By Jan Cashman


Why should I care about noxious weeds?

Driving through our beautiful state, especially in Western Montana, you can easily see the impact of noxious weeds.

There are large stands of the deceivingly pretty pinkish-purple flowers of spotted knapweed. All of these noxious, invasive weeds choke out native plants, reduce the natural variety of plants in that area, make areas more susceptible to fire, and reduce productivity in agriculture by invading range and cropland. The expense to us and our government to control these noxious weeds runs to the billions of dollars.

What is a noxious weed?

A noxious weed is a plant that is “competitive, persistent and harmful.” Most invasive noxious plants have been introduced—are not native to the area; most come from Europe and Asia. Therefore, they do not have natural enemies to limit their spread.

Categories of noxious weeds:

The state of Montana has ranked noxious weeds according to their prevalence in our state. Those ranked 1A and 1B have limited or no presence here. The 2A category weeds are present only in certain areas of the state. Those ranked 2B pose a serious threat, containing familiar, dreaded names such as leafy spurge, Canadian thistle, and spotted knapweed. There is another category, “3”, whose plants, such as Russian olive trees, have the potential for negative impact.


Canadian Thistle

Field Bindweed

Leafy Spurge


Russian Knapweed

Spotted Knapweed

Are some noxious weeds worse than others?

Difficult to control spotted knapweed is probably the most widespread and invasive weed in the state, especially in Western Montana. In 1920 knapweed was found in one county in Montana; today it is found in every county and infests about 4.5 million acres. Each knapweed plant produces thousands of seeds that live over 8 years after landing on the ground. Its long taproot makes it difficult to pull.

What can I do to control noxious weeds?

The best way to control a noxious weed is to limit weed seed dispersal by vehicles, clothing and animals. If the weed is found on your property, remove it before it becomes established. Then, if weeds have become established, the following methods of control are recommended:

  1. Herbicide-use the proper herbicide. Multiple sprays may be necessary.
  2. Mechanical means such as simply pulling works for small areas. Be aware that some weeds are strengthened by pulling if some of the root is left in the ground so be sure to get all the taproot. Wear gloves.
  3. Biological control– introducing insects that are a natural predator of the weed. Biological control can take a long time to eradicate the weed—sometimes years.
  4. Reseeding with desirable plant species, usually grasses, that will compete with the weed.
  5. Grazing, most often with sheep or goats.
  6. There are other controls for noxious weeds such as mowing (before flowering), tilling, or burning. However, not all weeds respond to these methods.


It is against the law to permit a noxious weed to exist on your property. But whether it is a law or not, it is to everyone’s benefit if landowners control the noxious weeds on their property, whether big or small infestations.

By Jan Cashman

Deer do more damage to our customers’ trees, shrubs, and flowers than any other disease or physiological problem. Besides selling your house and moving to the middle of town, what can you do to keep the deer from eating all your plants? Even homes on the outskirts of town with other houses around are affected. The deer feed at night; you probably never see them; you just see the damage they do to your plants. They seem to do the most damage in the fall when their other food supplies diminish. And, bucks rub their horns on the bark of young trees in the fall, doing considerable damage, even killing the tree.

Commercial Repellents

Several repellents are sold which are supposed to keep deer from eating the plant when sprayed on its leaves. Plant Skydd and Liquid Fence are two brands we sell. Reapply frequently. Try switching brands often so they don’t get used to one.

Household Remedies

Tie bars of strong smelling soap such as Irish Spring in the branches of your trees. Be sure to protect young fruit trees, a favorite of deer. Sprinkle blood meal around your flower bed or garden to deter deer and it will add Nitrogen to your soil. Again, reapply often. Net bags filled with human hair will repel deer. So will hot pepper sauce. Or plant garlic around the plants you want to protect. When one method seems to be losing effectiveness, try another.

Deer-Proof Plants

No plant is totally deer proof. If the deer are hungry enough, they will eat anything. However, deer do prefer some plants to others.

Other Solutions

Motion-activated yard lights might help keep the deer away. Dogs can help, too.


The only sure way to keep deer away from your plants is to fence them. A fence around your whole yard, tall enough so the deer can’t jump over it, is one way to fence. Or fence each tree you want to protect individually with 5 or 6 foot fencing. Wrap the trunks of young trees to protect them from bucks rubbing on them.


Young fruit trees, mountain ash, junipers, and maples are some of the trees that need to have their trunks protected from voles, tailless mice that live under the snow and feed on their bark. Poisons are also available. Tree wraps will help protect from rabbits, too.

by Jan Cashman

This is the time of the year when we often get asked “What’s wrong with my tree?” Many of the answers to this question are the same year after year. But occasionally a new insect or diseases finds its way to our valley.

Last year was the first year we saw the cottony psyllid insect, which is infecting the leaves of black ash (Fall Gold Ash). This year this insect is even more prevalent, especially on drought-stressed trees. In the spring the young psyllids, which resemble aphids, hatch and suck sap from the new leaves which shrivel and discolor. They produce a white, cottony material as protection. If not controlled, they can severely weaken the tree.

Insecticidal soap is an organic control that will kill the cottony psyllid on contact. Malathion insecticide, also a contact killer, is an effective chemical control. There are a couple of systemic insecticides which make the plant poisonous to the insect and also kill on contact. Bayer Tree and Shrub Insect Control (active ingredient:Imidacloprid) is a systemic insecticide that is mixed with water and poured under the tree so the roots take it up. The systemic insecticide spray, acephate, once called Isotox, also works on the cottony psyllid.

An abundance of aphids emerged earlier than usual this year, right after the warm spell we had in May, even on plants that don’t normally get aphids. Aphids are small (1/16”) soft-bodied insects that cause new leaves on a plant to yellow, curl and distort. They reproduce quickly and weaken the plant by sucking its juices, excrete a sticky “honeydew”, and can spread viruses. The controls for aphids are much the same as for the cottony psyllid above but do not use acephate systemic insecticides on any plant with edible parts or fruit. Environmentally friendly lady bugs can be released to eat aphids.

Spider mites continue to be a problem during our hot summers, especially on junipers, arborvitae, spruce, potentilla, and raspberries. This tiny insect sucks the sap from the needles or leaves of the plant, giving them a dull appearance. To detect the almost microscopic spider mites, look for grayish, pale needles, small webs, or shake a branch over a piece of white paper and look closely for movement of the tiny mites. Malathion or isotox spray should eliminate spider mites. More than one application may be necessary.

Scale is a large group of insects that harm many ornamental plants. Hard (armored) scale on the branches looks like brown bumps. Soft pine needle scale looks like small white specks on the needles. A severe infestation of scale can kill the branch. The dense branches of cotoneaster hedges are a place we see scale. If your hedge is severely infected, you might need to cut it down to the ground, destroy the infected branches, and let it grow back. Because of the waxy covering surrounding them, contact insecticides do not kill scale. Dormant oil spray is effective in early spring before the tree leafs out to smother the scales. Or use a systemic insecticide.

If you have spent any time in our national forests recently, you may have seen the spruce budworm outbreak on Douglas fir. Budworms, really not a worm but a caterpillar, will also eat the new needles of spruce in your yard. While still in the caterpillar stage, they can be killed with BT (Bacillus thuringiensis), a specific bacterial spray toxic to caterpillars but not other insects. Spruce budworm is often confused with white pine weevil, which kills the leaders of spruce in this area. They are different insects.

Tent caterpillars, which eat the leaves of our trees, are back this year. Pick the tents off and destroy them when the caterpillars are still contained. BT works on tent caterpillars, also.

Other insects which damage trees in this area include the aspen borer, bronze birch borer, and leaf miners. The last couple of years, windblown poplar budgall mites have damaged Canadian poplars. Harmful fungi such as Verticillium wilt, cedar apple rust, black knot, and black spot, can cause tree problems, some severe.

Fireblight is a serious bacterial disease that primarily strikes apples, but also can afflict mountain ash, cotoneaster, pears, and hawthorn. Prune out infected branches and plant varieties resistant to fireblight. Pseudomonas is another bacterial blight that produces similar symptoms in lilacs. Prune it out and allow adequate space between plants for air circulation.

Soil deficiencies can be the cause of tree problems. In this part of Montana, we see yellowing of leaves between the veins of mountain ash, plums, shrub roses, ginnala maples and even aspens because of iron deficiency (iron chlorosis). The plants are unable to absorb enough iron and other trace elements from our alkaline soils. Either acidify your soil or add chelated iron. If your soil has an extremely high pH, do not plant hydrangea, mountain ash, or other plants that need acid soil.

Too much TLC – by overwatering or overfertiziling – could be the cause of trees’ problems. The symptoms of overwatering often mimic those of underwatering—small, yellow leaves that wilt or drop. Roots can become waterlogged when trees are planted within a sprinkler system in heavy clay soils. Even wetter conditions are created when the tree is surrounded by weed barrier fabric and mulch. Be observant and use common sense when watering trees and shrubs in your yard. After a deep watering, let the roots dry out so air can reach them. Probe the soil to check moisture levels. You may need to reset your sprinkler system and/or remove the fabric.

Most of the time, trees should get all the nutrients they need from your soil. We advise against fertilizing young trees because of the danger of overdoing it. If you choose to use fertilizer spikes on your trees in the spring, they should be pounded into the ground at least 2 feet from the trunk of the tree. Never use more than the recommended dosage, and never fertilize trees after July 1.

Some tree maladies have been around for years, some are new to our area. Some need treatments, some are just cosmetic. Regardless, remember: insects and diseases prey on weak trees. Your best defense against insects and diseases is to keep your trees healthy.

Related Information:

by Jan Cashman

This spring, many deciduous trees in Bozeman are not leafing out.  We were hoping the trees were just slow because of our extremely late spring.  But now it appears some of the green ash, especially the commonly planted cultivar of green ash called ‘Patmore’, and other deciduous trees, including quaking aspens, cottonwoods, maples, plums, and cherry trees, may not survive.

Although we don’t know for sure what happened to these trees, we blame it on last fall’s weather.  In late September, 2009, we had 5 days in a row over 80 degrees, some of them over 90.  Then, in October it turned bitter cold, down to 9 degrees on October 12, setting a record low.  The ground froze quickly, leaving acres of potatoes frozen in the ground and unusable in the Churchill area.  Similar weather conditions occurred in 1983, with similar potato and tree damage, mostly of green ash trees.   Because of the fast temperature drop in October, the trees were not “hardened off” gradually, as they would be most years.  The leaves didn’t go through the normal process of changing color to yellow and orange and reds, but turned brown and hung on the branches.

This tree loss is frustrating because many of the damaged trees were reaching mature sizes with trunks from 3 to 6 inches in diameter.  It is also frustrating that green ash was the tree that was injured the most.  Why were green ash hurt so badly when it has always been touted as one of our hardiest shade trees, tolerant of cold, drought and alkaline soils?  When asked this question, Gary Strobel, doctor of plant pathology, said it is difficult to answer because we are dealing with complex biochemistry and plant physiology, dictated by the environmental factors.

So, there are no simple answers to how we can keep this from happening again, but here are a few suggestions:

  1. Don’t give up on your trees too soon. If the branches or buds show any life at all, there still might be a chance they will leaf out and survive.  The telling factor will be if they are strong enough to make it through next winter.
  2. After the 1983 tree injury in Bozeman, Orville McCarver, long-time MSU extension horticulturalist, suggested that the trees hurt the worst were overwatered in the late summer and fall.  Starting in July, to prepare trees for dormancy, (harden off), decrease watering.  This is not always easy to do if your trees are planted in a lawn area where you want the grass to stay green into September.   If possible, plant shade trees on the perimeter of your yard where they are not under your sprinkler system.  Or, at least, decrease the amount and frequency of water to your grass in mid to late summer.  Grass does not need as much water in late summer and fall when the nights are cooler and the days shorter.
  3. To discourage late summer growth, don’t fertilize trees after July 1.
  4. Planting only native trees is not the answer; even some quaking aspens around our area show damage this spring.  New varieties of trees are not always the answer either.   Newly introduced trees are not necessarily bred for their winter hardiness, but for other desirable characteristics like denseness, shape, or leaf color, therefore, the new selection may not be as winter hardy as the original tree.  But, the green ash cultivar called ‘Prairie Spire’, discovered in Rugby, North Dakota, appears to be a hardier green ash than the Patmore.  And, we recently heard about a new, disease resistant elm, called ‘Lewis and Clark’, discovered in cold, windy, Cooperstown, North Dakota.  When it is released to the public, ‘Lewis and Clark’ elm hopefully will prove to be a hardy shade tree for our area.
  5. City foresters know the danger of planting too many of one type of tree; 40 to 50 years ago, Dutch elm disease almost wiped out the most common shade tree in the Midwest, the American elm.  For a uniform look along its streets, many subdivisions in Belgrade and Bozeman required Patmore green ash to be planted on homeowners’ boulevards.  No one could predict that so many of these trees, some of them mature, would be injured or killed.

So the answer is to plant a diversity of trees, to prevent death of one kind tree from a specific disease, insect, or bad winter.  Depending on where you live, chose from elms, lindens, honeylocust, maples, oaks, cottonless cottonwoods, mountain ash, or Ohio buckeye, and don’t discount hardy green ash selections like ‘Prairie Spire’, for a variety of beautiful shade trees in your yard

Pine trees, particularly lodgepole pines, in the forest surrounding the Gallatin Valley have been hit hard with Moutain Pine Beetle the last few years. Then, during the summer of 2008, these beetles infected many of the pines in people’s yards in the valley—Scotch and ponderosa pines, especially.


If the pine trees in your yard are not yet infected:

  1. Install Verbenone Mountain Pine Beetle repellants on the trunk of your pines (2 packets per tree) in June before the next stage of the insect hatches.
  2. Spray with a concentration of 2% Sevin (Carboryl) insecticide in June, completely soaking trees that do not yet have the beetle.
  3. Burn the wood of any dead trees or strip its bark before June to prevent the insect hatching and spreading more.
  4. Cashman Nursery has information & supplies available for controlling the Mountain Pine Beetle. You may also contact Jeff Pfiel from Bozeman Tree Service.

Cashman Nursery has both Verbenone repellants and Sevin for sale – We welcome you to visit us at the nursery, or contact us at (406) 587-3406 for any questions you may have!

by Jan Cashman – 2009

Most of you have heard about the Mountain Pine Beetle, the insect that is killing many of the pines in Southwest Montana.   If the pine trees in your yard are not infected yet, you may have a chance to save them by installing Verbenone repellent pouches in the trees and/or spraying them with the chemical Sevin in June.  But, if you, like many of us in the Gallatin Valley, have already lost pines to the mountain pine beetle, your quandary now is what to plant to replace those trees.

You are replacing a pine, an evergreen, which you probably planted in that spot because you wanted the qualities of most evergreens—green all year, tall and fast growing, providing screening both summer and winter.  Our best selling evergreen is Colorado spruce (Picea pungens).  Only in rare instances have spruce trees been susceptible to the pine beetle.  Although slower growing than most pines, Colorado spruce is a tree well-suited to our area.  Colorado spruce is denser than pines and its bluish short needles seldom winter burn.

Black Hills Spruce (Picea glauca densata) is another easy-to-grow spruce that is not quite as tall at maturity as the Colorado.   We like it for its deep green needles, its denseness and its perfect Christmas tree shape.  Similar in height to the Black Hills spruce is the native Engelmann spruce, another evergreen option.

My husband, Jerry’s first suggestion for a tree to replace dead pines was larch (Larix).   Native to western Montana, larch are tall and narrow conifers which lose their needles in the fall.  If you have visited Western Montana in October, you have seen the tall, pyramidal trees on north slopes turning a beautiful, golden color.  Then, the needles drop.  Although not native here in the Gallatin Valley, the larch we planted in our yard has grown quickly and well.  And, of course, winter burn is not an issue because its needles are not present in the winter to burn.

Firs are another evergreen that you could plant to replace pines.  Our surrounding mountains are full of tall Douglas fir (Pseudotsuga menziesii).  Or plant the beautiful Concolor fir (Abies concolor), which has long bluish-green needles.  (If you live in a windy, open area with heavy soil, Concolor fir may not be the best choice for you. It could winter burn.)

Nancy Berg, who works here at the nursery, suggests planting hardwood trees such as maple, oak, or linden as replacements.   She feels that the slower-growing, longer-lived hardwoods provide years of beauty and satisfaction compared to shorter-lived, soft-wooded aspens, cottonwoods, and chokecherries.

Many experts are suggesting replanting with the same pine variety you had to remove.  If this sounds risky to you, remember that serious pine beetle outbreaks occur only every 30-35 years or so, the beetles prefer mature trees to smaller ones, and it is hard to find a tree that is not plagued by some insect or disease.   So, if a Scotch or ponderosa pine was the tree you wanted for that spot, don’t be afraid to replant one there.  (To be one the safe side, I would wait a few years until this outbreak runs its course.)

There are many other trees that can be planted to replace lost pines.  Mountain pine beetle does not live in the soil, so you can replant a tree in the same spot without risk of re-infection.  Flowering and ornamental trees such as flowering crabs and Japanese tree lilacs are beautiful.  Or, plant something fruiting like an apple or cherry tree to feed your family.  But, for the sake of Bozeman’s urban forest, do replant.

by Jan Cashman

We, along with many of you, have deer and voles in our yard and garden. Both are destructive to plants. There is no easy solution to keep them away from plants we value. But there are ways to lessen their damage.

VOLES, also called meadow or field mice, are rodents with stocky bodies and short tails. They are found where there is a dense ground cover of grasses, plants, or litter. In the fall, they move into our yards and gardens from adjoining fields as their food source decreases. One to two inch holes in the ground mark the openings of their underground tunnel systems. You can see their runways above ground, too, where the grass has been eaten. Voles do much of their damage under the snow in the winter, gnawing the bark of trees and shrubs, especially spreading junipers and young fruit trees. If they girdle the bark through the cambium layer, the tree will likely die above the girdling.

There is no simple and sure way to get rid of the voles in your yard. Vole populations fluctuate in 2 to 5 year cycles. The last few years have seen a lot of them. An old-fashioned, hard winter might reduce their numbers.

When voles moved back into the perennial garden near our house in August, we tried trapping them, using peanut butter for bait. I put the traps in their runways where the grass meets the flower bed. In one week I had trapped 13, but after that, even though I still see voles there, I haven’t caught any more. Cats make good vole catchers. Some dogs will catch them, too.

Voles like tall grass so keep your lawn mowed short, especially the last mowing in the fall. Rake leaves and litter from under trees which will also help eliminate harmful insects that might overwinter there. Wrap fruit trees in the fall with a wrap voles cannot chew through. Make sure the wrap goes below the soil level so none of the bark next to the ground is exposed. At their worst, voles tunnel in the soft soil under a tree and destroy its root system.

Repellents are available which provide short term protection from voles, but need to be reapplied often. Poison baits containing zinc phosphide work but need to be kept away from birds and pets that might eat the bait. We put the poison bait in a 2″ PVC pipe that the voles can run through but bigger animals cannot. Although most poisoned voles die below ground, a dead vole could be a risk to other animals and birds that might eat them.

To discourage DEER from eating your plants, the only sure solution is a 6 foot fence around individual trees or your whole yard. But, there are other solutions that can make a difference:

There is a long list of annuals, perennials, shrubs and trees that are “deer resistant” plant them in your gardens . Deer don’t touch my allysum, marigolds, snapdragons, zinnias, monkshhod, artemesias, bleeding heart, echinacea, foxglove, catmint, peony, poppies, rudbeckia, salvias, and Russian sage. They avoid herbs and ornamental grasses. Deer love to nibble on tulips, but they won’t touch daffodils. They also stay away from allium, a hardy and interesting perennial planted from a bulb in the onion family.

Deer don’t usually eat spruce and firs. Junipers are not their favorite, although the native junipers west of Butte have been eaten as far up as the deer can reach. Arborvitaes are one of their favorite foods; we have to fence ours every fall and keep them fenced till spring or deer will eat all their foliage. Deer also like to eat Scotch and Austrian pines, but usually avoid ponderosa and lodgepoles. If you live in a high deer area, fence your mountain ash, maples, and fruit trees against them.

Roses, even though they are thorny, are a favorite food of deer. Barberry, caragana, honeysuckle, lilac, potentilla, ninebark, and viburnums are shrubs less favored by them.

The foul smell and taste of commercial repellents keep deer away, but reapply often, especially after precipitation. Other household remedies can deter deer. I have sprinkled blood meal around my tulips when they first come up in the spring which seems to stop the deer from nipping the fresh new leaves of the bulbs. Some homeowners hang bars of strong-smelling soap or net bags of human hair in their trees to deter the deer.

Fall is a bad time for deer damage, when the bucks rub their antlers on tree trunks, so wrap young trees before this happens.

Gardening in Montana can be a challenge. Between the weather, the deer, rodents, weeds, and insects, it is amazing we get anything to grow. But if you use the right plants and are diligent with protection, you can conquer these adversaries and have a beautiful garden.