Why do dandelions all look so similar? Other plants that reseed tend to result in individuals that have noticeable differences from each other. These differences among seedlings may be dramatic or subtle and can involve traits such as flower color, petal number, or plant habit. The answer is that dandelions primarily reproduce by apomixis. Apomixis is commonly defined as asexual reproduction through seeds. The embryos are genetically the same as the mother plant and are not the result of the union of two sex cells. Most plant and animal species rely on sexual reproduction to enhance genetic variability among individuals in populations. Variability can improve the chance that at least some individuals will have a competitive advantage when disease or other challenges come. Those individuals will hopefully survive and be able to reproduce in order to perpetuate the species. Dandelions, some turf grass species, and many citrus have a different strategy that uses apomixis. The best, well-adapted individuals clone or copy themselves through seed. A relatively small proportion of embryos are the product of sexual reproduction to support variability, while most are genetic copies of the well-adapted mother plant.
Rose acacia (Robinia hispida) is in full flower across Minnesota. It is a plant many people are unfamiliar with and are asking what it is. The abundant pendulous clusters of rosey pink, pea-shaped flowers makes it especially showy this time of year. Although it is native to the Southeastern United States and is often listed as hardy to zones 5 or 6, forms of it are perfectly adapted across Minnesota and do not suffer dieback. Although not readily for sale in the garden centers, once planted (typically shared among friends) it tends to persist. The amount of it therefore continues to increase across Minnesota landscapes.
It is an easy to grow plant because of its tolerance to poor soil and drought. Often it is seen growing on old farmsteads or along the roadside. The plant habit is somewhat open and airy because of coarse stems and its compound leaves. It typically reaches 8-10 feet in height. It suckers and spreads over time into thickets, which makes appropriate placement very important. Young shoots can easily be pulled if one is persistent, but if cultivated it is best to place it in a confined area or area where it can be permitted to spread. Stands of it in Minnesota typically do not set viable seed. Because of its vigor, it is recommended not to let it escape cultivation.
Other common names for rose acacia include hairy or bristly locust. This is because the stems are covered with soft bristles. It can set multiple clusters of flowers on each stem resulting in an extended bloom time.
Rose acacia is a species of locust and is closely related to black locust (Robinia psuedoacacia). Black locust is a full-sized tree that has clusters of white, pea shaped flowers. Crosses have been made between the two species and we can periodically find the hybrids for sale in garden centers such as 'Casque Rouge' and ‘Purple Crown’. The hybrids typically grow into smaller trees than black locust and have flowers that are soft to medium pink. The hybrids have typically been selected to have limited suckering. Both locust species and the hybrids can sucker, especially when the roots have been disturbed. Because of this they tend to be used sparingly in typical landscapes.
You are invited! Come and join us for our 2nd Annual Hennepin County Master Gardeners Learning Garden Tour. We have 10 very unique gardens designed and maintained by Master Gardeners for you to enjoy. The Master Gardener homeowner and other Master Gardeners will be on site to respond to your questions. For a preview of some of some of the gardens and event please view this video.
Each garden has a different theme and demonstration. Themes include a fairytale garden, a low maintenance garden, urban and woodland retreat gardens, a farmhouse in the city, container gardening, a sanctuary garden, and a shade garden with a labyrinth. There will be practical, informative demonstrations at each site. Master Gardeners will conduct interactive demonstrations at 10, 12, and 2 p.m. on a wide range of topics. You can learn how to create small space, container, and vertical gardens, build low maintenance water gardens in a weekend, create garden rooms and rain gardens, using color to create moods, and how to grow vegetables.
Our very popular boutique will feature garden related crafts, concrete leaves and stepping stones, gardening books, and other items for sale.
All ten gardens are clustered in the Edina-South Minneapolis-and Bryn Mawr area to minimize your driving time. The intent of the tour is to provide you with an interactive and informative experience. Bring your questions! Bring your camera!
Proceeds benefit Hennepin County Master Gardener community programs.
Date: July 11, 2009
Times: 9am to 4pm, rain or shine.
Price: $15 per person when purchased prior to the event, $20 the day of the event. Tickets can be ordered onlineby clicking the "Buy Now" button on this website. Make sure you click the "Return to the U ofMN Hennepin County MG" button at the end of your order toreceive a list of garden locations and print your receipt.Or, you can stop by the HCMG office located at 479 Prairie Center Drive, Eden Prairie. Call 612.596.2130 for more information.
The price of admission includes:
With some areas of the state receiving moderate to heavy amounts of rainfall over the past couple of weeks, mushrooms are beginning to randomly appear in lawnsTheir appearance often causes people to be concerned about the health of their lawn and whether or not a serious disease might be getting started.
It’s important to remember that mushrooms are the ‘fruiting bodies’ of fungi living in the soil and thatch. They are responsible for the production of microscopic spores that in turn help propagate the fungus. The vast majority of those fungi are not associated with any lawn disease causing organisms. It’s quite common for them to appear during periods of moist conditions resulting from either natural rainfall or excessive irrigation. Again, they are not necessarily indicative of any particular lawn problem. The fungi are living on decaying organic matter in the soil and/or thatch layers. This breakdown of organic matter results in at least some of the nutrients contained in that organic matter being released back to the soil. At that point the nutrients are available for continued plant growth or used by other microorganisms. If you find the mushrooms offensive, simply knock them over with a rake and remove them from the area.
The one exception to the above situation is a lawn problem known as fairy ring. Symptoms in the lawns appear as dark green arcs and/or circles; often darker than the surrounding grass on either side of the ring or arc. There are a number of different fungal organisms associated with the production of these arcs or circles. If you suspect this problem is in your lawn please view this link on fairy rings which is part of the diagnostics feature on the University of Minnesota Extension Gardening Information website.
When trying to select the ‘right’ weed control product, consumers are often confronted with a bewildering array of possibilities at retail gardening outlets. This prompts the honest question of ‘Which one of these products should I choose?’ Likewise, this question can have a variety of responses depending on what weeds are being targeted. This could easily be the topic of several articles.
However, there is one word of caution that is worth noting. Nonselective weed killers, that is, those that will kill all green vegetation, should not be used to treat weeds in lawns and expect the lawn not to be damaged. The result will end up like pictured where all the plants that contacted the herbicide, including the lawn grasses are killed leaving small to large patches of brown dead grass. These will now need to be reseeded or resodded since none of the grasses in these areas will come back. The two most common ingredients in these types of herbicides are glyphosate (e.g., Round-up, Kleen-up, many others) and glufosinate – ammonium (e.g., Finale). These should not be used to treat weeds in lawn areas unless the desire is to kill both the existing grass and weeds such as might be done before installing a new lawn.
For more information on homeowner available herbicides and how to go about choosing an appropriate weed control product, see the article on weed control in the May 15, 2008 Yard and Garden Newsletter.
July often signals the time to be extra careful when using weed control products as lawn grasses can be injured and/or weeds not controlled very well. The reason, high temperatures accompanied by often dry conditions. This puts our lawn grasses under stress and often slows the growth of both weeds and grasses. Product label directions will usually give specific temperature ranges for when their product should and should not be used. It is important to follow those directions exactly not only because it will minimize the chances for injury to desirable lawn grasses but it’s a violation of federal law to use the product in ways that are inconsistent with its label. Also, the return of cooler temperatures and usually more rainfall later in the summer is usually a much better time to control perennial broadleaf weeds. Unless absolutely necessary, postpone control of these weeds until later in the season.
In the past, no other segment of the floriculture production industry has enjoyed public interest and use of its product more than bedding plants (annual flowering plants). Bedding plants are an indispensable item for landscape use, presenting an array of flowers and foliage that add color and texture to the landscapes of homes, apartment complexes, shopping malls, public buildings, city streets and parks.
The University of Minnesota supports this growing industry through annual flower trials conducted at Morris, St. Paul and Grand Rapids. In 2008, we evaluated annual flowers from eighteen major plant companies. Our gardens are open to the public and industry for selfguided tours throughout the growing season, providing a unique opportunity to compare performance of bedding plant cultivars under regional conditions. The public's response to the 2008display gardens at all locations was very positive. Several thousand people visited these sites during the summer. Numerous educational programs and garden tours were provided at all sites, highlighting the outstanding annuals in our trials.
The three annual flower test locations represent three very distinct climates. The St. Paul site has cool springs and hot summers and offers a good test of plants in a large metropolitan area. The Grand Rapids site has a short growing season and cool summer temperatures, and the Morris site has typically hot, dry summers with more wind than the other two sites.
Annual flower trials evaluate plant height, width, and uniformity; flower size; flower and plant quality characteristics; and disease resistance for a wide variety of annuals. Cultivars are grown from seed or are vegetatively propagated. They are planted and rated periodically for field performance. Home gardeners and commercial bedding plant producers can identify cultivars best suited for their locations from evaluations of over 400annual flowers.
All three locations have been All America Selections Display Gardens, (AAS) since 1990, and grow the AAS winners from the past five years. The AAS Award recognizes a flower or vegetable variety proven to be superior to all others on the market. An AAS Display Garden provides the public an opportunity to view the new AAS winners in an attractive, well maintained setting. Additionally, Display Gardens provide educational AAS programs during "open house" or "field day" events during the peak season for garden flowers and vegetables.
A goal of the West Central Research and Outreach Center (WCROC) in Morris is to establish a regionally recognized public research garden. The WCROC offers an aesthetically-pleasing garden where interested gardeners can learn and share ideas, and students can work and learn about plants and the environment. Recent and on-going projects support our goal of providing research and evaluation of horticulture plants in an exciting and enjoyable setting. Examples of such projects and events include:
Horticulture Night – Horticulture Night has become the WCROC's premier regional event, attracting over 1,400 visitors annually. It is held the last Thursday in July from 5:00 to 9:00 p.m. Visitors participate in walking tours of horticulture research and display gardens and enjoy special landscape and garden demonstrations. In addition to tours and displays, young and old enjoy dozens of fun, hands-on activities. Horticulture trade show vendors keep visitors updated on the latest plant materials, garden supplies, landscaping and lawn care products, equipment and available services.
Pomme de Terre Overlook – This new fifteen acre overlook connects the WCROC's agriculture, horticulture and renewable energy research with the people and natural resources of west central Minnesota. The trail system connects the existing children's garden, research and display garden, woody arboretum, and restored native prairie area with the Morris city bike / walking trail system and its largest city park. The overlook enhances the WCROC's status as a regional and statewide natural resource educational destination.
Low Input Sustainable Turfgrass Trial - The University of Minnesota Turfgrass Science Program is developing low-input turf for the Upper Midwest. We are evaluating the potential of native and non-native turfgrass species for use as turf in low and medium maintenance situations. There is a great need for more information about turfgrass mixtures in low-input management situations (reduced mowing, no irrigation, less fertilization, etc.).
We established a low-input turfgrass evaluation trial at Morris in the fall of 2007. The study examines the usefulness of 10 grass species with 3 replications of both monocultures and mixtures at various management levels. The trial is mowed monthly at a height of 3 inches during the growing season, clippings returned. No irrigation, fertilizer, or pesticides are applied. Data collection includes turfgrass quality, stand density, weed pressure, drought tolerance, vigor, diseases identified and evaporative transpiration recorded. Dr Eric Watkins from the University of Minnesota, Department of Horticultural Science, is coordinating this experiment and results will be shared after the 2009 growing season.
High Tunnel Raspberries - In 2008, we experienced our first growing season with an experimental trial of fall-bearing raspberries in our high tunnel plastic hoop house. This project is the first to experimentally assess high tunnel raspberry production in Minnesota.
Minnesota growers of horticultural crops are constrained by the short growing season and cold winter temperatures. Techniques enabling growers to extend the season for marketing later into the fall would be a significant economic benefit. Researchers have estimated between 20 to 100% loss of fruit on primocane fruiting (fall-bearing) raspberries when freezes occur before September 15th in Minnesota. Unheated high tunnels, consisting of a metal frame covered by polyethylene, have allowed horticultural producers to extend the production season of certain crops.
The primary goal of our high tunnel raspberry production research team is to minimize the impact of farming practices on human health and the environment. Eliminating fungicide and herbicide use in raspberry production and minimizing insecticide use will result in cleaner water and safer food. In addition, we aim to:
Horticulture Night- July 30, 2009 (5-9PM)
West Central Research and Outreach Gardens, State Hwy. 329, Morris, MN
Come for a fun-filled, educational evening for the whole family. There will be garden tours, demonstrations, food, vendors, and more. Please call 320-589-1711 if you have questions.
This special weekend features an information fair and water-wise demonstrations, art activities, music and a Heart of the Beast Puppet Theatre performance! Part of the 2009 Waterosity theme, this special weekend brings together additional resources and events surrounding the theme of water usage and water-wise practices. Here are just some of the special highlights:
The renowned In the Heart of the Beast Puppet and Mask Theatre will present Are You Thirsty?" (11 a.m. & 1 p.m. July 11 & 12).
Performances will be free with Arboretum admission.
Volunteers will be on hand to help showcase the various exhibits
The information fair will include several area industry and non-profit groups that are involved in water use and management.
While at the Arboretum, don’t miss all the great art displays dispersed throughout the grounds. The over a dozen special art displays celebrating Waterosity will be in place through early October. Artists far and wide submitted ideas this past year for consideration and a subset were selected for implementation. Here are just a couple highlights!
Designer: Mike Helbing, artist, Chicago, IL
Derived from the natural elegance of an unfolding fiddlehead, veins of a leaf or trees in winter, this fountain describes the peacefulness of the Arboretum woods. It reflects an attitude of working with and accepting nature while bending it to our benefit and needs. This sculpture works as an aerator to provide oxygen to the water in the pond. Its form provides aesthetic joy, and, as a tree stripped bare of leave, it also has beauty when the water is off.
Designers: Sean Jergens, Landscape Architect, ASLA, RLA; Sandra Rolph, Landscape Designer, ASLA, LOOD AP; Jenny Salita, Landscape Designer / Urban Planner, ASLA, Minneapolis, MN
Discover the ‘water stories’ of people from 12 countries, from tiny Malta to the U.S.A. Each steel column grouping shows the average daily freshwater use by one citizen of that country in a single day. Agricultural irrigation dominates freshwater use, as highlighted by the spiral planting of wheat. Consider water as a vital, valuable, shared global resource.
Watering your garden and lawn… it seems so straight forward. When the soil is dry or a plant wilts, water. If it doesn’t rain for two weeks, water. If you happen to have the hose on, sprinkle on a little water.
Not so. There are many factors – the type of soil and the amount of sun and wind in your yard, the types of plants that you grow, weather patterns, and your cultural practices – that play into a landscape’s water needs. The water-wise gardener considers and plans for these factors to produce beautiful landscapes while minimizing water use.
Study your Yard
Let’s address the soil first. Knowing your soil type – sandy, loam, clay – is the most important factor when determining how much and how often to water. Having your soil tested at the University of Minnesota Soil Test Lab (www.soils.umn.edu) is a reliable, easy, and inexpensive way to find out what kinds of soil your yard contains. On one end of the soil spectrum are sandy soils with their large particles that allow water and nutrients to drain and leach away quickly, leaving you with a low-fertility soil that dries out quickly. On the other end are clay soils with their small particle sizes packed so closely together that there is little space between particles. As a result clay soils are prone to poor drainage, low air porosity, and compaction. It is not hard to figure out why sandy and clay soils are often called “problem” soils and that sandy soils will need more frequent watering than clay soils.
Adding organic matter- compost, peat moss, composted manure - will do wonders to improve the water-holding capacity of both sandy and clay soils. Compost-amended sandy soils will do a better job of holding on to water and nutrients. In clay soils, compost will improve the arrangement of all of the small particles, increasing the air space, so that oxygen is more available to plant roots and water drainage improves. With both soil types, adding compost improves the balance of water, oxygen, and nutrients in the soils, making it easier to grow healthy plants with lower input from you the gardener. For more information on soil amending and compost please visit http://www.sustland.umn.edu/implement/amending_soils.html
The light levels in your yard – full sun, partial shade, or full shade – and your yard’s exposure to wind affects the moisture level of soils and how often you have to water plants. Sunnier and windier sites will need more frequent watering that more protected and shadier sites.
Right Plant for the Right Place
As you design your gardens and browse through your favorite garden center, remember to pick plants that will grow well in the soil types and light levels of your yard. If you want to minimize watering or have sandy soils, choose plant varieties such as sedum and low bush honeysuckle that tolerate drier conditions and require less water. Plants like turtlehead and red-twigged dogwood that prefer moist soil areas would do poorly under dry conditions.
Remember that some plants do well in full sun, others in partial or full shade. Attractive companion plantings chosen both for visual appeal and common water and light requirements will produce the healthiest and most beautiful landscapes while minimizing water requirements. For more guidelines about plant selection, visit the University’s website Sustainable Urban Landscape Information Series (SULIS) at www.sustland.umn.edu.
Water-wise Cultural Practices
It’s planting time. Spacing of plants plays a role in watering needs too. Placing plants too closely together will increase the competition between the plants for resources such as water and nutrients. Be sure to space plants based on their mature size, allowing them to grow to their full potential above and below ground to minimize plant stress.
Organic mulches – wood chips, shredded bark, pine needles, straw, grass clippings, shredded leaves - are great tools for the water-wise gardener. A three- to four-inch layer of mulch over a garden buffers soil temperatures and serves as a barrier that slows the rate of water evaporation from soil into the air. The net result is less fluctuation in soil moisture and more water available to plant roots, which improves root growth while reducing irrigation needs. In addition, as organic mulches break down, they add organic matter to soils, improving the water-holding capacity of soils.
Mulches discourage weed growth in our gardens, eliminating the competition for water between our landscape plants and weeds.
Woody plants and turfgrass don’t coexist well. We have all struggled to keep sun-loving grass varieties alive under the canopy of a tree. But with their density and close proximity to soil surfaces, turfgrass roots enjoy a competitive advantage when they cover tree and shrub roots, and siphon off vast amounts of water. This is an even bigger problem during periods of drought, creating a double dose of stress for woody plants. Replacing turf around trees and shrubs with an organic mulch eliminates all of these problems and reduces irrigation needs – no more pouring water on grass struggling to grow in shade, no more grass roots stealing water from roots of woody plants, and less evaporation of water from mulched soils around trees and shrubs. For more information on mulching, visit Mulching and Watering.
How about watering our plants efficiently to conserve water? Efficient irrigation means applying water in the proper amount, proper location, and only when it is needed.
How do you know when you should water? As a rule of thumb, water infrequently but do water before plants wilt. When you do water, give plants a deep thorough soaking. Frequent, shallow watering causes plants to produce shallow root systems that cannot survive the heat and dry conditions of mid-summer months. Watering deeply and infrequently causes plant roots to grow deeply into the soil in search of water, resulting in deeply rooted, more drought-resistant plants. Remember that sandier soils, higher temperatures and wind velocities, periods of drought, and recently-planted gardens all require increased watering.
Watering in early morning when evaporation rates are low conserves water.
Applying water at the root zone of plants either by hand or through drip irrigation is another water-wise practice. Drip irrigation is the slow application of water directly to the plant's root zone using emitters spaced along tubing lying on the ground. Water is absorbed slowly and more deeply into the soil and root zone, helping to maintain the right balance of water and air in the soil while promoting deeper root growth. No water is wasted on non-growth areas, evaporation is reduced, and runoff and wind-blown water is avoided, making drip irrigation a great water conservation practice. For more information on drip irrigation, visit Drip Irrigation for Home Gardens and Drip Irrigation Tutorial.
How efficient are automated sprinkler systems? The design of an automated sprinkler system determines its efficiency. But an efficient irrigation system can still waste water if it is programmed to run too often or too long. Initial programming and seasonal adjustments to the program of an automatic sprinkler system should be based on the type of plants you are growing and their water needs, soil type, seasonal temperatures and moisture levels, and exposure of your site to light and wind. Adjusting your sprinkler’s programming seasonally both conserves water and improves plant health by matching water applied to plants’ needs.
Rain sensors incorporated into your automated irrigation system are another water-conserving tool. Automatic rain shut-offs turn controllers off when there is sufficient rainfall. Your controller’s manual override will do the same thing, but for people often away from home, rain sensors are a great alternative. For more information on efficient irrigation and home irrigation systems, please visit Operating and Maintaining a Home Irrigation System.
The Cutting Edge is an educational display that is part of the 2009 Minnesota Landscape Arboretum’s Waterosity Educational Exhibit. The display focuses on how more water conservative lawn grasses combined with some small changes in lawn care practices can reduce water needs and other inputs going into the lawn.
The exhibit features small plots of several lower maintenance lawn grasses that are starting to see greater use in more water conservative lawns. For more information on low maintenance grasses, please visit Cool Season Grass Selection. Additionally, a plot of tall fescue, an up and coming turfgrass species with good drought tolerance and some adaptability to shady conditions, is featured. Prairie junegrass, a native of Minnesota prairies, is also be on display as it would appear in a lawn situation. As it already has very good drought tolerance, this shorter growing native species is currently involved in a rigorous U of M plant breeding program to increase other desirable lawn grass characteristics. In addition to viewing separate species and varieties of lawn grasses, both a no-mow mix and an ecology lawn mix are on display to provide yet another alternative to a traditionally managed lawn. For more information on turfgrass research at the University of Minnesota please visit Turfgrass Science and click on the research tab.
Cultural practices play a very important role in determining water needs of lawn grasses. For example, the practice of raising mowing heights will encourage deeper rooting, thereby providing greater access to soil moisture reserves. Shorter mowing heights restrict rooting depth and make lawn grasses more dependent on us to meet all of their water needs. For additional information on mowing please visit Mowing Practices.
There will be special displays in the Cutting Edge regarding a variety of different watering practices and products. Information and displays on the use of mulches in landscape beds and gardens to help conserve soil moisture, reduce weeds and lower soil temperatures will be featured. Smart watering accessories like timers and automated control systems will be on display. Something as simple as a timer positioned between the garden hose and the outdoor faucet provides better control over how long watering will occur. In automated systems, soil moisture sensors can tell the system when the soil is wet enough and doesn’t need any more water and will also shut the system off when it’s raining.
The Cutting Edge display provides many ideas that homeowners can adopt to conserve water in the managing of their lawns and other landscape areas. Folks are invited to come observe and interact with the various elements of the Cutting Edge.
In-depth information on watering lawns can be found at Sustainable Lawncare Information Series' Watering Practices.
Do you live in a geographic area with little rainfall? Do your sandy soils allow water to percolate away quickly? Are you looking for a drought-resistant landscape? Are attractive landscapes and water conservation both goals of yours? Below is a partial list of trees, shrubs, and herbaceous perennials that once established, grow well with little supplemental watering. Within most of the species listed, there are cultivar choices that will provide you with a wide variety of ornamental traits.
|Common Name||Scientific Name||Exposure*|
|Autumn Gold Ginkgo||Ginkgo biloba||‘Autumn Gold’S|
|Black Walnut||Juglans nigra||S|
|Blue Beech||Carpinus caroliniana||S/Psh/Sh|
|Bur Oak||Quercus macrocarpa||S|
|Cockspur hawthorn||Crataegus crus-galli||S|
|Dakota Pinnacle® Birch||Betula platyphylla ‘Fargo’||S|
|Japanese Tree Lilac||Syringa reticulata||S|
|Kentucky Coffeetree||Gymnocladus dioica||S|
|MN Strain Redbud||Cercis canadensis||S/Psh|
|Northern Catalpa||Catalpa speciosa||S/Psh|
|Summertime™ Maackia||Maackia amurensis ‘Summertime’||S|
|Thornless Honeylocust||Gleditsia triancanthos var. inermis||S|
|Common Name||Scientific Name||Exposure*|
|Black Chokeberry||Aronia melanocarpa||S/Psh|
|Bush Honeysuckle||Diervilla spp.||S/Psh|
|Common Ninebark||Physocarpus opulifolius||S|
|Gray Dogwood||Cornus racemosa||S/Psh|
|Gro-Low Fragrant Sumac||Rhus aromatica ‘Gro-Low’||S|
|Hedge Cotoneaster||Cotoneaster lucidus||S|
|Japanese Barberry||Berberis thunbergii||S|
|Korean Barberry||Berberis koreana||S|
|Nannyberry Viburnum||Viburnum lentago||S/Psh/Sh|
|Rugosa Rose||Rosa rugosa||S|
|Tiger Eyes® Sumac||Rhus typhina ‘Bailtiger’||S|
Evergreen Trees & Shrubs
|Common Name||Scientific Name||Exposure*|
|Austrian Pine||Pinus nigra||S|
|Chinese Juniper||Juniperus chinensis||S|
|Common Juniper||Juniperus communis||S|
|Creeping Juniper||Juniperus horizontalis||S|
|Eastern Red Cedar||Juniperus virginiana||S|
|Eastern White Pine||Pinus strobus||S|
|Jack Pine||Pinus banksiana||S|
|Red Pine||Pinus resinosa||S|
|Savin Juniper||Juniperus sabina||S|
|Swiss Stone Pine||Pinus cembra||S|
|White Spruce||Picea glauca||S/Psh|
|Common Name||Scientific Name||Exposure*|
|Black-eyed Susan||Rudbeckia hirta||S|
|Butterfly weed||Asclepias tuberosa||S|
|Catmint||Nepeta x faassenii||S|
|False Blue Indigo||Baptisia australis||S/Psh|
|Globe Thistle||Echinops ritro||S|
|Lamb’s Ears||Stachys byzantina||S/Psh|
|Little Bluestem||Schizachryium scoparium||S|
|Russian Sage||Perovskia atriplicifolia||S|
|Prairie Dropseed||Sporobolus heterolepsis||S|
* S=Sun Psh= Part shade Sh=Full shade
For most areas of Minnesota, the spring of 2009 has been an unusually dry one. This cool dry weather has kept many of the spring leaf spot diseases of trees at bay. Diseases like anthracnose on oak, ash and maple have been absent up until the most recent wet weather. Anthracnose is now being reported, especially in areas that received significant recent rain like southern Minnesota. The fungi that cause anthracnose, however, may not be causing problems for long. Anthracnose fungi thrive in cool wet weather and with the recent onset of hot temperatures, the growth and spread of this disease is likely to slow down.
The biology of these fungal leaf diseases explains why in some years anthracnose is a big problem and in other years only minor damage occurs. Anthracnose fungi survive Minnesota’s winter in infections on twigs, buds, and last year’s infected leaves. Spring rains splash spores from these infections onto newly developing leaves. These spores cause irregular brown leaf spots often centered on leaf veins. Since the infections occur on young developing leaves, it is common to see curling or distortion of the leaf tissue as parts of the leaf continue to grow, while others are halted by the anthracnose infection. If severe infection occurs, leaves may drop off the tree prematurely.
If cool wet weather occurs throughout spring months, the anthracnose fungi thrive and disease can be quite severe. This year, wet weather did not arrive until late spring. Some anthracnose is occurring on oak and ash trees, but the leaf spots are fairly minor and mostly restricted to a few lower shaded leaves. In contrast, more significant leaf browning has been noticed in maples.
Oak anthracnose is caused by the fungi, Discula quercina. Ash anthracnose is caused by the fungi Discula fraxinea. Both of these fungi primarily infect young developing leaves or wounded leaves. Once oak and ash leaves reach maturity, they are relatively resistant to the fungi. It is likely that less disease is being reported on these two trees because the wet weather that favors these fungi did not occur until the majority of the leaves were fully expanded and therefore somewhat resistant. For plant disease to occur, the pathogen, the susceptible host plant and the right weather conditions must all occur at the same time or disease will not develop.
There are several different fungi that cause anthracnose in maple including Discula umbrinella, Discula campestris and Aureobasidium apocryptum. Less is known about the biology of these fungi. They result in similar browning and curling of leaves and can even blight young shoots. Like oak anthracnose and ash anthracnose new infections often form in response to wet weather. Unlike anthracnose on oak anthracnose and ash anthracnose, the fungi that cause maple anthracnose have been reported starting new disease from late spring through late summer. Anthracnose on maple seems to be the most common of the three diseases this spring.
Although a tree heavily infected with anthracnose can appear ratty, this disease is not a serious threat to the health of the tree. Often leaf spots are limited to the lower shaded leaves. The majority of the tree’s canopy remains green and can provide energy to the tree through photosynthesis all summer long. Even in years when anthracnose is severe and leaf loss occurs, trees create a new flush of leaves early enough in the year to avoid serious harm.
All species of willow, most poplar (but rarely quaking aspen), and occasionally birch and alder are susceptible to attack by the poplar and willow borer, Cryptorhynchus lapathi. This insect, a type of weevil, is 5/16 - 3/8 inch long with a slender snout as long as its head. It has a roughly textured black body with mottled cream to tan colored patches on its body and its legs, including the back 1/4 of its wing covers.
Poplar and willow borers overwinter as larvae in small cavities they excavate under the bark. The larvae continue feeding in the spring, expelling frass (a mixture of sawdust and excrement) out of openings as they tunnel around stems or branches. They eventually pupate in June and then emerge as adults in late July or August. Adults feed on young stems, laying eggs in slits in the bark. The larvae tunnel under the bark, creating galleries in all directions. They chew exit holes in order to push the frass out.
These borers commonly attack trees between 1 - 4 inches in diameter and are particularly common on the lower trunk, especially near the root collar. Their tunneling can result in irregular splits, cracks, and dead patches on the bark and around exit holes. Stems can become deformed and some trees may become bushy due to epicormic sprouting. Extensive tunneling can cause small stems or branches to die or break. Damage is most severe on newly planted trees and nursery stock.
Management can be challenging. Remove and destroy infested stems. This is most effective if there is not a lot of susceptible trees in the area and poplar and willow borer populations are relatively low. You may be able to kill or remove larvae in their tunnels by poking a wire into holes (the larvae are active in the tunnels where the frass is being expelled). Another option is to treat trees with a residual insecticide, such as permethrin, when adults are first active during late summer.
A spinach leafminer, Pegomya hyoscyami, is a small anthomyiid fly whose larvae attack the leaves of spinach, beets, chard, lambsquarter, and other plants. This fly overwinters as pupae and the adults emerge the following April and May. The adult is hairy, about 1/4 inch long, and grayish or brownish. It lays eggs on the underside of older leaves. A spinach leafminer larva hatches into a carrot-shaped, whitish maggot that lacks legs or an obvious head.
The larvae tunnel into leaves, between the two leaf surfaces. The mines are long and narrow at first, but eventually become an irregularly shaped blotch area. These mines are opaque initially and then later turn brown. The larvae are active for about two to three weeks before dropping to the ground and pupating. Several generations can occur during one year. This activity has little impact on plant growth but can be quite destructive to vegetables grown for edible greens.
Home gardeners can ignore spinach leafminer damage when it is on beets as the feeding injury does not really impact the root crop. However, when spinach leafminer attacks spinach or other leafy green crops, you should take some action to protect them. Remove weeds, like lambsquarter, that spinach leafminers may attack, to reduce their available food source. You can erect a floating row cover, i.e. fine meshed netting, cheese cloth or some similar material that allows sunlight and rain in but prevents insects from getting to your plants. This should be done in plots where you have not had spinach leafminer problems for at least one year as overwintering pupae near susceptible plants can produce adults under the barrier which can still infest plants. Remove and destroy infested leafs when mines are small.
You can apply a garden insecticide, such as permethrin, in the spring when adult flies are first active. Double check that the insecticide you want to use has the vegetable, e.g. spinach, you intend to treat on the label. Make sure you get good coverage on the leaves. For the best protection, make several treatments at regular intervals (check the label to determine how often you can apply the product you are using). Be sure you observe the number of days from the last treatment to when you can safely harvest your crop.
With the discovery of emerald ash borer (EAB) in St. Paul in May, many people have been asking for information on how to protect their ash with insecticides. While there are several options available to home residents within 15 miles of the infestation, the question people should be asking now is when should I treat my ash. In general insecticide applications should be made from early May until early to mid-June. With that in mind, it is really getting late to be treating your ash any longer this summer.
It is possible that Tree-age (emamectin benzoate), which is a professional use only product, can be applied into July because its mode of action targets the larvae and not the adults. However imidacloprid relies on being taken up by the tree into the canopy and killing adults that feed on leaves. Because it takes three to four weeks for imidacloprid to be translocated in trees, any applications that take place now, will have little impact in protecting ash. This is particularly true for products available to the general public. If you are thinking of treating your ash yourself now, don’t do it. You will be just wasting insecticides. The next window of opportunity for insecticide applications will be this fall or next spring.
There are many factors to consider if you are thinking about treating your ash for EAB. For more information on insecticide options for protecting ash from emerald ash borers, please see the EAB Insecticide Fact Sheet (pdf).
Recent rains throughout much of Minnesota have been much needed after the dry spring. Continue to water plants as needed. There are a lot of great tips on watering in the Water-Wise Gardening article in this issue. Plants to especially pay close attention to for supplemental water include those growing in containers and those that have been recently planted and are still in the process of adapting to their new site and establishing a well-developed root system.
Raspberries are coming into fruit! Raspberries produce canes that last for two growing seasons. The first year canes start from the base of the plant and are called primocanes. These primocanes overwinter and flower and fruit on side buds during the second growing season. During the second the canes are called floricanes. There are some raspberries on the market called primocane fruiting. These raspberries produce primocanes that begin flowering and fruiting the fall of the first growing season after a predetermined number of leaves are produced. If left to overwinter, these primocanes that began fruiting at their tips can continue to flower and fruit on additional side buds down the cane. After second year canes have finished fruiting later this month, prune them to the ground in order to direct more energy and room to the current season’s primocanes.
Faithful removal of spent flowers of many annuals and some perennials will help them continue to flower strongly. Examples include geraniums, zinnias, dianthus, and catmint. Plants produce flowers in order to make seeds and reproduce. If the hormonal signal of developing embryos is removed by deadheading, many plants will respond by producing additional flowers.
Enjoy the garden! July is typically a month of bounty. More vegetables are ripening, trees and shrubs are fully leafed out, and there are many flowers in bloom. During our time in the garden we may notice a small problem starting. If we catch it early we have the opportunity to be proactive and intervene. For instance, small weeds can be removed before they become larger, more difficult weeds to remove. Additionally, when we notice disease or insect problem starting, we have a better chance to intervene and prevent significant spread and damage. Please visit the diagnostics modules on the gardening information website (www.extension.umn.edu/gardeninfo) for help in identifying pest problems and to learn about control options for the particular pest. These modules will continue to expand and include more resources as time goes by.
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David C. Zlesak, Ph.D.