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David ZlesakDuring petal development of some roses there comes a critical point in time where cells undergo a significant milestone. Some cells have genes turned on that result in anthocynanin (a group of pigments that generally appear red, pink, or purple) production, while other cells have this pathway blocked leading to no or limited anthocyanin production. As the cells present during this milestone event continue to multiply to form petal tissue, all the subsequent tissue derived each cell should share that cell's ability to either produce or not produce antocyanin pigment. If this milestone occurs in a cultivar later in development (like in University of Minnesota breeding selection Rosa 120 on the left and many of Dr. Griffith Buck’s cultivars including ‘Spanish Rhapsody’, ‘Freckles’, and ‘Dorcas’) there will be many small regions of darker color typically called stipples. If the milestone occurs early in development, it results in larger regions of divergent color (like in Rosa mundi on the right) which are typically called stripes. Dark stripes or stipples particularly contrast well on petals having a white or yellow background.
Nymphaea ‘Bagdad’ - Tropical day-flowering water lily. Jonathon HensleyWith 2008’s gardening season fleeting, thoughts of autumn harvests, dormant winter gardens, and desperately needed pruning chores begin to settle in every Minnesota gardener’s mind. It is also a great time to qualify this year’s growing season and reflect on questions of ones gardening progress and successes. What set your garden apart in 2008? What particular accomplishments are you especially proud of? What varieties performed well for you? What is your garden lacking?
New ideas for creativity and progress in a seasonal home garden can be difficult to point at with much precision. One idea, however, has consistently shown great merit over the years for infusing gardens with new energy. Diversifying the plant groups in your garden can lead to new, fresh, and rewarding ideas. For instance, working with a new plant group, like aquatic lilies, this upcoming season can create a refreshing sense of progress and creativity in your 2009 garden. If new to you, unfamiliar aquatic propagation and cultivation techniques can provide that needed sense of development and accomplishment.
Water lilies have become the rage in recent seasons for America’s most adventurous at-home gardeners. Arresting displays, including hardy, pond’s edge plantings and container submerged day and night flowering tropicals can be found at botanical centers across the country in increasing number. Ornamental water lily displays, however, were not always commonplace in the U.S. In fact, the development and progression of most ornamental aquatics in the United States can be traced closely to a number of stateside botanical institutions, namely St. Louis’ Missouri Botanical Garden and Kennett Square’s Longwood Gardens. Through the leadership of these botanical institutions, aquatics have joined bedding plants and landscape mainstays on the “big stage” of recreational gardening. A far-reaching fascination with these plants and their wonderful ornamental attributes has led to an increase in commercial availability and educational information for the appropriate care of these aquatics.
Nymphaea as a Genus
Nymphaea is not a genus that offers itself up for a head first plunge. The successful cultivation of water lilies, at-home, requires some tinkering and occasionally a bit of luck. Fortunately, these introductory remarks on available selections and the general culture of water lilies should provide a good starting point for your 2009 season preparations for growing water lilies and, hopefully, pique your curiosity toward more detailed study on this topic.
Water lilies are separated, generally, between hardy and tropical varieties. Each group has a unique history in cultivation as well as morphological and reproductive differences. To begin, hardy Nymphaea exhibit a creeping rhizomatous habit with foliage whorls that exhibit entire (smooth), to nearly entire margins on each leaf. The flowers of hardy water lilies come in almost every color except blue and last for 3-4 days. Each flower floats on the surface of the water and has a scent often described as citrus-like.
Nymphaea ‘David’- Hardy day-flowering water lily. Jonathon Hensley My favorite hardy selections include:
Tropical varieties, for comparison, grow in a more manageable, clump-forming habit. Very few could be accurately described as hardy, though some viviparous blue forms have remarkable cold-tolerance. The foliage of tropicals is substantially different than that of the hardy varieties. Tropical foliage margins are heavily serrated, often mottled or spotted, and individual leaves are noticeably larger than those of the hardy varieties. The flowers of tropical water lilies are held aloft. Unlike hardy lily flowers, they do not rest on the surface of the water and furthermore, can be separated into two distinct groups: day-flowering and night-flowering. The day-flowering forms have a perfume-like fragrance and come in brilliant jewel tone colors like blue and purple. The night-flowering forms have a more pungent fragrance to entice night pollinating agents and can often be seen opening at dusk. White and pink forms are particularly useful for evening garden parties and entertainment.
Nymphaea gigantea ‘Blue Cloud’- tropical day-flowering water lily. Jonathon Hensley My favorite tropical selections include:
General Care and Cultivation
The cultivation of these ornamentals does not require much beyond a few generously sized containers (old whiskey barrels work great). Most water lily varieties perform well in 18 to 36 inches of water. It is important to note that once planted, aquatic lilies should remain submerged to approximately 16 inches throughout the growing season. The size requirements for your planting containers should allow for this “relief” type planting, or approximately 16 inches of water above the level of the plant’s crown. Planting water lily crowns or rhizomes in under-sized containers will lead to diminished leaf sizes and reduced flowering. As is the case with most plants, weak and undernourished water lilies will be more susceptible to pest and disease problems.
This pond in Morris, MN contains a mixture of hardy and tropical water lilies. David Zlesak An alternate way to grow water lilies is in a grouped, pool culture. Here, individually planted containers are combined in a large body of water to create a larger, community display. Container separation amongst specimens is important in pool culture to monitor fertility and to check growth as most varieties are strong competitors during the growing season and will vigorously compete for habitat dominance. Without individual container plantings, the most vigorous varieties will out-compete dwarf selections, etc. It is also important to remember that traditional soiless media components should not be used in aquatic lily culture. Traditional components such as perlite and peat will float and therefore cannot be relied upon to support or nourish aquatic species when grown in a container. A strong field soil is best.
As the growing season progresses, it is important to groom water lilies and feed them on a regular basis. Fertilizer spikes and pellets should be purchased through aquatic suppliers and applied to the individual containers, underwater and directly to the soil. Timing for fertilization involves a number of factors, but generally, checking foliage for chlorosis or nutrient deficiency can be a great way to judge fertility needs. Also, reduced plant vigor will indicate low fertility. Aquatic lilies are heavy feeders and mineral toxicity concerns are rare for the genus Nymphaea. Standard water soluble fertilizer formulations and other typical landscape fertilizers should not be used for aquatics. The weekly care of water lilies involves a detailed and judicious removal of yellowing, overly mature leaves and flowers. Dead-heading with aquatics serves the same purpose as with more traditional ornamentals. Carefully, a sharp knife should be used to trace the older leaves and petioles back to the crown or rhizome of the plant. Similar to a traditional pruning cut, the petiole should be severed cleanly a short distance from the crown, giving care to avoid injuring the plant’s growing point or introducing unnecessary wounds. Overly-mature flowers should be removed with the same technique. The pedicel of the flower should be traced back to its axis, or point of origination, and severed a short distance from the crown/rhizome. With the appropriate care, your newly potted lilies will mature and brilliant, aromatic flowers will reward your efforts through the early, light frosts into autumn.
Over-wintering hardy varieties can be accomplished by dropping individual containers (in pool culture) to the bottom of your pool after the foliage yellows in late fall. These containers, in turn, can be brought back near the surface in spring once new growth starts. In the case of single container specimens, the rhizomes should be lifted after frost and stored in damp sand at 45 to 50˚F. The over-wintering of tropical, clump-type varieties is slightly more involved and usually includes separating smaller viviparous “pups” or collecting seed. It can be very difficult to over-winter large mature plants and it is generally better to start each season with vigorous, juvenile material. If over-wintering tropical starts cannot be achieved with winter lights and heat, purchasing new juvenile material the following spring should be considered. Some unique tropical varieties exhibit the rhizomatous growth habit of hardy varieties. These selections can be over-wintered, as well, with rhizomes stored in damp sand at 45 to 50˚F. In early spring, over-wintered rhizomes can be re-potted in the manner described above and years of successful growing can be achieved.
Nymphaea ‘Aquarius’ (Longwood Hyb.)- tropical day-flowering water lily. Jonathon HensleyThe world of aquatic water lilies can initially seem quite foreign. With some ingenuity and a season or two of experience, you may find that water lilies have a deserved spot in your at-home garden. More detailed resources are widely available on this topic. For more information on aquatic lilies and for follow-up study on over-wintering techniques, propagation, and water lily cultivation, check out these fine water gardening books:
Heritage, Bill. 1986. Ponds and Water Gardens. Poole, New York: Blandford Press.
Perry, Francis. 1961. Water Gardening. London: Country Life.
Uber, William C. 1988. Water Gardening basics. Upland, California: Dragonflyer Press.
Rampant wisteria gloriously consuming arbors and gazebos and laden with clusters of pendulous clusters of lavender/purple flowers throughout summer is no longer just a pleasant daydream for Northern gardeners. Thankfully the hardiest members of Kentucky wisteria (Wisteria macrostachya; macro referring to large and stachys to the elongated raceme of florets) can not only survive, but thrive in zone 4 Minnesota. Native to the Southeastern United States, Kentucky wisteria and its close relative American wisteria (W. frutescens; frutescens referring to the more bushy, compact floral structure) offer gardeners in cold climates wonderful alternatives to the traditional, but less hardy East Asian wisterias- Japanese wisteria (W. floribunda) and Chinese wisteria (W. sinensis).
Minnesota-hardy Kentucky wisteria has gained in popularity and availability primarily due to the efforts of Betty Ann Addison, co-owner of the former Rice Creek Gardens, and her lavender-flowered cultivar ‘Blue Moon’. Her passion for unusual plants and plant selection have resulted in hundreds of new cultivars being introduced to horticulture over the decades from Rice Creek Gardens. ‘Blue Moon’ resulted from a seedling she raised from another Kentucky wisteria informally passed around by passionate Minnesota gardeners. ‘Blue Moon’ is currently being propagated and sold by a few major wholesale nurseries and is becoming increasingly available. In addition to ‘Blue Moon’, the cultivars ‘Aunt Dee’ (also possessing lavender flowers) and ‘Claire Mack’ (a white flowered form) of W. macrostachya are available. Although consistently surviving in the Twin Cities and capable of producing flowers, these other cultivars routinely display greater stem dieback than ‘Blue Moon’. Current breeding work with these hardy wisteria cultivars should lead to even more hardy wisteria options in the future.
‘Amethyst Falls’ is a selection of American wisteria becoming more widely available and young plants have successfully survived this past winter in St. Paul. As more are planted and have an opportunity to mature, we will gain a better idea of this cultivar’s hardiness and performance. It differs from the cultivars of Kentucky wisteria primarily in that the lavender flower racemes are more compact (about 6-8” long versus 10-12”).
Wisteria performs best in locations receiving half a day or more of full sun. Although it is tolerant of many soil types, it does best in moist, yet well draining soil with a neutral to slightly acidic pH. Like other members of the Leguminosae family (pea or legume family), it has the ability to form a symbiotic relationship with nitrogen fixing bacteria. Native to moist areas near wetlands, it has low tolerance to extended drought and benefits from supplemental irrigation, as do many other garden plants. When deciding where to place a wisteria, it is important to consider that it is an aggressive grower that develops a significant woody structure. Supports (arbors, trellises, etc.) must be able to accommodate the weight of the plant. Although hardy wisteria cultivars can readily grow to 15-20’ feet in length in Minnesota, they can be pruned to keep them much smaller.
Wisteria requires a commitment to routine pruning to keep its growth constrained and plants flowering throughout summer. Once established, new canes can grow up to ten feet in a single season! If left on its own, a plant produces many, vigorous stems that grow over each other and neighboring plants. Such plants typically have poor rebloom after the main June display and they invest primarily in vegetative growth. Training and pruning of wisteria shares a lot of similarities to pruning grapes. The main difference is that grapes are pruned in early spring, while wisteria benefits from multiple pruning events throughout the summer.
Main stems can be trained against and over supporting structures and then unwanted, vegetative side branches can be headed back to encourage branching. Some of the new side branches will terminate in flowers after about a foot of growth, while others remain vegetative and can be headed back again or trained as an additional structural stem. Two or three times pruning throughout the summer will help keep a wisteria in bounds and blooming well. Spent flowers can be removed or left in place to develop into attractive pea-like pods with seeds comparable in size to beans. Discontinue pruning in late August to help plants harden off for winter.
Since wisteria stems tend to twine around supportive structures, it is very difficult to detach them and insulate them like one would consider doing for a tender climbing rose or a tender grape. This is why these hardy forms of wisteria are so valuable to us here in Minnesota. Don’t be alarmed come spring if your wisteria doesn’t start growing right away. Sometimes plants can be a little bit slow to resume growth. After new growth starts, one may discover some tip dieback that can be pruned off on especially the vigorous, actively growing canes going into winter. However, for ‘Blue Moon’, dieback in most situations has generally been minimal.
Wisteria can be easily propagated through seeds or cuttings. Although seeds readily germinate if first nicked to help them absorb water, seedlings need to transition through a juvenile period and can take several years before coming to physiological maturity and have the capacity to flower. Cultivars are clonally propagated through cuttings or grafting in order to maintain the characteristics of the cultivar and to produce a plant that is already physiologically mature and can flower relatively quickly. Softwood cuttings can be used, but late winter hardwood cuttings are even easier. Hardwood cuttings with at least two buds can be stuck directly in the ground or brought inside and potted in late winter. Starting them indoors will accelerate their growth. Place them in a moist, yet well draining propagation medium and keep the humidity high around the stems with plastic or by other means. After rooting and new growth starts, begin to open the plastic and reduce the humidity in increments over a few days to a week. New plants can eventually be hardened off and planted outdoors the same growing season.
If you are looking for a vigorous, fragrant, perennial vine for a sunny location with a long flowering season, one of these hardy selections of wisteria may be just the plant for you!
When we think of insect damage to our lawns we usually first think of white grubs. Although not as common, bluegrass billbugs, Sphenophorus parvulus, can also be a problem in turf. However, Extension turfgrass faculty at the 2008 Iowa Turfgrass Field Day this past July noted that bluegrass billbug damage has been steadily increasing over the last several years in Iowa. In some instances damage has been reported to be as serious as that caused by white grubs. Whether or not that same trend is also occurring in Minnesota is unknown at this time.
A bluegrass billbug overwinters in protected sites as an adult and becomes active in May. This weevil is 1/4 inch long, brownish to black with a conspicuous long, curved snout. Once the adult is active in spring, it lays eggs in grass sheaths. These eggs hatch into whitish, legless grubs with brown heads which bore into the grass stems. They eventually reach the roots, measuring between 1/4 - 2/5 inch long as a mature grub. The larvae feed until July and then exit to pupate in the soil. They eventually emerge as adults in August or September. There is one generation a year.
Damaged areas of lawn are usually visible in July and August. First the grass yellows and then eventually turns brown or straw color. Initially, individual grass stems are killed but the damage can spread and irregularly shaped large clumps of lawn can be affected. On higher cut lawns the damage looks like a rather diffuse patch of dead grass stems, while symptoms on lower mowing heights generally appear more distinctly circular in shape. Where feeding levels are high, damaged areas may coalesce together, such that the appearance of individual patches is much less apparent or lacking altogether.
Bluegrass billbug damage on low cut turf. Bob Mugaas
Bluegrass billbug damage is particularly common around sidewalks, driveways, retaining walls, and other heat sink sources. While these heat sink areas are common places for symptoms to be found, it is possible for symptoms to show up in sunny areas of the lawn unrelated to any particular hardscape feature. This damage can be confused with white grub feeding, drought, disease or other lawn problems.
To verify you are dealing with bluegrass billbugs, pull on a browned stem - if the stems break easily at ground level, then it is likely to be bluegrass billbug. You can also look for frass in hollowed out grass centers. If you look right away when you first see damage, you may be able to see grubs in the soil.
By the time you see damage it is too late to treat the problem - the best time to apply an insecticide is in the spring when the adults are active. Scout for their presence when it first starts to get warm. Walk around your yard and particularly watch nearby sidewalks and driveways for their presence in May. Treat when you first see adults. If you have a history of bluegrass billbug damage, treat in the spring after it has warmed up, even if you do not necessarily see adults.
Effective insecticides are imidacloprid, imidacloprid/B cyfluthrin, permethrin, and bifenthrin. Be sure the product you wish to buy is labeled for lawns. If you miss treating in the spring, it is not effective to try to manage them later in the season.
Emerald ash borer (EAB) is a devastating insect pest of ash trees in North America. It attacks all ash species, boring into and killing them. Once a tree is attacked by this insect, it is killed typically in two to four years. All trees are vulnerable, whether they are large or small, stressed or healthy.
EAB killed tree. Jeff Hahn
EAB was unexpectantly found in the eastern side of Michigan’s Upper Peninsula (UP) which also places it closer to Minnesota. It was detected in Houghton county in the town of Laurium, just south of Calumet as of August 7. As in Wisconsin, this infestation was discovered when a property owner reported dead ash trees. It is likely in both Wisconsin and the UP that these infestation were present for five years or more.
Missouri found EAB for the first time in July in the southeast part of the state. Officials also found EAB in July in Bloomington, Illinois, about 65 miles south of the previous most southernly site in Illinois. Although apparently eradicated in 2003, EAB was found again in Virginia in July.
What does this mean for Minnesota? Should we be treating our trees to be on the safe side? Definitely not! As long as we do not actually have a confirmed infestation in Minnesota, it makes little sense to treat ash trees with insecticides. The chemicals currently at our disposal require a yearly application either into the soil or injected into the trunk. Such treatments, in the absence of a confirmed infestation, will likely add years of unnecessary applications and expense.
People will not be automatically advised to treat their ash trees even when EAB is found in Minnesota, unless you are close to an infestation. University experts throughout the EAB-infested states do not advise insecticide treatments without a confirmed infestation within 12 - 15 miles.
It is true that infestations in other states usually have gone undetected five years or more before they are discovered, which might be the case in Minnesota. However, that still does not justify preventative treatments. EAB does not kill every tree in an area overnight and there will be enough time to react once EAB is actually found here. So what can you be doing in the mean time to help in the fight against emerald ash borer?
One of the most important ways you can help is by not moving firewood even within Minnesota. Hitchhiking in firewood is the primary method emerald ash borer has for moving into previously uninfested areas. Always buy firewood locally from approved vendors and don’t bring firewood home with you, either burn it or leave it at the site from which you bought it.
Be on the watch for ash trees that are dying for unknown causes. Many first detections are made by the general public who have reported suspicious symptoms in their ash trees. You can go to the Minnesota Department of Agriculture web site, http://www.mda.state.mn.us/plants/pestmanagement/eab.htm for information on how to recognize emerald ash borer, look-a-likes (not all green insects are emerald ash borers), and the symptoms of emerald ash borer
Potted chrysanthemums, asters, and flowering kale have become staples to add fresh excitement to the fall garden. They have been readily available since early August in garden centers and are affordable options to add colorful accents to tired areas of the landscape. There are many other plant materials we can use for added fall color besides this faithful group of seasonal favorites. One out of the ordinary option is fall blooming bulbs. Among these fall blooming bulb favorites are Colchicum spp., Crocus spp., and Scilla spp. They are ready to flower soon after planting and need to be planted as soon as possible. Look for them in local garden centers displayed next to spring flowering bulbs or order them from specialty bulb companies. If left to wait too long before planting, they begin growing and may even flower within their packages.
These fall blooming species provide great splashes of color and are great used in pots, rock gardens, window boxes, or other places where their compact size, yet spectacular color and flowers can be displayed to advantage. They typically flower without producing much or any foliage. They are adapted to flower in the fall and produce their foliage in the spring, just like their spring flowering relatives. There is variability among cultivars for these species for winter hardiness (some are zone 4 hardy, while others are not). Use some mulch for winter to provide extra insulation to help the more marginal bulbs survive. Potted bulbs can be planted out in the garden after flowering.
Colchicum spp. look similar to crocus and are often confused with crocus. Many produce multiple flowers from a single bulb and flowers tend to come in warmer colors than most crocus such as fushia and lilac-pink. Some are even double-flowered. Colchicum spp. produce a toxic substance called colchicine and they should not be used in areas where children or others tempted to eat plants would encounter it. Colchicine at controlled doses have been helpful in the treatment of gout. In addition, in the 1930’s it was learned that it can increase the chromosome number of plants and also induce mutations. Colchicine interferes with cell division and disrupts chromosomes. Colchicum spp. produce a wonderful flower display and are safe under normal circumstances, as are many other plants producing toxic compounds like datura, caster bean, and oleander.
There are many wonderful fall blooming crocus species. They tend to come in cooler colors compared to Colchicum species, typically shades of lavender, purple, and white. One easy way to tell members of the genus Colchicum and Crocus apart is that Crocus spp. have three stamens, while Colchicum spp. have six. One of the most famous of the fall blooming crocus is C. sativus, the saffron crocus. Grown for centuries, it is the species from which the treasured spice saffron is collected. The style of the flower (part of the female portion of the flower) is collected and dried for this spice.
Fall blooming Scilla species have a different look than the above two genera. Many small flowers are borne along a central stem, just like the widely grown spring flowering Siberian squill (S. siberica) here in the North. Scilla spp. tend to readily naturalize by propagating from both seed and bulb offsets.
Another late summer to fall blooming favorite is Lycoris squamigera, the resurrection or magic lily or sometimes called naked ladies. It is within the amaryllis family. Leaves emerge in spring and persist into early summer before dying back. Flowering stems are typically evident in August into September. The flowers are typically pink and look much like our traditional houseplant amaryllis flowers, only smaller in diameter. They are often listed as hardy to zone 5, but in protected areas they have faithfully survived in Minnesota gardens.
Consider adding an interesting twist to the fall landscape with fall blooming bulbs.
Have you noticed unusual yellow rings, spots or blotches on your shade tree’s leaves this summer? If so it may be caused by one of the new tree infecting viruses recently discovered by University of Minnesota plant virologist, Dr. Ben Lockhart.
Viruses that infect plants are organisms so small, that they can only be seen with a special high powered microscope called, an electron microscope. Trained virologists, like Dr. Lockhart, recognize new viruses by the symptoms they cause in infected plants. Virus infected plants may have random patterns of yellow and green called mosaic, rings spots of various colors, crinkled or distorted leaves, or a variety of other symptoms. If a virologist suspects a plant is infected with a virus, they take leaf samples back to the laboratory and run several different tests to look for the virus.
In three separate cases in Minnesota, trees exhibiting strange yellow patterns on their leaves were indeed infected with a virus. When Dr. Lockhart finds a new virus, he asks several questions. What plants will the new virus infect? How is the virus carried from one plant to another? What type of damage will the virus cause in an infected tree? Finding the answers to all of these questions may take years.
Ash Mosaic Virus, one of newly discovered viruses found in Minnesota and several other states, causes ring spots to form on ash tree (Fraxinus spp.) leaves in August and September. These spots become more dramatic as the leaves change color in the fall. This virus can infect white, blue, black and green ash trees. To learn how the virus is transferred to new plants, seeds were taken from infected trees and grown into seedlings. These new seedlings were tested for virus infection. Out of 100 seeds, none of the seedlings carried the virus. From these results, Dr. Lockhart suspects that the virus cannot move from parent to seedling through the seed. Examining the morphology of the virus, he noticed that this virus is very similar to viruses carried from plant to plant by mites, tiny arachnids that feed on plants. Although he suspects Ash Mosaic Virus may be transmitted by mites, this theory still needs to be tested. Many of the ash trees that Dr. Lockhart found infected with Ash Mosaic Virus were declining trees. However it is still not known if the virus causes the trees to decline, or if it is just one small factor in many.
Hackberry Island Chlorosis is another virus recently found, and is apparently quite common across Minnesota. Hackberry Island Chlorosis causes yellow to white random blotches to form on the leaves of hackberry trees (Celtis occidentalis). Virologists have suspected for years that hackberry trees with these symptoms had a virus. Until recently however, nobody had been able to find the virus itself. Dr. Lockhart is just now learning about the virus. He suspects that the virus is transferred from plant to plant through seed or through a very common insect because even very young hackberry trees have been found to be infected. Elm trees (Ulmnus spp.), a close relative of hackberry trees, do not get the virus.
Several young quaking aspen trees (Populus tremuloides) were sent to Dr. Lockhart because the leaves were crinkled, curled and had random green and yellow patterns. After running several tests, Dr. Lockhart was surprised to find that although these symptoms were caused by a virus, it was not a new virus. The virus infecting the aspen trees was Spirea Yellow Leaf Spot Virus. This virus, although very common in spirea shrubs (Spirea japonica), had never been reported in aspen trees before. Although many viruses can infect several members of the same plant family, it is unusual for a virus to infect unrelated plants like aspen and spirea. Spirea Yellow Leaf Spot Virus causes yellow spots, twisted, and unusually small leaves on spirea shrubs. The virus is transferred from plant to plant by an aphid.
Although trees infected with a virus can never be cured, it is still unknown how severely these viruses will affect the overall health of the tree. Dramatic symptoms on the leaves may only be a ‘sniffle’ to the tree, or could turn out to be far more serious. Research will continue at the University of Minnesota to learn more about these viruses and the diseases they cause.
September is a great time to dig and divide peonies. Try to save as many roots as possible when digging them. Carefully wash off the soil and cut the clump into divisions that have at least a few swollen eyes- growing points for next year’s stems. A sharp knife or small saw can help maneuver within the plant. Recently divided peonies may or may not flower the next growing season. When replanting peonies be sure to place the eyes no deeper than an inch deep. Fall is also a good time to divide iris.
Continue to irrigate trees, shrubs, and perennials if rainfall is scare to minimize stress as plants go into winter. Avoid letting plants develop drought symptoms before accommodating their moisture needs.
Begin to transition houseplants back indoors for winter. Many houseplants are tropical plants that not only are damaged by frost, but also temperatures below 50oF which easily occur during the night. Inspect plants closely for insect pests before taking them indoors. Consider insecticidal soap or other labeled pesticides to try to reduce pest problems before bringing them indoors.
Consider adding some spring blooming bulbs to your landscape. David ZlesakLocal garden centers have a great selection of spring flowering bulbs. Consider where you can include some in outdoor beds and also how many you would like to force and enjoy indoors this winter. Some species of bulbs are longer lived and can serve as longer lived investments than others. Some of the shorter lived species include hyacinths and some tulips. Daffodils and Siberian squill tend to be longer lived. Spring flowering bulbs are a much welcomed site come spring.
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Happy gardening!David C. Zlesak, Ph.D.
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