MSU Extension Service Resource For Trees, Shrubs, Chestnuts, Pruning and Related Links

  • Montana Forestry Newsletter
  • Montana Conservation Seedling Nursery - Order Form & Available Seedlings
  • Trees and Shrubs in Montana
  • Recognizing Tree Hazards
  • Fall Conifer Needle Loss
  • Blue spruce are being attacked by a fungus disease called Cytospora canker
  • Pruning Fruit Trees
  • Pruning Deciduous Trees
  • Tree Injection and Implant as a Conservation Tool
  • When should I prune my apple trees?
  • Autumn Olive - More than Just Another Pretty Plant

    Robert Gough, PhD, Montana State University Extension Horticulture Specialist

    It seems all of us are trying to eat more healthy foods. And now researchers are even looking into the benefits of ornamental plants. The autumn olive, a close relative of our Russian olive, produces brightly colored red berries--unlike the Russian olive's drab fruit. Native to southern Europe and western and central Asia, autumn olive was introduced into the U.S. in 1830 as an ornamental plant. It attracts wildlife, reduces erosion and fixes nitrogen into the soil. Now USDA scientists have found another benefit.

    In the October 2001 issue of HortScience, scientists reported that the fruit of the autumn olive contains several carotenoid pigments widely believed to protect the human body against heart attack and various forms of cancer. The predominant pigment was lycopene. Tomatoes, a much-celebrated dietary source for this important pigment, provide about 3mg of lycopene per 100g of the fruit. The berries of the autumn olive contain between five and 15 times that amount per 100g. The researchers suggested that this discovery could lead to the inclusion of autumn olive in our diets. The bad news is that the species is not particularly hardy in Montana.

    Are horse chestnuts edible?

    No. They're so bitter and astringent who would want to eat them? They can be deadly too. Children have died after eating the shiny nuts, and powdered nuts and mashed branches dropped into ponds have killed fish. The toxin is probably the glycoside aesculin. Symptoms of poisoning include nervous twitching, weakness, lack of coordination, dilated pupils, vomiting, diarrhea, depression, paralysis and stupor. The tree (Aesculus hippocastanum) is a native of southern Asia and was introduced as an ornamental into this country from Europe about 1750. Since then it has spread so widely that today it's almost considered native. In winter the tips of the up-curved branches bear glistening buds that look tipped with varnish. These open in spring into showy spires of white blossoms tinged with red and yellow stamens. But in autumn the spiny seed burrs litter the ground, making walking barefoot beneath this messy ornamental a hazardous proposition. A number of attractive cultivars have been developed, some having double flowers, variegated leaves and re-tinted blossoms. They all produce the poisonous nuts. As with any plant, be sure you've identified it as being edible BEFORE you eat it.

  • Can tree roots be damaged by our winters?

    We all know that the tops of trees sometimes suffer winter damage. But how about the roots? A tree's roots make up at least half of the plant, but no one talks about them much. Root damage in winter is fairly common where winter precipitation is light and the temperatures are cold. It is usually worse in light, dry soils where there is little snow cover. If the roots are damaged, the plant may begin to grow normally in spring. It may send out new shoots and bloom, perhaps even set fruit, then die suddenly as soon as the weather turns hot and dry.

    If only part of the root system is damaged, the tree will be slow in sending out spring shoot growth. This condition may last for several years or until the top and the bottom of the plant re-establish their balance.

    What are the critical temperatures for root damage? It varies by species and root type. Fine roots of ash are killed at a soil temperature of 7 degrees F and those of other hardy plants at 5 to 14 degrees. Apple roots die when exposed to winter soil temperatures of about 10 degrees.

    Root killing is most frequent near the tree collar where roots are closest to the surface.

    So what should you do for protection? If the snow in your area doesn't get deep enough to provide insulation, a fluffy organic mulch, such as at least 4 inches of wood chips or pine needles, placed over the soil beneath the drip line should provide ample protection.

  • How much fertilizer should I give the trees in my yard?

    How much you fertilize your trees, or even if you do, is open to debate. If your trees are mature and healthy, don't fertilize them. If they are young and actively growing, or if they appear stunted and the leaves discolored, they may need fertilizing. Check with your county's MSU Extension agent to be sure.

    Tree growth is most often limited by a nitrogen deficiency. Therefore, use a complete fertilizer high in nitrogen, such as 10-5-5, 10-6-4 or even 10-10-10, and apply it to the entire area beneath the branch spread of the tree.

    Measure the diameter of the tree's trunk about 4 feet above the soil line. For trees less than 6 inches in trunk diameter, apply 1 pound of fertilizer annually for each inch of trunk diameter. For trees more than 6 inches in diameter, apply 2 pounds of fertilizer for each inch of trunk diameter.

    Apply the fertilizer in early spring as soon as the ground has thawed. DO NOT fertilize your trees after Father's Day.

  • Mildew in Flowering Crabapples

    Jack Riesselman, Plant Diseases

    Recent samples and reports from central Montana reveals that a severe outbreak of powdery mildew is underway in crabapples. This is not just a light infection that is causing slight leaf discoloration. In this case, newly expanding terminals are severely blighted and in some cases, dead, as a result of the infection.

    In my 20 years here I've not seen another instance where mildew has caused such significant damage on trees. Its our belief, that because of the mild winter, the fungus which invaded the leaf buds last fall was able to survive until this spring giving it a jump on the trees.

    Normally we don't recommend control for powdery mildew in Montana. However, in this case I believe it would be beneficial for infected trees to be sprayed. If temperatures remain below 80 F you can use any of the sulfur products available locally. If the condition continues to worsen an application of Benlate or Topsin M, may give the best results.

  • Is fall watering the right thing to do in Montana?

    Do not water your trees and shrubs now unless they are suffering from severe drought. Instead, let them struggle a bit. Put them under stress so the soft shoots will become woody and harden before winter. When the leaves on deciduous trees have turned color and begun to drop, then is the right time to apply water enough to keep the root zone soil moist. The feeder root zone of most of our trees and shrubs extends about 8 to 12 inches into the soil.

  • What is topping?

    I believe the sense of the word you are referring to is the removal of a large portion of the top of a tree, leaving only stubs on the main trunk or lateral branches. Other names for this include "dehorning," "heading" and "tipping." The latter two terms also refer to legitimate practices that are much less severe than "topping." The most common reason given for topping is to reduce the tree's height to reduce the chance of it falling over. Topping is an old practice that was shown to be harmful nearly 50 years ago. Instead of reducing a hazard, it can actually increase the hazard to pedestrians and structures.

    Here's how: Topped trees often lose from 50 percent to 100 percent of their leaf surface. In an effort to regain its food-making capacity, the tree releases blind buds from their dormancy and makes irregular shoot buds in the wound tissue around the cut. Both types of buds send out vigorous shoots that give the tree a "broomy" appearance. Not only do they make the tree look ridiculous but they are poorly anchored, weak and often break off. The stress makes the tree more prone to attack by insects and diseases. The large, open pruning wounds are ripe for attack and the tree may lack enough energy to chemically defend itself. Furthermore, topping cuts made along a trunk or large branch are sometimes unable to close properly, leaving them open to decay. The decay organisms can then move down the trunk or branch and topple the tree. But wait, there's more! Removing the upper branches exposes the remaining branches to sunburn. This damages the bark and can lead to infection, bark splitting, cankers and dead branches.

    Topped trees are expensive, and a potential liability. Because of their broomy growth they have to be pruned fairly regularly. If they die, they have to be removed. On the other hand, healthy well-kept trees can increase your property value by 10 percent to 20 percent. There are right ways to reduce the size of a large tree (within reason). Hire someone that knows how to do it, without topping, and realize that sometimes there is no good way to deal with an overgrown tree short of removing it. It was the wrong tree for the location.

  • Do yellow chokecherries exist and will they grow in Montana?

    The "regular" chokecherry, Prunus virginiana, introduced into cultivation in 1724, produces the deep red or purple fruit with which we are all familiar. Prunus virginiana leucocarpa, introduced into cultivation in 1889, produces amber-colored fruit and Prunus virginiana xanthocarpa produces yellow fruit. It was first cultivated in 1912. If you like chokecherries and would like to try something different, try planting one or two of the yellow-fruited varieties.

  • Q: I have several broken branches on trees in my yard caused by recent storms. What can I do about them?

    The right recommendation will depend upon size of the tree, the size of the branch, and the owner's ability to do the work. But here are a few things to think about. For large or small branches that have broken off completely, trim up the wound that is left, cutting back to a side branch or to the branch collar of the broken branch. "Large" is a vague term, but let's call it anything larger than 3-4 inches in diameter at its base. If you have a large branch that has broken but remains attached to the tree, remove the branch as described in the above example. Large branches that are propped back into place seldom heal and regain enough strength to hold them permanently. They then become an accident waiting to happen once you've parked your car beneath them. Small branches that are broken but still attached to the tree can be propped back into place, getting as tight a fit as possible. Trim off loose bark and coat the wound with tree wound dressing, then splint the wounded area by bolting boards over it and into the sound wood on either side. We don't generally recommend wound dressing when removing branches, but in this case you need to keep the cambium from drying out, so we treat this more as we would a graft. It's the cambium that makes the callus tissue heal the wound and knit the branch pieces together. Be advised that this procedure has only an even chance of working. If you did not discover the damage immediately and the wound tissue dried out before you could graft it together, or if temperatures got very cold right after the damage occurred, the procedure probably will not work and you'll have to remove the broken tissue.

  • Q: How large a root ball should I take with a tree or shrub I want to transplant?

    By: Bob Gough, MSU Extension Horticulture Specialist

    Ideally, you should take as large a root ball as you can move. And that may not be all that large since soil can get pretty heavy. Here are some rules of thumb to follow. We recommend that a root ball less than 20 inches in diameter needs to have a depth at least 75 percent of the diameter. If the diameter is 18 inches, then the depth of the ball needs to be at least 13.5 inches. The depth of root balls between 21 and 30 inches in diameter should be at least 66 percent of the diameter and root balls between 31 and 48 inches in diameter need to be 60 percent as deep as the diameter. To calculate the weight of the root ball in pounds, take one third of the product of the square of the diameter times the ball depth and multiply that number by 0.075. Then what is the approximate weight for a ball 18 inches in diameter? [(182 x 13.5) / 3] x 0.075. The answer is 109.35 pounds.

    Now, are there minimum sizes of root balls for the size of the tree? Use the rule of thumb of having at least a 1-foot diameter ball for every 1 inch of trunk diameter. Plugging these numbers into the example above, a tree with a trunk diameter of 1.5 inches, if dug properly, will have a root ball weighing over a hundred pounds.

    Many lawn and garden publications are available at local MSU Extension offices. In Lewistown, call 538-3919 or 538-7611, or stop by the office at 712 West Main.

  • Q: When should I prune my apple trees?

    Any time from now until the buds begin to swell. It is easier to see their framework now and more pleasant to work in the cool weather. You won't knock off any swollen buds or young fruit and the wounds will heal quickly. Make sure your tools are sharp and make all cuts to a side branch or to a bud. Never leave a stub-which would take a long time to heal, if it heals at all.

  • Why do evergreens turn brown?

    By: Bob Gough, MSU Extension Horticulture Specialist

    Some needle browning on your conifers (especially toward fall) is natural and nothing to be concerned about. Older, inner needles of evergreens do discolor and drop after a few years. Just how long they last depends upon the species. Scotch and Ponderosa pines usually keep their needles for three years, then replace them with new. Red pine needles last for four years. Spruce needles last for several years then finally turn yellow and fall, to be replaced with new needles. Arborvitae needles usually last a long time, longer than pine needles, but then they too turn brown, rather than yellow, and fall.

    Conifer needles lose moisture throughout the winter and can't replace it from frozen soil, so it's normal for some needles to turn brown and drop.

    On the windward side of the tree or on the side where the afternoon sun is hottest, windburn or sunscorch is common in our region. There's not much you can do about it. If the needles are brown but flexible, they may color up eventually -- if they're brown and brittle, they're done for.

    Want to know more about conifers? Contact your Fergus County MSU Extension office or visit

  • Helpful Disease Diagnostic Websites & References:

    • General: 
      • (crop disease, insects, weeds) 
      • Missoula: 
      • Colorado State Extension:; fact sheets 
      • University of Nebraska: =subjectAreasD&subjectAreasId=28 
      • North Dakota State University: 
      • Oregon State: 
      • Good pictures: , 
      • Crop-specific books: APS compendia: series.html (they also sell cool videos of pathogens infecting plants for teaching  purposes – see clips online)
    • Turf: 
      • Corwin, Tisserat and Fresenburg. Identification and Management of Turfgrass Diseases. (free pdf or order  for $3) 
      • Cranshaw, W. 2004. Insect Management Recommendations for Turf and Ornamentals,  $15.95    Home use pesticide database (not necessarily current, unfortunately):
    • Trees:
      • Colorado State University Cooperative Extension Service. 2000. Insects and Diseases of  Woody Plants of the Central Rockies. Bulletin 506. 284 pp. W. R. Jacobi, Co editor.  [this is currently being revised] Order online, $40 
      • SDSU Tree Pest Alert: information/Pest-Alert-Archives.htm 
      • Western Foliage Diseases (note: most conifer problems we see in the lab are not caused  by a disease) 
    • Vegetables: 
      • Cornell: 
      • MSU plant pest identification through the Schutter Diagnostic Lab:
    • Submitting Plant Disease Specimens:

      Extension Agents: please use the Plant Diagnostic Information System (PDIS),, to submit specimen information and remember to send the specimen with a print out of the sample summary. Please read the directions ( for PDIS submission and/or watch the video ( If you have any questions about PDIS, please contact Kara Schile,, (406) 994-5150.

      1. Send in whole plants with roots whenever possible.
      2. Collect samples with mild, moderate, and severe symptoms as well as a healthy comparison.
      3. Keep some soil around the root ball; wrap this in plastic and secure with rubber band around the base of the plant. Loosely enclose the foliage in plastic or paper.
      4. Try to package samples so that when they arrive in the Clinic, we could repot them and have the plants survive!
      5. Try to keep sample as fresh as possible until you can get it to the county agent: refrigerate if possible.
      6. Include photographs or videotapes illustrating the problem if possible.
      7. Mail to: Schutter Diagnostic Lab, P.O. Box 173150, Bozeman, MT 59717-3150. Please mail a copy of the PDIS Summary with the sample.

      Please include background information. Plant problems often are influenced by many different factors, so include as much information as possible:

      • Plant and variety
      • Irrigated or dryland
      • Soil type
      • Crop history
      • Seeding date, rate, and row spacing
      • Chemicals used with names, rates, and dates
      • Rainfall, temperature extremes, heavy winds
      • Pattern of symptoms in the field
      • Previous problems in the field
    • Mushroom Diagnostics—Questions to ask clients:

      Please be as accurate as possible in filling out Mushroom Specimen ID Form 212 ( parts 5 through 9. For accurate identification, it is important to know the habitat in which the mushrooms are growing. For example: some mushroom species only grow near poplar trees-these may be in a lawn growing on the roots of poplar trees, some may grow in a lodgepole pine forest, others may grow in a pasture- far from any trees.

      Please make sure you let us know your question. For example:

      • Is it edible
      • Is it poisonous
      • How do I get rid of it
      • What is it (curiosity)?
      Mushroom Submission:
      1. Please send at least 2 specimens for identification.
      2. Include the whole mushroom cap, stem and MOST IMPORTANTLY any underground structures.
      3. Submit fresh, average-sized specimens, not the largest or smallest ones.
      4. Wrap each specimen separately in wax paper or newspaper (newspaper has properties that reduce decay). Please DO NOT place specimens in plastic bags since this will hasten decay.
      5. DO NOT wrap different specimens together!
      6. Mail in a sturdy box. Please DO NOT mail in an envelope since this will squash the specimens.
      7. Write: Mushroom specimens-refrigerate immediately in large letters on the box.
      8. Mail to: Cathy Cripps, Dept. of Plant Sciences & Plant Pathology, P.O. Box 173150, Bozeman MT, 59717-3150. Remember to mail the form with the specimen.