Horticluture FAQ's

Are ants eating my plants?


No! Different species of ants have various food habits.  Some like sweet materials and others like seeds, grease or protein-rich foods.  Ants are common and tremendous numbers are found in the average yard.  Most ant activity is unobserved but considered useful in controlling pest insects, weed seeds, and improving soils by nest building.  Ants can cause a nuisance problem in unwanted areas.  Ants also are commonly associated with aphids and other honeydew producing insects.  The ants collect and feed on the sweet, sticky honeydew that these insects excrete. In turn, ants protect these pest insects from attack by lady beetles and other natural enemies.  Mixing boric acid with something sweet like honey or jelly mixed with peanut butter is a common bait to control ants

Are there poisonous spiders in Montana?

There is only one poisonous spider that in Western Montana that can present a danger in terms of their bite:  the Black Widow spider. 

How much do I need to water my trees and shrubs?

Water requirements are dictated by species, environment, site location, and type of irrigation. Exotic shade trees require an average of 30 to 40 inches of precipitation per year.  Yet the average annual precipitaiton for Missoula is around 14 inches.  Tree roots generally extend over twice the diameter of the crown.  80-90% of the water uptake happens in the fine root hairs in the top 30 inches of soil.  Water the entire area under the tree canopy and thoroughly soak to encourage the development of deep roots.  Water less frequently (weekly) for several hours.   Short, frequent watering may encourage shallow, surface roots.

Waterwise and native plant species generally require less supplemental water than introduced species once they have been established.  

What are the first and last frost free dates?

The average first frost free date for Missoula is May 19th, and the last average frost free date is September 27th.  This information is based upon thirty year averages from the Missoula International Airport, compiled by the National Climatic Data Center.  Click here for frost dates around the state.

What are the worms in my apples?

The worm inside your apple is the larvae of the coddling moth.  The codling moth caterpillar enters the flesh of apples and feeds inside the fruit.  Timing & repeat applications are necessary for control.  Check the pest alert hotline (258-3820) for timing and sprays

What is making the leaves curl on my trees?


Aphids are most likely the culprit.  The least toxic option is to spray with insecticidal soap or insecticidal soap plus neem.  There are also many naturally occuring insect predators and parasitoids.  Check the Plant Diagnostic Data Base for further information.

What zone are we in?

Zone 5, or if you are in an exposed area you may be in zone 4.  Check out the new interactive Plant Hardiness Map.

When should I prune my trees and shrubs?

Pruning is done to accomplish a number of different goals:  to control height or growth of the plant, to invigorate new growth, to enhance flower and fruit production, and to remove dead, diseased, or damaged tissue.  The timing of pruning depends on the goal wishing to acheive, the type of plant, and the time of year.  See Missoula County Horticulture Fact Sheet #7, Deciduous Pruning MontGuide, or Fruit Tree Pruning MontGuide for further guidance.