|Yard & Garden Line News
Volume 5 Number 15 October 1, 2003
Rooting Around: Tree Roots
Dave Hanson, Urban & Community Forestry
Take a good hard look at your favorite tree. What do you see? Nice form, leaves, branches, bark, but, how many would respond - "Oh baby! There must be some fine roots holding up this tree."
Large perennial, bur oak support roots exposed by erosion. |
Unfortunately for trees, not too many people respond in this fashion, the world underground does remain a mystery. What is happening down there? What are tree roots and for that matter where are the roots? Why and how do roots get into sewers, cause foundations to crack and sidewalks to lift? The reason that these mysteries remain: we cannot easily see and touch tree roots, we cannot readily access them and typically we do not encounter them without getting out a shovel. This brief article will skim the surface, so to speak, and attempt to provide some insight and answers to these questions.
So, let's start at the beginning and address two basic questions. Question number one, what are tree roots? There are three basic types of tree roots: Structural support, Fluid transport, and nutrient / moisture absorbers. Structural support comes in the form of larger-diameter perennial woody roots that anchor the tree to earth. Near the base of the tree are found the sinker or striker roots that help stabilize the tree and help it exploit deeper soils, but they seldom extend below 1 meter deep (Harris et al.). A second group of perennial support roots grow horizontally radiating away from the tree and also provide transport of nutrients, water and oxygen to the canopy. In return, the canopy delivers energy back to the roots for their use and for storage. The last of the basic root structures to discuss here are referred to as absorbing roots (fine root hairs and the root tips roughly 1/16th inch diameter) that provide nutrient and moisture absorption for the tree.
With that basic understanding, let's move on to question number two. Where are the roots of a maturing or mature tree? Many consider the drip-line of the tree to be the limit of the root spread; therefore, the assumption is made that this is the area to fertilize and water for the benefit of the tree. A better mental picture to form is a wine glass positioned on a dinner plate. In support of this mental picture six species, including green ash, maple, and oak, were studied by Dr. Edward Gilman of the University of Florida. Dr. Gilman and associates performed root growth trials in Florida and New Jersey. The findings clearly debunked the "drip-line" notion of tree roots. On average they found that tree roots extended 3 times the spread of the branches and that more than 50% of the absorbing roots were beyond the drip-line.
Graphic from Tree Roots, ISU Forestry Extension
Several numbers can be found in the literature concerning where the bulk of fine, absorbing roots are found in the soil profile. The stated depths range from the top 24 inches to the top 18 inches with 50% of the fine roots being in the top 6 inches of the soil profile. Dr. Gilman's research tightens these numbers up considerably. From the same root growth trials in Florida and New Jersey Gilman states: "fine roots are concentrated in the top 12 inches of soil with many in the top 2 inches."
Okay, so some trees have roots near the soil surface to collect nutrients and moisture. "But, I've never watered my tree because its taproot gets all the water it needs from the Saint Peter sandstone aquifer." There are species that as seedlings produce and rely on tap roots, but quite honestly, as "tap-rooted" species mature, tap roots become insignificant in the overall root structure. The bulk of nutrient and moisture uptake is taken over by the absorbing roots near the surface.
Tap roots and other "sinker" roots can penetrate into the soil layers, but research indicates that depth of rooting is dependant on soil-oxygen. Dr. Kim Coder from the University of Georgia states that good root growth requires a soil atmosphere of 15 percent oxygen. He continues by saying that below 5 percent soil-oxygen, root growth will stop and below 2% roots begin to decline and die. Dr. Coder describes the advancing root tips existence as quite precarious and more of a "good news / bad news" scenario. If the root progresses too deeply, oxygen deprivation will be an issue and on the other extreme if a root progresses too shallowly, a dry spell will likely cause its demise. As a matter of fact, this precarious situation translates into a short life span for an absorbing root with the root tip being replaced many times per growing season.
|University of Minnesota, TRE nursery Planting Depth Study. After three years in the ground, these linden root systems show the results of being planted ten inches too deep. Note the roots returning to the surface - Speculation: the roots were growing towards a higher soil-oxygen concentration.
The bottom line, unlike horses, roots do not smell water. Along the same line, roots do not seek water. Instead, roots tend to grow where the growing is good and the growing tends to be good in the top 12 inches of soil where temperature, moisture, nutrients and more importantly soil-oxygen are usually adequate. To underline the fact that roots are opportunistic "absorbers" - there has been a push lately to discourage calling fine absorbing roots, "feeder roots" simply because the term "feeder" implies an aggressive, hunter-gatherer approach to seeking life's necessities. Roots simply follow the moisture gradient of the surrounding soil and continue to grow where the growing is good. Meaning that roots tend to grow where there is a good supply of moisture, nutrients and of course soil-oxygen.
Now is the time to step back and put this information in perspective. Tree roots require oxygen to remain viable and soil-oxygen decreases the deeper in the soil profile that a root penetrates. Add in soil compaction to your thought process. By compacting a soil the pore space is reduced which in turn reduces the amount of soil-oxygen that can be present. Okay, one more thing - re-landscape the lawn with a bobcat and add 4 inches of soil to bury the roots a little deeper. Hold on, the lawn typically means turf and that means roots from grass and competition for moisture, nutrients, and you guessed it soil-oxygen. The picture should be coming clearer, tree roots, all too often overlooked, spread as far and as wide as they can in compacted soils and at depths below 12 inches trying to survive. Keep in mind that this is biology, and the ultimate root structure depends on many factors below ground. Site conditions, compaction, excess fill, flooding and infrastructure have direct and indirect impacts on soil moisture, soil oxygen, soil texture and structure.
Moving on into the second round of questions: It has happened again! Another basement floods because a sewer line has been clogged by tree roots. Maybe this time it is another foundation or sidewalk being moved or lifted by tree roots. Are trees "perpetrators" of these acts or is it simply guilt by association. One side of the argument states that the tree and its roots are not at fault, but rather there is fault with the design or construction of the infrastructure.
Honesty is probably the best policy; trees are not as innocent in the above scenarios as many of us would like to believe. However, why has the tree become the guilty party? Design error is often the only answer to be arrived at whether it is the landscape design or the engineering design. Let's face it, trees require space for rooting and resource exploitation, if a tree root happens upon a nice moist, oxygenated resource-rich environment (a sewer line for example) where it can thrive and perform its duties - it will. In commenting on tree roots in sewers Richard Harris et al. states "the conditions of aeration, moisture, and nutrients are so favorable that it inevitably grows until it clogs the sewer." The question in many minds still remains as to how the root happens upon the sewer line.
Martin Mackenzie of the US Forest Service recently spoke to a conference audience describing the "battering-ram" root that breaks through even the toughest sewer lines and concrete blocks. Of course this statement was "tongue-in-cheek." Roots grow quite slowly and don't have much chance to hurl forward with any great speed. In the case of finding a sewer line there is both speculation and research that explains the encounter. Speculation from Harris et al. is that in some instances sewer line trenches are compacted to a lesser degree than the surrounding urban soil. Thus, homeowners may unwittingly take advantage of this and plant trees in the trench or perhaps the tree roots will encounter this less compacted environment and continue to grow into it unimpeded. Dr. Kim Coder researched the thermal gradients that exist between sewer lines and the surrounding soils which allow two things to happen. One is a moisture condensation layer on the sewer line itself. Secondly, a moisture condensation column develops in the soil layers above the sewer line. Once a tree root encounters this moisture condensation column it grows downward (providing adequate soil-oxygen exists) along the increasing moisture gradient in the soil toward the sewer line. Upon encountering the sewer line, the root tips continue growing towards more favorable conditions, eventually a root tip may find and exploit a crack or fissure in the sewer line. Hence, back to the argument proclaiming faulty infrastructure - "the root tip exploits a crack or fissure in the sewer line."
Once the root tip has entered the line, the real damage to the line can begin. The tree roots tend to form a mass of root tips that slow the flow enough to allow sediments to be trapped, thus clogging the line. Or the root may begin to develop as a woody, perennial root and exert pressures that may crush or burst the sewer line.
Larger, woody, perennial roots exert substantial radial pressure and over time can displace man-made structures. The perennial root increases in diameter by adding a growth layer every year. Commonly, sidewalks are lifted by this type of radial growth. Displacement of structures can be caused by horizontal roots growing under a slab concrete floor or sidewalk or by a vertical "striker or sinker" root growing downward next to a foundation. In any case the root growth is slow and forces can be substantial enough to displace or otherwise damage structures.
Another mechanism by which trees cause structural damage involves the presence of expansive clays. Expansive clays respond to soil moisture changes by expanding and contracting. Man-made structures often rely on the surrounding soils for additional support. If a tree's roots encounter this "support soil" of expansive clay the moisture regime can be dramatically altered by the evapo-transpiration function of the tree. The clay soil type can be dried excessively causing it to contract, thus shrinking away from the structure it is supporting.
The literature identifies several tree species as "culprits" in the "aggressive" root department. The following species are on a "Not Recommended for Planting" list maintained by the Michigan Department of Natural Resources as those having invasive rooting habits: silver maple (Acer saccharinum), white mulberry (Morus alba), white poplar (Populus alba), Eastern cottonwood (Populus deltoides), weeping willow (Salix alba), black willow (Salix nigra), and American elm (Ulmus americana). Is it necessary to "label" these trees as culprits and black list them? A better approach is to pay attention to putting "the right tree in the right place." More and more attention is being paid to tree selection since it is the "key" to a trees long life. Site conditions truly need to be considered prior to starting the species selection process. It isn't always successful to fall in love with a species and then try to fit it in our landscape.
In wrapping all of this together, a number of additional questions come to mind. For instance:
*What does all of this say for our notion of watering and fertilizing within the drip-line?
Yes, the water and fertilizer helps, but in
light of root plates reaching well beyond the crown - consider expanding the applications to a broader area.
*With a tree's absorbing roots concentrating near the soil surface, how well do the trees and turf co-exist?
Trees and turf are in a competitive battle for resources and let's face it - turf is a tough competitor. From a trees perspective: The more lawn that can be replaced with mulch the better.
* What does this portray for trees when parking lots, sidewalks, driveways, buildings, roads and other infrastructure are placed in close proximity to trees?
These structures almost always require a compacted base layer to provide additional support for the impervious surface being applied. The needs of the tree and the reach of the root plate are too often ignored leaving trees with reduced stability and with reduced capacity to uptake nutrients and moisture.
There is some good news out there… Recent methods of constructing sewer lines have dramatically reduced the potential for root intrusions. Longer sections of less porous pipe are being used for constructing sewer and water lines. This helps cut down on the conflict between tree roots and sewer lines that often results in a large, mature tree being removed.
Researchers and trials in California are looking at composite sidewalk surfaces that flex, thus giving trees room to grow and more soil to exploit for resources.
Researchers at Cornell University have been testing and working with CU Structural Soils® for some time. These soils are compactable, yet allow tree roots to penetrate. Placing these structural soils in the rooting zone under sidewalks, pavers, parking lots, roads and other structures allows trees to expand root plates farther.
So, next time you look at your favorite tree - give some thought to the root structure. You may not have the, "Oh Baby!" type of reaction, but after reading this article the roots should at least be creeping into the outer recesses of your mind.
For More Information:
Bassuk, Nina. Cornell Structural Soil. Internet. Available 9/25/2001. http://www.hort.cornell.edu/department/faculty/bassuk/uhi/outreach/csc/
Coder, Kim D. Tree Roots and Infrastructure Damage. Internet. Available 9/25/2001. http://www.forestry.uga.edu/warnell/service/library/for98-008/index.html
Coder, Kim D. "Don't Stumble Over Surface Tree Roots" Grounds Maintenance. August 1 1998
Gilman, Edward F. Where are Tree Roots? Extension Service Bulletin ENH 137, Florida Cooperative Extension Service, University of Florida, Institute of Food and Agricultural Sciences. Internet. Available 9/25/2001. http://edis.ifas.ufl.edu/BODY-WO017
Harris, Richard W., Clark, James R., Matheny, Nelda P., Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines. Third Edition. Prentice-Hall, Inc. 1999.
Graphic, ISU Forestry Extension. Tree Roots October 2001. Internet. Available 9/25/2001. http://www.ag.iastate.edu/departments/forestry/ext/roots.html
Pool, Bob."With Rubber Sidewalks, Trees Are on the Rebound," LA Times. 14, July 2001. Internet. Available 9/25/2001. http://www.mindfully.org/Plastic/Rubber-Sidewalks.htm
Randrup, Thomas B, McPherson, E. Gregory, Costello, Laurence R. "Tree Root Intrusion in Sewer Systems: Review of Extent and Costs." Journal of Infrastructure Systems, Vol 7, No. 1, pages 26-31. March 2001.
Soil Compaction: Causes, Effects, and Control. 2001. Internet. Available 9/25/2001. http://www.extension.umn.edu/distribution/cropsystems/components/3115s01.html
Check Mulches Around Woody Plants
Deborah Brown, Extension Horticulturist
Before weather gets too brutal, it's a good idea to check mulch levels around woody trees and shrubs in your landscape. If the mulch has packed down over the past growing season or two, add some more before the soil freezes or it's grown so nasty out that you're tempted to skip it.
Properly mulched tree.
Irrigation bag at base.
Shredded bark, wood chips, and other organic mulches should be kept at a depth of about three to four inches for maximum benefits. Leave a little space around trunks and stems, though, for good air circulation. Mulch that abuts trunks and stems directly may keep them too moist, encouraging mold.
Last year's "open winter" in which we had little or no snow cover for most of the season really reminded us of the wisdom of mulching all perennial plants – both woody and herbaceous – in our climate. This year's extremely dry summer just reinforced it.
If you've put in any new woody landscape plants in the past few years, and especially this year, it's doubly important that you mulch them well. That layer of mulch will allow you to continue watering them later into the season, because it will keep the soil from freezing as early as it might otherwise.
If you're growing tender hybrid tea roses or others that need protection, try to take care of them around the middle of the month. They'll be okay down to about twenty degrees Fahrenheit, but after mid-month there's a good chance temperatures may dip lower than that.
As for those herbaceous (non-woody) perennials, you can add to the mulch around them now, but wait until the soil begins to freeze (usually some time in November) before covering them for the winter. Straw, leaves, and even grass clippings, are among the many mulching materials you can pile on top of perennials to protect their roots from excessive cold. Strangely enough, by insulating the roots, mulch also protects the plants from early warm-ups and alternate freezing and thawing cycles.
We're due for a little luck; let's hope for plenty of snow to protect our plants this coming winter. But don't rely on luck alone. Add mulching to your list of fall garden and landscape activities.
Minnesota Gardening Calendar Available Again
Deborah Brown, Extension Horticulturist
Check local book and gift stores for copies of our newest calendar, Minnesota Gardening, 2004. It's cover is a bit of a departure. Look for a close-up of yellow garden lilies that "pop" from a dramatic black background.
2004 Garden Calendar
Along with a series of useful garden and landscape tips for each month, the calendar features a page about growing fruit trees in northern climates. It lists many of the best cultivars, along with which parts of the state you can expect to succeed with them.
To view some of the photos and monthly tips, or to order calendars on line, go to:
Gardens Painted with Ladies
Jeff Hahn, Assistant Extension Entomologist
Many gardens in Minnesota were treated to an explosion of color in the form of painted lady butterflies. Minnesota has struggled through a very dry summer which was partly relieved by rain on September 11. Many painted butterflies had been avoiding the dry weather by remaining in their chrysalises. Once the rains arrived, this triggered a mass emergence.
In a normal year, painted lady butterflies would emerge throughout July and August so you would see a steady, less spectacular number of them. Although actual butterfly numbers were estimated to be average, they seemed to be much more abundant because so many appeared at the same time.
Painted lady butterflies are very common throughout the U.S. and are usually found in open habitats. They are a moderate sized butterfly with a wingspan of about two inches across. Their wings are orange and black with spot spots. They have been erroneously called ‘miniature monarchs' despite the fact that the two are not that closely related.
The larvae have a dark head and a grayish brown body with yellow stripes with numerous yellow barbed spines. The are about one inch long when fully grown. The larvae feed mostly on thistle, including weed thistles and ornamental thistles. They may also eat other plants, including burdock, sunflowers, groundsel, pearly everlasting, Helianthus, Artemisia, and hollyhock. A larva feeds singly inside a ‘nest' they construct by webbing together several leaves.
Unlike most butterflies found in Minnesota, painted ladies do not survive winters here. Next year, a new generation of butterflies will migrate north and east from California, arriving sometime in May or June. This migration can be quite spectacular. Once they arrive in Minnesota, there are usually two generations during the summer.
Geranium Bud Caterpillar
Jeff Hahn, Assistant Extension Entomologist
Many gardeners experienced an insect attacking their geranium buds from late August through September. They have also been reported attacking petunias. The caterpillar has been identified to the family Plutellidae (diamondback moths), although the species is not known. There are also no records that could be found in the literature of such a caterpillar on geraniums.
Damaged geranium bud
The larvae are brownish with a white stripe along each side. There are also numerous erect hairs on their body. After these caterpillars fed in the buds, their bodies take on the color of the flowers so that reddish and purplish caterpillars were also found. The caterpillars grow to be at least as large as one inch long.
The caterpillars chewed deep holes in the sides of the buds. Flowers still emerged from these damaged buds but flowers had large holes in the petals. Some leaf damage was noticed but the primary damage was to the buds.
Early detection is very important to effectively manage this caterpillar. Starting in August, inspect your flowers, watching for the caterpillars and damaged buds. Also watch for fecal droppings as this is a tell tale sign of caterpillar activity.
Once caterpillars are discovered, a good option is to handpick them off the plants. You can kill them by crushing them or dropping them into a container of soapy water. You can also treat your plants with a residual insecticide, such as permethrin (e.g. Bonide Eight or Spectracide Bug Stop), carbaryl (Sevin), cyfluthrin (Bayer Advanced Lawn and Garden), or esfenvalerate (e.g. Ortho Bug-B-Gon).
Plutellid caterpillar on geranium.
Insecticidal soap is only effective is you directly hit the insects with it and it doesn't have any residual activity. Bacillus thuringiensis (e.g. Dipel or Thuricide) is also not likely to be as effective. It works when the product is ingested by the caterpillar and then works as a stomach poison. There is little surface when the caterpillar is feeding on the buds so the caterpillar will not consume much insecticide.
Brace Yourself for Lady Beetles
Jeff Hahn, Assistant Extension Entomologist
Multicolored Asian lady beetles, Harmonia axyridis, have been pests in homes in Minnesota since 1998. Although they are beneficial because they are voracious predators on aphids, including soybean aphids, they are also pests because they invade into homes and other buildings during fall.
Multicolored Asian lady beetles.|
Photo credit: Jeff Hahn
These lady beetles first start entering homes in large numbers any time from late September to late October. We will most likely see a lady beetle invasion when temperatures drop down near 32 degrees F and then warm back up into the mid-60's F. Last year, after temperatures first dropped to near freezing it never dramatically warmed back up into the 60's. Although lady beetles still moved into buildings, we never really seemed to have that one defining moment when they first started to enter.
The best way to deal with lady beetles in building is to prevent them from getting into your home in the first place. Once they are in your home, your options are very limited. Keeping these lady beetles out of buildings is a two pronged approach. First, it is important to calk and seal potential areas around the outside of your home where they may enter.
Concentrate along windows, doors, roof lines, the foundation and utility lines. Repair or replace any damaged window or door screens. Screen off vents (use at least 20 mesh). Pay particular attention to the south and west sides of your home, this is where the lady beetles are most likely to enter your home. Although you can not completely exclude lady beetles by caulking and sealing, you can significantly reduce the number that do get inside.
The second phase of lady beetle management is an insecticide application around the exterior of the building. There are number of insecticides that are available to homeowners. Be sure to choose a product that is labeled for treating the exterior of buildings. Sprays should be concentrated along the roof lines, along windows and doors, and at the base of walls. Be sure sprays are applied before lady beetles attempt to enter buildings.
Insecticides available to homeowners for lady beetle control include:
deltamethrin (e.g. Bonide Household Insect Control)
bifenthrin (e.g. Ortho® Home Defense® Perimeter and Indoor Insect Killer)
cyfluthrin (e.g. Bayer Advance Home® Home Pest Control Indoor and Outdoor Insect Killer)
tralomethrin (e.g. Spectracide® Brand Bug Stop® Indoor and Outdoor Home Insect Control4)
esfenvalerate (e.g. Monterey Bug Buster)
permethrin (e.g. Bonide Eight Yard and Garden Ready to Spray)
Deltamethrin and bifenthrin are both very effective against multicolored Asian lady beetles. Cyfluthrin, tralomethrin, esfenvalerate, and permethrin are also effective although the residual may not last as long.
You can also hire a professional pest control service to treat the exterior of your home. They have the experience to successfully control lady beetles. They also have access to many effective products, including Demand CS (lambda-cyhalothrin) which is particularly effective against lady beetles. This product is not available to homeowners.
Once you find lady beetles inside your home, the only real control is to vacuum them and then discard the bags. Spraying lady beetles indoors with insecticides has limited value and does not prevent lady beetle from entering homes. Avoid crushing lady beetles as this can stain surfaces.
Get the low down on this month's insect pests at
OctoberPest: Exploding Pumpkins!
Janna Beckerman, Extension Plant Pathologist
October is a howling good month to talk about pumpkins. But what about exploding pumpkins? No, not the alternative band, Smashing Pumpkins, but a real, exploding pumpkin! As a plant pathologist, I am privy to all sorts of unusual plant disasters, both personal and professional. But nothing I've experienced compares to this one: Last year, in Ottawa, Canada, the owner of Canada's largest pumpkin was about to be crowned the winner, until he saw the fruit of his labor literally blow-up in front of him. As his pumpkin was placed upon the scale, it exploded at its base, forcing a disqualification from the contest.
Without having the good fortune of being there, it is difficult to diagnose what actually went wrong. The fact that the pumpkin exploded, instead of the usual collapse, is a truly notable symptom. Approximately ten years ago, exploding watermelons made headlines, and a bacterial fruit blotch, not Gallagher, was implicated. In the case of pumpkins, however, bacterial soft rot (caused by Erwinia spp) is the most common post-harvest rot affecting pumpkins. This disease causes pumpkins to collapse into a rotten, stinky mess. In order for a pumpkin to explode, the structural integrity of the pumpkin would have to remain intact while gases developed and accumulated. Gas accumulation could develop as a by-product of fermentation, and without any place to escape, the end result could be an exploded pumpkin. But the question remains: How did fermentation begin and why is there no record of other such occurances?
In consultation with several melon pathologists and professional pumpkin growers, and doing some in-depth research, I've discovered the dark, hidden underbelly of the giant pumpkin growing world. We are all familiar with the phenomenon. Whether it is raising prize winning hogs or cattle, the desire to win supplants the desire to play fairly. However, even the rules as to what constitutes "fair play" are open to interpretation according to one giant pumpkin growing website (http://www.homestead.com/henryholman/files/pumpkin_rules.html)
So, I can't say I was too surprised to learn that there is a dark side to giant pumpkin growing. If professional athletes inject themselves with steroids, it is only a matter of time before pumpkin growers attempt the horticultural equivalent: Sugar I.V.s forced upon hapless and defenseless pumpkins. Where is the outrage?
In trying to grow bigger and better, some people resort to pumpkin injections. It is ruled illegal by many of the sponsored "giant pumpkin contests." However, without an obvious entrance hole, it would be difficult, if not impossible to prove such a thing occurred, as any sugar-based solution would be absorbed and utilized by the pumpkin. And at least one professional grower stated that such a practice is completely unnecessary if you are striving for "only" a three-to four hundred pound pumpkin.
However, to obtain the truly monster pumpkin, like this year's 1400+ pounder grown in New Hampshire, many growers have resorted to injections (Let me make one thing clear: I am not saying that this year's winner did such a thing! The last thing I need is a pumpkin libel suit!). And like humans who inject themselves with steroids, a sterile needle and sterile solution are absolutely required. It is most likely, but not conclusively demonstrable, that in the course of injecting the pumpkin, yeast contaminated the sugar solution. This yeast then went about fermenting the sugar injected into and being produced by the pumpkin, which also conveniently provided a warm, dark, otherwise sterile place to turn sugar into alcohol, with a by-product of carbon dioxide. Movement would have increased aeration within the pumpkin, thereby increasing both fermentation and carbon dioxide production. Without a valve to release pressure, the pumpkin would explode.
Pumpkin contest in
Unknown internet site
The judges weighed the giant pumpkin anyway and it came in at 560.5 kilograms, ( 1235.69 lbs.) easily enough to break the previous Canadian record of 547 kilograms. Eaton was quoted to say: "I'm disappointed, but that's life." Except, of course, for the pumpkin!
For more about growing "Giant Pumpkins,"see:
http://www.backyardgardener.com/wcgp/index.html An overall great site for pumpkin growing, it includes the 'Top 100' biggest pumpkins.
The Rules of Giant Pumpkin Growing: http://www.homestead.com/henryholman/files/pumpkin_rules.html
The Cucurbit Network: http://www.cucurbit.org/
October Garden Tips
Beth Jarvis, Yard & Garden Line
Compiled from conversations with Bob Mugaas and Doug Foulk, Regional Exension Educators, and Gary Johnson, Urban and Community Forestry.
Photo credit: Beth Jarvis
Don't mulch strawberries until night temperatures are in the 20s or after a series of consecutive freezes. (This is generally the latter half of November in southern Minnesota.)
Don't touch apples that are frosted. Your warm fingers on the cold flesh will cause discoloration. Wait until the fruit has warmed to pick.
Apples, pears, grapes and plums can tolerate light frost to 26 degrees F. Ripe fall raspberries might be damaged but not developing fruit.
Fall bearing raspberries can be pruned back after fruiting but research has shown that later winter/early spring pruning is best. The nutrients stored in the canes are re-absorbed by the roots.
Clean up fallen fruit and leaves. Destroy diseased plant material. Do NOT compost it.
Protect trunks of young fruit trees from winter damage. A hardware cloth cylinder of 1/4" mesh will deter hungry voles and rabbits. To protect against sun scald, position a board against the south-southwest side of the tree trunk and secure it in place. You can make the hardware cloth cylinder large enough to include the board. Or, you can buy spiral tree wrap.
Enjoy the fall color of the blueberries.
Early October is still a good time to treat broadleaf weeds.
Your last fall fertilizer application should go down around the end of October. The rate is 3/4 to 1 lb. of nitrogen per 1,000 square feet. To calculate the amount of actual nitrogen in your fertilizer see:
Trees and Shrubs:
Containerized trees and shrubs can be planted up to the end of October. Be sure to water them regularly and well and mulch them.
Protect terminal buds of evergreens from deer browse by covering them with bud caps. Index cards/recipe cards can be folded in half and stapled to make the cap. (A 3" by 5" card will make a 2.5" by 3" cap). Place these over any terminal buds you want to protect, especially the main leader.
In later October-early November, you'll want to have your rodent protection in place around young trees and shrubs. Cylinders of 1/4" hardware cloth is the best, though making them is a nasty job. (Wear gloves to reduce cuts and scratches.) The up-side is once they're made, they last forever.
According to recent research, hardware cloth has been shown to reduce frost crack in young trees. It appears to divert enough sunlight to prevent injury. But, to be sure, use a board to shade the south-southwest side of any trees planted within the last 5 years, regardless of trunk size.
With this issue, we return to monthly publishing, on the first of the month.
The photo at left was taken at the Minnesota Landscape Arboretum during the flush of painted lady butterfly emergence. I count at least 4. How many do you see?
Next month, we'll see the results from the Dakota County MG fruit and vegetable trials. At some point this winter, we'll visit the North Central Research and Outreach Center, formerly the NC Experiment Station, in Grand Rapids.
Looking ahead, after Christmas, Dave Ragsdale will expound on the changing face of insecticides. Scientists are finding new insecticides that are more narrowly focused to target specific pests. The general purpose, broad specturm, ecologically harmful insecticides may one day be a thing of the past.
Pete Moe will write about a day in the life of the Arb in February. In the future, you'll also get to meet Dr. Tim Kurtti, who does deer tick research.
Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.
Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab.
Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.
If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771.
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