-colored, peeling bark and network of coarse stems are exposed.
Although climbing hydrangea has been routinely sold for decades in Minnesota, there are relatively few mature, flowering specimens that can be found. The key to success with climbing hydrangea is providing it with a suitable site and patience. Plant climbing hydrangea in full sun to partial shade and soil that is moist, rich, and well-drained. Avoid digging around the plant and disturbing the root system, as this can significantly stunt growth. It is slow to establish and may take several years before it begins to reliably bloom. Frequently, impatient gardeners give up and replace it before it has a chance to become established. Once established, it can grow a few feet or more in a season and be covered with hundreds of large, attractive inflorescences. A little planning, appropriate placement, and patience are the key factors required to be successful with this impressive, relatively easy to grow climber.
Homeowners are reinvesting in their properties rather than building new homes and moving on. Urban parks are being renovated as aging facilities and pavement are declining from years of Minnesota weather and heavy use. Parking lots and restaurant patios are being torn up and reconstructed in order to provide more desirable outdoor dining areas or reduce the amount of storm run-off water. So, where does that leave the trees that have managed to survive the years of assaults and are actually providing some environmental and aesthetic benefits? Many are summarily removed or are severely damaged during the reconstruction and subsequently die. Fortunately, there are more options than those two.
More trees are damaged and/or die each year from construction activities in landscapes and streetscapes than in new subdivisions built in wooded areas. The most common reason for tree damage and mortality is root loss. Root loss may be a direct result of construction, such as digging trenches for utilities or foundations, regrading the lawn (i.e., raising or lowering the grade), or deep roto-tilling the landscape in preparation for a new lawn or planting. Indirect root loss is just as common but a bit more insidious. Soil compaction from construction equipment or vehicles driving over the root systems, elevated soil pH from burying debris (especially paint, mortar, plaster or concrete), or washing out concrete truck chutes in the landscape all eventually kill roots. They do so by reducing soil oxygen, water, and nutrient availability or from the direct chemical toxicity of some of the buried materials.
There are materials and techniques that allow projects to be completed without creating a tree un-friendly environment. Predicting the potential damage to tree roots and avoiding or lessening that damage will in the end result in more healthy trees shading the landscape.
Hardscapes in the landscape are often essential, yet are often the most common and predictable causes of tree root damage and tree mortality. The materials used for sidewalks and patios are generally less of an issue than the techniques used to construct them. An experienced hardscape contractor will stress the importance of preparing a solid base for walkways and patios, as it should be. Without a solid base, the sidewalk or patio will be more prone to heaving and rupturing of the surface.
Base preparation usually involves excavation of at least 6 inches of the topsoil and then compaction of the installed base material, often sand, gravel or a mixture of the two. If the patio or sidewalk is under the dripline or within the critical root area* of a tree, the direct loss of a significant number of roots is inevitable. Most tree roots are within the top 3 feet of the soil profile. Most fine roots, those roots that absorb the majority of water and minerals required to sustain life, are within the top 12 inches of the soil profile. If the landscape soil is a compacted clay, the root system will be even more shallow. If the soil is a well-drained sandy soil, the roots may grow a bit deeper.
*The Critical Root Area of a tree can be calculated as follows: measure the diameter of the tree trunk (in inches) at a height of 4.5 feet above ground. For each inch of trunk diameter, 1-1.5 feet of radius is considered the critical root area. So, for a tree with a 10 inch trunk diameter, the distance from the trunk to protect would be 10-15 feet. Roots within this area are considered to be the most important roots for tree health and longevity.
Root loss can be minimized during base preparation…easily minimized. Two practices need to be modified to avoid damage. (Actually, there is one other practice that works even better…don't build sidewalks and patios within the critical root area of trees, but that's usually not a very practical recommendation.) The first recommendation is to avoid the damage by not excavating. That may seem like a typical, academic recommendation but on second thought it may be the perfect solution for someone who wants a sidewalk yet loves the landscape trees above it.
Bases can be built above grade rather than below grade and it's done all of the time. Since organic matter can't be compacted, the sod will need to be stripped. Remove the sod and 1-2 inches of soil with a sod stripper, not a tractor with a front end-loader. Voila! Hardly any roots have been lost so far! Then, install the edging material for the hardscape and the base material (sand, gravel, mix). Compact the base and install the surface material. Direct root loss has been minimized due to the minimal excavation. Indirect root loss has been minimized due to the compaction of only the sand/gravel base, not the sub soil. Even a compacted sand/gravel base allows water and oxygen to penetrate, so there's very little harm done to the root system.
To minimize the direct root loss even more, completely avoid excavation and install a wooden patio or sidewalk. Raised decks rely on a few posts sunk into the ground, connected to each other by joists that support the decking material. Instead of building a deck 10 feet above ground, build a patio or sidewalk 6 inches above ground. Same construction principles, just applied to a different hardscape.
The second practice that needs to be modified involves the type of equipment that is used to build the hardscapes or deliver the materials. Do not allow trucks, tractors or any other heavy equipment to freely use the landscape as one big highway or parking lot. If a truck or small tractor is allowed to drive over the critical root area of a tree more than a time or two, the soil can become impenetrable to oxygen, water and roots, especially if there's any clay in the soil. The result is indirect root loss…unnecessary, stupid, indirect root loss. Don't do it. Modify the practice.
Designate one traffic pattern and one storage area, preferably away from the critical root area. If the traffic or storage area will impact the critical root area, soften the impact and prevent the compaction by covering the soil with weed barrier fabric. Cover the fabric with at least 6 inches of coarse wood chips. This is the best way to avoid compaction. After the construction is completed, remove the wood chips (don't use a big tractor to scoop them up, please), remove the fabric and re-seed the lawn.
There are some excellent hardscape materials that do not deny the roots below of the water, oxygen and minerals they desperately need to live: porous pavements. In Minnesota, several porous surfaces have been successfully used that have stood the test of time and winters very well (at least as well as traditional concrete and asphalt). Porous pavers, either clay brick or concrete pavers laid "dry" over a gravel base are the most common. Rather than a solid, impervious surface that is mortared together over a concrete base, water and oxygen is able to diffuse between the pavers, through the coarse base material, and into the soil.
Porous concrete and asphalt are other options and offer the option of simpler and less expensive installation costs. These materials provide a solid surface that can be shoveled and brushed just like traditional concrete and asphalt, but allow water and oxygen to easily pass through to the base and soil and roots underneath the whole system- and they look good.
Boardwalks and porous pavement aren't the answer to every problem, and they may end up costing a bit more at installation time. However, if the goal is to save the entire landscape including the trees during and after the hardscape installation, they are very good options. For more information on porous paving products, visit these three web sites: www.perviouspavement.org , www.millermicro.com/porpave.html , www.uni-groupusa.org/ .
Powdery mildew has been seen on a wide variety of woody shrubs in Minnesota this year. Infections range from a light dusting of powdery white spots to leaves completely covered with dense white felt. Ninebark (Physocarpus opulifolius; especially varieties with dark leaves), arrowwood viburnum (Viburnum dentatum), hawthorn (Crataegus spp.), and lilac (Syringa spp.) are just a few of the ornamental shrubs that have been observed with this fungal disease.
Powdery mildew is easy to recognize because it looks just like its name. Powdery white fungal mycelia and spores can be found on the surface of infected leaves, stems, flowers and fruit. If the disease starts on mature leaves, the fungus is often only a few spots or a light coating of white on an otherwise healthy looking leaf. These infections are typically considered minor infections, and have little effect on the overall health of the shrub. If the disease comes in on young developing leaves, shoots and flowers, however, leaves may be severely affected. It is not uncommon to find young leaves that are crinkled, cupped upwards or otherwise distorted by powdery mildew infections. These leaves often turn yellow or are covered in white fungal growth. Young flowers and fruit may be completely coated with the white fungus and often fall off prematurely. Young shoots that are severely infected may even be killed.
One way that the powdery mildew fungi survive Minnesota’s harsh winters is by colonizing young tissue within plant buds. In these cases the fungi starts up new infections as soon as the buds open in the spring. A shrub that has a few very severely infected young shoots next to other, completely healthy shoots, most likely had powdery mildew fungi surviving in its buds all winter long. This type of infection can be seen on many ninebark shrubs this year.
Powdery mildew fungi are favored by mild weather (60-80F) and high humidity. They thrive in shade and cause the most severe infections on young, succulent shoots. In addition, most powdery mildew fungi can only cause disease in one genera or one family of plants. The powdery mildew fungi on lilac will therefore not spread to the rose bush in the yard. A different species of powdery mildew fungi must be present to infect the rose bush.
What can be done to control these powdery pests?
First, many powdery mildew infections do not significantly harm the host plant and therefore do not need to be controlled. Many lilacs bloom beautifully year after year despite repeated infections with powdery mildew. Mature trees may have powdery mildew on the lowest leaves, but this is such a small proportion of the canopy that the tree’s overall health is not affected.
In cases where leaves and shoots are distorted, yellowed, and stunted, action should be taken. If only a few shoots are severely infected, these can be pruned off and removed from the garden. This is true for infected flower clusters as well as leafy shoots. In addition, infections on stems should be removed, since these often turn into bud infections and survive the winter in that form.
Humidity around the plant should be reduced as much as possible. Mulch around the shrub with woodchips or other organic material to keep moisture in the soil. Improve air circulation around the plant by removing any weeds crowding the plant. Place shrubs in areas of the garden where there is good air movement and sun appropriate for the shrub’s needs. Do not over fertilize shrubs suffering from powdery mildew. Fertilizer often results in a flush of new succulent growth that is easily infected by the fungus.
If all cultural control practices are not enough to control the disease, a protective fungicide can be used to control powdery mildew. Sulfur is a low impact fungicide that is effective against powdery mildew. It can burn some plants (like viburnum), so gardeners should test the spray on a few lower leaves before spraying the whole plant. Sulfur should be applied during cool evening or morning hours. For plants sensitive to sulfur or plants with severe infection on young growing shoots, the systemic fungicide thiophanate methyl can be used. If a fungicide is used, read the label completely and follow all instructions.
An interesting insect was found defoliating currants in St. Paul (Ramsey Co.) recently. The currant spanworm, Itame ribearia, is generally smooth-skinned and bright yellow with white patches, and many black spots. It is a relatively small caterpillar, growing to about 1 1/4 inch long. Like other inchworms, the currant spanworm has just two pairs of prolegs on its abdomen and makes a characteristic looping motion as it walks.
These caterpillars overwinter as eggs which hatch in spring. They feed on currants and gooseberry (Ribes spp.) from late May through June. Currant spanworms first chew the tips of the leaves down to the midrib before generally defoliating shrubs. They pupate soon after they are done feeding and emerge as moths in summer. They lay eggs on their host plants during summer, especially on the lower branches. There is just one generation a year.
A currant spanworm is generally not a common insect, but it can become abundant in localized areas. Healthy, vigorously growing shrubs should tolerate its feeding damage, although moderate to severe defoliation can reduce the attractiveness of the plant. It is too late to treat currant spanworms now, but if you had a problem this year, scout susceptible plants next spring, starting mid to late May. If you discover an infestation then, you can treat them before defoliation becomes significant. There are many insecticides that are effective, including low impact products, such as insecticidal soap, spinosad, and Bacillus thuringiensis.
With the slow spring retail season do in part to the cool weather, many retailers have a lot of plant material left (especially annuals) which they are willing to sell at discounted prices. Many of these plants are leggy and stressed from being held in small containers. A little pruning and teasing apart of pot bound roots can rejuvenate many of these plants and allow them to be great last minute additions to ones garden.
Don’t prune apples and crabapple trees this time of year. Open wounds can serve as entry points for a bacterial disease called fire blight.
Deadheading (removing spent flowers) promotes additional blooms on a number of annual and perennial flowers. Energy that would go towards fruit and seed development is available for additional growth and flowering. Annuals live for one growing season and have as their mission to reproduce before they die. Many annuals are especially responsive to producing additional flowers once deadheaded in order to produce viable seed. In addition, some perennials are also capable of having some or stronger rebloom if spent flowers are removed and include some of the perennial salvias and catmints (Nepeta spp.).
Provide tomatoes with supportive structures and consider mulch to help prevent disease. Supportive structures (cages and stakes) can help improve air circulation around foliage and discourage foliar diseases. Mulch can help retain water and prevent wide moisture extremes which can lead to fruit cracking.
Continue to water especially newly planted landscape plants as needed to help them become established. Trees can take five years or more before they become well established. When watering it is important to water sufficiently so water penetrates the depth of the root zone. For most plants it is better to water deeply and less often than shallowly and more frequent.
It is generally best to avoid the application of broadleaf weed control products and fertilizer during the hot, dry periods of summer. Avoiding summer fertilization is especially important when there is no irrigation. For perennial weeds, consider a mid-September to early October application of a broadleaf weed control product. A good time for the next fertilizer application is around the time of the state fair and into early September.
Although keeping a lawn green and actively growing during the heat of summer generally requires about 1.0 to 1.5 inches of water per week (rainfall included), if one can tolerate a little brownness to the lawn, cut back to about ¾ of an inch of water per week. This amount of water will usually keep lawns growing and generally green, but some browning can be expected. Avoid lots of wear and tear on the lawn when it is brown (dormant) and/or under severe drought stress. Lawn grasses can easily be injured or killed by high traffic levels during those periods.
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David C. Zlesak, Ph.D.