|
|
For many gardeners magnolias conjure up an association with the South. Movies such as "Steel Magnolias" reinforce this connection, and the glorious purple/pink blushed white flowers of the large-flowered saucer magnolia, common in the South, is the magnolia most familiar to the general public. The most widely grown magnolia with reliable performance in Minnesota is the star magnolia (Magnolia stellata). Star magnolias are typically grown as large shrubs, but can also be trained into a small tree. They are covered with white or blush white 3 inch blooms typically just before the crabapples come into flower. Star magnolia blooms emerge before the foliage, making their floral displays seem even more impressive in the spring landscape. Fortunately, the star magnolia is just one of many magnolias that are proving themselves as reliably hardy in Minnesota. Another magnolia to consider is the bold and exotic-looking umbrella magnolia (M. tripetala).
The umbrella magnolia is a medium sized single or multi-stemmed tree that typically grows 20-30 feet tall. Its thick, stout stems and infrequent branching gives it a coarse look, somewhat reminiscent of the architecture of a Kentucky coffeetree (Gymnocladus dioicus). The exceptionally large foliage of umbrella magnolia gives it its common name. Foliage is 1 to 2 feet in length, elongated, and slightly diamond shaped. Leaves are closely spaced and typically radiate symmetrically on the current season’s flowering stems. Vigorous, faster growing stems are also produced with leaves more distantly spaced. In late May and June huge blooms with creamy-white petals about 6 inches in length are produced. The nicely scented flowers are typically borne singly at the ends of the current season’s growth after several leaves have expanded.
The umbrella magnolia is native to the southeastern United States and is found from Florida to New York and west to eastern Oklahoma. It is often touted as being hardy to USDA cold hardiness zone 5, but there are many large specimens in Minnesota that have not experienced dieback. Trees greater than ten years old can be seen at the University of Minnesota Landscape Arboretum and the University of Minnesota St. Paul campus. Umbrella magnolia is sold by some Minnesota nurseries. Because cold hardiness is likely variable within the species and depends on the seed source, purchase plants propagated from more northerly, cold hardy stock. As the popularity of this plant grows, perhaps there will be a cold hardy strain specifically marketed, much like the Minnesota Strain of eastern redbud (Cercis canadensis).
Umbrella magnolia does best in a partially shaded location with a rich, moist soil that is well drained. Locations near larger trees or buildings that offer protection from excessive wind will help keep the large foliage from being damaged. If you are looking for a bold medium-sized tree for your landscape that will be sure to become a conversation piece, the umbrella magnolia may be just the tree for you!
A Hardy Plant Research Symposium will be held Thursday June 19, 2008 (8:30AM - 5:30PM) at the University of Minnesota Landscape Arboretum to celebrate the history, present, and future of hardy plant introductions. This event helps to commemorate the 100th anniversary of the Horticultural Research Center and the 50th anniversary of the University of Minnesota Landscape Arboretum. University of Minnesota researchers will be joined by distinguished guests from the National Arboretum in Washington, DC, the University of Connecticut, and South Dakota State University to present the program.
Topics include:
Following the seminars there will be tours of the Horticultural Research Center, the home of the University of Minnesota apple and grape breeding programs and more and also several of the collections within the Minnesota Landscape Arboretum. The evening will wrap up with a Minnesota wine and cheese reception and displays highlighting research projects to view. The schedule and registration is available online http://www.arboretum.umn.edu/UserFiles/File/HardyPlantResearchSymposium.pdf . Due to the limited time from this newsletter coming out and the event, please call 952-443-1422 to reserve your spot. Students attend for free and there is a $25 fee for nonstudents. The cost includes symposium presentations, refreshments, lunch, tours, and proceedings.
Aliens have Landed
The frequent rains and cool weather this spring have created excellent conditions for Cedar Apple Rust and Hawthorn Rust galls on species of Juniperus, including junipers and red cedar (Juniperus virginiana) trees. These fungal galls produce bright orange gelatinous spore producing tentacles, called telial horns, when wet. The galls themselves are small round brown woody balls that easily go unnoticed. When the wet weather arrives however, the show begins. Bright orange telial horns can swell, dry down, and swell up again multiple times in the spring in response to frequent rain events. Each time the orange telial horns swell, spores are released and are carried by wind currents to infect susceptible apple, crabapple or hawthorn trees. When the galls are finally spent, the telial horns fade away, and the gall dies and often falls off the tree within a year. Little to no damage is done to the red cedar or juniper tree as a result of this colorful infection. No control strategies are necessary; simply enjoy nature’s unique tree ornamentation.
Anthracnose in Trees
Anthracnose is a leaf disease of shade trees that commonly occurs in cool wet spring weather. There are several different anthracnose fungi. Each attacks a specific type of tree. For example, the fungus Discula quercina causes anthracnose in oak trees, and D. fraxinea causes anthracnose in ash trees. The anthracnose fungi need cool moist weather to start an infection. In addition, these fungi attack primarily young growing leaves. Once tree leaves fully mature, they are relatively resistant to the disease. Infected leaves will have brown irregular shaped spots and may be curled or distorted. In severe cases infected leaves may fall off the tree resulting in partial or complete defoliation. To date, anthracnose is not severe in the twin cities metro area. Many leaves have matured already and will resist the disease. If cool wet conditions continue, however, we may see more anthracnose developing on new leaves of shade trees.
Mushrooms Emerging
With moisture, come mushrooms. Across the state mushrooms are popping up in gardens and lawns. The majority of mushrooms are not disease causing fungi. They are feeding on organic mulch like woodchips and dead leaves, or on buried organic matter. These mushrooms will dry up and disappear with warmer drier weather. Alternatively, they can be collected into a trash bag and removed from the yard if desired. Some mushrooms can be poisonous if eaten. If small children play in the area, it might be wise to remove the mushrooms.
Mushrooms, shelf fungi or other fungal structures developing on tree trunks are a greater cause for concern. These fungi are likely to be heart rotting fungi that degrade the inner heartwood of the tree. Trees can survive many years with a heart rotting fungi, because the heartwood cells are not living, but are only there for structural support. If internal rot is severe however the tree could be at risk of breaking in a storm. The USDA Forest Service recommends that action be taken if a tree has signs of a heart rotting fungi and…
Starting Seeds in Wet Soils
Cold wet soils can favor damping off and rot of seeds and newly planted seedlings, especially in vegetables like cucumbers, squash, and sweet corn. To avoid these problems, improve the drainage of the soil by avoiding low lying areas, planting on raised beds, and redirecting runoff from downspouts and other areas to avoid the garden. Carefully watch beds that have already been seeded. If plants do not emerge close to the expected time (this is often listed on the seed packet), certain plants may need to be reseeded once the soil dries. In areas of the state experiencing flooding or continuously saturated soils, it may be wise to start a few backup plants indoors where soil moisture can be regulated.
Two flies have greeted us if we have spent much time outside, mosquitoes and black flies. Mosquitoes typically bite us during the morning and evening, although they will take a blood meal from us during the day if we are close enough to their resting sites around brushy areas, shrubs, and trees. The stout, humpbacked black flies (often called gnats) usually bite us during the day, especially during early morning and in early evening. In addition to the annoyance of bites, mosquitoes are potential vectors of disease to people, e.g. west Nile virus. Fortunately black flies are not known to transmit diseases to people in Minnesota.
It is challenging to completely avoid mosquito and black fly bites but there are few tips to minimize your exposure to them. First avoid, when possible, the times when mosquitoes and black flies are most common. When you are out, wear protective clothes to cover bare skin including sleeves shirts, long pants, socks and shoes, and hats. Wearing something on top is particularly useful for black flies as they love to bite around the hairline on your head.
The use of insect repellents, such as those with DEET (N,N diethyl m toluamide) are useful in protecting one from mosquitoes. Repellents are not consistently effective against black flies, but their use is still probably better than nothing. For more information on repellents, see the June 1, 2005 Yard and Garden Newsletter.
Soon, we will no longer be seeing wood ticks (also called American dog ticks). It wasn’t that long ago when you couldn’t go outdoors, especially around grassy, weedy areas without attracting a horde of them. So where do they go? Knowing their life cycle explains why you see them in the spring but not in the summer. Wood ticks take two years to complete their development. Eggs are laid in early summer which hatch into larvae. These immature ticks do not feed until the following spring when they turn into nymphs. One rarely encounters either immature stage. After feeding a second time, the nymphs develop into adults during late summer of the second year. The adults do not feed until the following spring when the weather turns warm. Adults are common April through June but die after laying eggs, thus completing their life cycle.
However, while wood tick problems are almost behind us, we should still be aware of blacklegged ticks (formerly called deer ticks) which are present throughout the spring, summer and fall. They have a similar life cycle - they also take two years to finish their development. However, while essentially just adult wood ticks bite us, both adults and nymphal blacklegged ticks will take a blood meal from people. This is very important because blacklegged ticks vector several diseases, especially Lyme disease while wood ticks do not transmit disease in Minnesota.
To protect yourself from ticks when you are in known tick areas, wear protective clothes like long pants and long-sleeved shirts, whenever possible use a repellent, e.g. DEET, and check yourself for ticks when you return. Blacklegged ticks need to be actually biting and then need to be attached for at least 24 - 72 hours before they can transmit any disease. If you pull a blacklegged tick off of you shortly after you have been outdoors for a few hours, it is very unlikely it has given you any disease. If you ever experience suspicious symptoms, see your physician as soon as possible.
This has been a favorable spring for slugs as they prefer cool, moist environments. To manage slugs in your garden, it is important to use multiple tactics. First, be sure any unnecessary debris, like plant debris or boards are removed as they serve as hiding places for slugs. Although we have had plenty of rain so far, if it becomes dry and you need to water, any methods that reduces humidity in your gardens helps to deter slugs. Use soaker hoses or if using overhead sprinklers, irrigate in the morning. Try to water deeply and allow more time between irrigations. When possible, stake up plants and prune lower leaves to reduce possible cover for slugs and allow better air circulation, as well as thin or divide crowded plants.
Physical removal is effective. Place newspapers or flat boards in your garden and check under them in the morning and remove any slugs you find. You can also use traps baited with beer or warm water and yeast. You can buy commercially available traps or make your own by sinking a jar or pan into the ground so the top of the container is even with the top of the ground. Be sure to check your traps regularly and clean them out when they get full and replace the attractant as needed.
Diatomaceous earth can be a reasonably effective barrier as it scratches the cuticle (skin) of slugs and causing them to dry out but controls slugs poorly when it gets wet. Wood ash can keep slugs away from plants but is usually not recommended because it raises the pH of most Minnesota soil too high, inhibiting the uptake of some nutrients. The use of egg shells around plants, although a popular home remedy, does not deter slugs.
There are a couple of pesticides that you can apply around plants to protect them from slugs. Metaldehyde is common active ingredient to control slugs. Only use this product around flowers and ornamental plants - it is not labeled for use around edible crops. It works best during warm and dry weather and less so during cool, wet weather. Metaldehyde is potentially dangerous to dogs. Another effective active ingredient is iron phosphate. You can use this product around vegetables and fruits and it doesn’t harm dogs.
MN Statute 216D, the “Call Before You Dig Law” in Minnesota, was mandated into existence by Governor Rudy Perpich and the Minnesota Legislature in 1987, as a result of escalating underground utility damages and even fatalities caused by excavations, both professional & casual alike. Gopher State One Call opened its doors in 1988 in the City of Mendota Heights, and has served all excavators in Minnesota since. GSOC has, in fact, become a national role model for success in utility damage prevention. In the past 20 years, technology & communications have evolved to the point where contacting GSOC has never been easier. With access to the internet, excavators in Minnesota can contact the “notification center for excavation” anytime.
ITIC, originally introduced in early 2004 for professional excavators, is an acronym for “internet ticketing.” It’s a method for all Minnesota excavators to “connect” with GSOC and enter their locate requests, anytime, 24 hours a day, 7 days a week! All, meaning any excavator who digs professionally or casually, and who has internet access. Facility operators (public utilities) and professional excavators currently have two ITIC options: ITIC-with-mapping and ITIC in a “Text-Only” version. They differ in that the “mapping” version requires a short training class. Attendees are taught how to draw an electronic “polygon” around their “dig” site. Upon releasing the ticket, their GSOC ticket number and a list of potentially affected underground operators and contact phone numbers appear. The “Text” version requires no training class, as GSOC customer service representatives “map” the area for the excavator. For professional excavators, all GSOC tickets are currently available on-line, including Boundary Survey and Design tickets.
Help for the homeowner
GSOC has one of the highest levels of participation in damage prevention found anywhere in the country among homeowners and casual excavators. During the busy season, calls to the center from homeowners and casual excavators may at times exceed those from professional excavators. We had to ask ourselves if there was a way to improve the experience for this calling group while making it better for all other callers at the same time. We developed a couple of alternative ways which are described in the following. Hopefully, they will help reduce homeowner ticket processing times which in turn should help reduce hold times for all.
ITIC – Not just for professional excavators, either
ITIC has been so popular that on April 17th 2006, a special version of it called “ITIC Lite” went on-line to allow homeowners to enter their own locate requests. It is very easy to use and designed specifically with the homeowner and casual user in mind.
Because there is no training required to use ITIC Lite, users have no access to mapping and will not receive a ticket number until the completed ticket is emailed back to the user. ITIC Lite is designed for “one-time” use, so no pre-registration is required. A user can access ITIC Lite at www.gopherstateonecall.com and request that an access link be sent to an email address the user designates.
Once a homeowner has completed the caller and dig-site information, the request is transmitted to GSOC via the internet. GSOC staff then maps the area utilizing the information provided by the user. Once the affected facility operators are identified by the call center computer, the ticket is automatically transmitted to them. A copy of the completed locate request is then sent to the homeowner, and GSOC files the request in its data base.
Homeowners get dedicated attention
At the same time ITIC Lite was introduced, a new ticket format, dedicated specifically to the needs of homeowners, was also rolled out. In an effort to improve the experience the homeowner has with GSOC, several questions that didn’t apply or were redundant for homeowners were removed. This, in turn, should shorten “hold times” for homeowners and/or one time callers during the busier portion of the excavation season, which, in Minnesota, historically runs from the beginning of April to the end of October.
Not only is phone time virtually eliminated, thus saving time and money, but all forms of ITIC are free to excavators in Minnesota. From April through September 2008, the traditional “busy” excavation season, ITIC and ITIC Lite users are automatically entered into a sweepstakes. One winner is chosen each month in a random drawing. Homeowners are eligible for a $250 cash prize! For more information go the GSOC website: www.gopherstateonecall.org
“Going into the red” can be scary as we think about our finances, but for color in the landscape it can be great. Shrubs with rich red, maroon, purple, or burgundy foliage provide rich accents in our landscapes, even if they do not produce showy blooms. What gives such shrubs their rich red to purple color are pigments called anthocyanins. They are especially pronounced in the fall in the plants that color up red or purple. They serve to protect the plant from ultra violet light damage as chlorophyll levels decline and plants dismantle molecules and reabsorb nutrients before dropping their leaves. Many of the shrubs grown for their season long red or purple color are not typical for their species, but are variants or mutants with elevated levels of anthocyanins of normally green-leaved species. Some plants have only red new growth to protect tender developing tissue, which later turns green like Spirea x bumalda 'Goldflame'. The combination of the red anthocyanin pigments and the green pigmentation of chlorophyll allow the foliage of many red or purple leaved shrubs to appear especially dark and sometimes even almost black.
No matter the reason why some shrubs appear red, these shrubs can be especially useful in the landscape to add a bold display of color. Astute designers often pair them with plants that have pink or mauve colored flowers to develop an analgous color theme (colors near each other on the color wheel) or golden flowers or foliaged plants for a complementary color theme (opposite sides of the color wheel).
There has been an explosion in red foliaged shrub choices in recent years, expanding the selection from the few red leaved staples serving Minnesota gardeners for decades (primarily purple leaved sand cherry (Prunus x cistena) and red leaved barberry selections (Berberis thunbergii)).
Time tested red foliaged staples
Purple leaved sand cherry (Prunus x cistena) is a medium to large sized ornamental shrub growing typically to about 8 feet if left unpruned. It is a cross of an Asian (P. cerasifera 'atropurpurea') and North American (P. pumila) species. Early spring foliage is a glowing red that as the summer progresses turns a deep, dark purple. Blush-pink flowers are borne in May and contrast dramatically with the red foliage. Fruit are seldom seen. Considerable pruning is required to obtain a dense, full plant habit. As time goes by there is often erratic stem or tip dieback and stems that droop due to their weight, both of which can lead to asymmetry and an awkward plant form when left unattended. Susceptibility to cankers, borers and other pests often limit the landscape value and lifespan of this plant.
Several red leaved barberry (Berberis thungergii var. atropurpurea) selections are available and differ based on overall plant size and foliage features. There is the larger red leafed form (standard ‘atropurpurea’) that typically grows 4-6 feet in height common in the trade and many smaller selections. Some of the smaller forms include ‘Crimson Pigmy’, ‘Rosy Glow’ (pink and dark red variegated foliage), and ‘Gold Ring’ (purple leaves with a gold edge). Barberry does well in partial to full sun and a neutral to slightly acidic soil with good drainage. Barberry typically have few pests and form a dense, full plant. Minimal pruning of stems experiencing dieback is typically needed in the spring. Its greatest liability is its sharp spines, limiting its use near walkways and where children play.
One of the most popular of the recent shrubs with red/purple foliaged selections is ninebark (Physocarpus opulifolius). Diabolo® led the way as the first widely-distributed purple leaved selection in the 1990’s. It has been used as a parent of the more recent purple leaved selections including Summer Wine™, Lady in Red™, Coppertina™, and Center Glow™. Summer Wine™ has smaller foliage and a fuller plant habit than Diabolo® and reaches about 5 to 6 feet in height at maturity. Coppertina™ and Center Glow™ are similar to each other in that they are crosses of Diabolo® with a golden leaved form of ninebark and also grow to 5-6 feet in height. They produce new growth that is golden and then as the foliage matures it becomes increasingly purple. Compared to purple leaved sand cherry, these ninebark grow to a similar or slightly smaller size and are typically longer lived and have a denser plant habit. Ninebark also has a nice spring floral display. Plant ninebark in partial to full sun in moist, yet well draining soil. Ninebark gets its name for the older stems producing attractive, multiple layered bark that peels.
There are many purple leaved forms of weigela that have come on the market in recent years. More time and testing are needed to ascertain which have enough hardiness to be reliable performers in Minnesota. In some landscape situations some have experienced considerable dieback. Some of these introductions include Wine & Roses®, Midnight Wine™, and Fine Wine™. Weigelas have long, tubular showy blooms over a long period in summer. They prefer full sun to partial shade and moist, well draining soil. Most of these purple leaved selections are relatively compact growing from a couple to few feet in height.
Purple leaved selections of elderberry (Sambucus nigra) are increasing in popularity and availability. Two of the most common ones in the trade now are Black Beauty™ and Black Lace™. They have clusters of pinkish-white blooms in the spring and grow into plants with long arching canes, typical of our native elderberry. They can be left to grow to be 8 feet or more, or pruned each spring to the ground and allowed to regrow to generate a fuller, more compact plant. Black Lace™ has more finely cut foliage than Black Beauty™.
There are many cultivars of purple smokebush (Cotinus coggygria and hybrids with C. obovatus). ‘Nordine’ is a cultivar with a reputation of being one of the more hardier forms. Smokebush in our climate typically experiences significant cane dieback, but routinely regrows vigorously from the base each season and reaches a few feet or more in height by fall. Smokebush prefers full sun and is tolerant to a wide range of soil types.
The red leaved rose (Rosa glauca; aka R. rubrifolia) has been a hardy staple to the Minnesota landscape for decades, but often has limited availability in the trade being found sporadically typically at only the higher end, independent garden centers. It is more shade tolerant than other roses (needs 4 hours or preferably more of sun a day) and is very cold hardy and does not need covering. The blue-green foliage has red highlights to it, especially in the spring and red to purple colored canes. Single pink flowers with a white petal base are produced in the spring and an abundant crop of orange-red hips (fruit) grace the plant in the fall.
Other red or purple leaved plants to keep an eye out for are both of the contorted (twisted stems) and standard forms of red leaved hazelnuts (Corylus ssp.), Sargent viburnum 'Onondaga' (foliage emerges purple and then turns green), and some of the hardier forms of red leaved Japanese maple. May our finances stay in the black, but our landscapes see a little red!
For larger views of most images, just click on the image.
Back issues Yard & Garden Line News for the past nine years are online.
For plant and insect questions, visit Ask a Master Gardener. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.
Receive an e-mail reminder when the next issue of the Yard and Garden News is posted to the web:
Happy gardening!David C. Zlesak, Ph.D.
Editor
Extension Educator