Fall Planting for Trees, Shrubs and Bulbs in Montana

Can you plant trees and shrubs in the fall in Montana?

Yes, with a caveat about watering. Utah State University Extension says trees are best planted while dormant in early to mid-spring after the soil has thawed, and that fall planting also works well for many species, though watering is critical if the fall is dry. Container and balled-and-burlapped stock are the usual choices in fall. USU says bare-root trees should only be planted in spring while still dormant.

Our own rule is that a plant needs warm soil for its roots to establish before winter dormancy, so late spring through early fall is the ideal stretch, and planting too late leaves roots with no time to settle in. That means early fall beats late fall. We have not found a reliable published cutoff date for Missoula or the Bitterroot, and it would vary by elevation and year, so treat the frost dates in our guide to frost dates in Missoula and the Bitterroot as a warning that the window is closing rather than a deadline.

What should wait until spring?

Bare-root stock, for the reason above. Plants that are marginally hardy for your site are also better planted in spring, so they get a full season of root growth before their first winter. The University of Minnesota Extension says to put marginally hardy plants in sheltered locations, and that newly planted trees are especially vulnerable to cold air reaching roots through cracks in the planting hole. Our guide to hardiness zones for Missoula and the Bitterroot can help you judge what counts as marginal.

Exposed sites deserve the same caution. If the planting spot is windy, south or west facing, and you cannot get water to it in winter, spring is the safer choice. Evergreens on those sites are the riskiest, because they keep losing water through their foliage all winter while the roots sit in frozen ground, a problem our guide to winter burn on evergreens explains. Our guide to the best trees to plant in western Montana helps with choosing species.

Is planting in fall different from planting in spring?

The method is the same. USU recommends a planting hole at least 2 to 3 times the width of the root ball and no deeper than the root collar, the point where the roots flare from the trunk. It warns that potted and burlapped trees often have the collar buried deep in the root ball, and planting that too deep can cause decay and girdling roots. Our step-by-step guide on how to plant a tree in Montana goes through it, including the call to Montana 811 first.

What changes in fall is the aftercare. Minnesota Extension says to check new plantings for cracks in the soil and fill them, because cold air through those cracks can kill new roots. It also says that plants in vigorous growth late in the fall are most likely to suffer winter dieback, and to avoid late-summer pruning, fertilizing and overwatering. So do not push a new plant with fertilizer in fall. MSU Extension's guide to transplant shock says pruning of new trees should be limited to diseased, damaged or dead limbs.

How much should I water a fall-planted tree or shrub?

Consistently until the ground freezes, then during dry spells. MSU Extension's north central Montana horticulture blog says the recommendation for trees and shrubs, especially conifers, is to water through the fall until the soil freezes. Its transplant shock guide says regular watering in the first year is crucial, and that woody ornamentals can take up to five years to establish depending on size.

Colorado State University Extension's fall and winter watering fact sheet gives figures for dry winters: water only when air and soil are above 40 degrees with no snow cover, at midday so water can soak in before night, about once or twice a month during extended dry periods. It suggests 10 gallons per inch of trunk diameter for trees and 5 gallons twice a month for a newly planted shrub, assuming mulch. Blow out the sprinklers in fall as usual, which means hand watering these plants. Our guide to winter watering for trees and shrubs covers Montana timing, and our sprinkler winterization service handles the system.

How should I protect a newly planted tree over winter?

Mulch the roots and guard the trunk. Minnesota Extension recommends 3 to 4 inches of shredded wood mulch over the roots of new trees and shrubs, pulled back about 6 inches from the trunk in a donut. It also recommends wrapping young, new and thin-barked trees with a white wrap to prevent sunscald, for at least two winters on new trees, putting it on in fall and removing it in spring after the last frost. It says not to use brown paper wrap or black guards, which absorb heat. MSU Extension similarly says wraps should come off when it warms in spring.

Animals are the other winter threat. Minnesota Extension describes cylinders of 1/4 inch hardware cloth set about 6 inches from the trunk, sunk 2 to 3 inches below ground for mice and reaching 18 to 24 inches above the expected snow line for rabbits. Our guides to deer browse and vole damage cover those pests, and our guide to protecting shrubs over winter covers screens and ties.

When should I plant tulips and other spring bulbs?

The most useful published guidance we found is from University of Nebraska Extension: plant spring-flowering bulbs in late September through October when soil temperatures fall below 60 degrees, which gives roots time to develop before the ground freezes. Nebraska is not western Montana, so use a soil thermometer and lean toward the earlier part of that range at higher elevations. If bulbs arrive early, Nebraska says to store them somewhere cool and dry, around 60 to 65 degrees.

If you are holding bulbs in November and can still dig, planting is usually a better bet than keeping them for another year, since Nebraska warns that extended storage in high temperatures can damage flower buds. There are no promises on first-year bloom, and October is the better target. Beds that get walked over or dug in spring should be marked so nobody plants on top of them.

How deep do bulbs go?

University of Nebraska's table lists these depths in inches: crocus and most small early bulbs about 3, common hyacinth 6, early and species tulips 6, mid and late-season tulips 8, miniature daffodils 5, and large daffodils 8. It says to plant 1 to 2 inches deeper than recommended in loose, sandy soil, to place the pointed end up, and to loosen a new bed at least 4 inches below planting depth. A well-drained soil is essential for bulb survival, it says, which makes a wet corner a poor choice however good the bulbs are.

After planting, water thoroughly and, without rain, water deeply once a week until the ground freezes. Once the ground has frozen, add a 2 to 3 inch layer of organic mulch such as wood chips, shredded bark or pine needles. Deer will eat tulips, and our guide to deer-resistant plants is worth reading before you buy; plant in groups, since Nebraska notes bulbs planted singly or in rows are not effective.

What other fall planting is worth doing?

Perennials can go in early in fall where they have time to root, and MSU says division in fall should be done early enough that new plants establish a root system before the ground freezes. Fleshy-rooted perennials such as peonies, Oriental poppies and daylilies are best divided in fall, according to its perennials guide. Our guide to spring garden bed prep picks up where this one stops.

Fall is also a good time to plan rather than plant. Note what did well and what struggled, and plan bigger projects while you can see the bones of the garden. If you are clearing a bed, our fall yard cleanup checklist covers what to do before snow. MSU's checklist also suggests leaf litter or straw over perennial beds in areas with limited snow cover, to insulate the roots of more sensitive plants.

Should I hire someone to plant in fall?

It helps if the plants are large, the soil is difficult, or you want the whole bed designed and installed together. We install trees, shrubs and plantings as part of our landscaping design work across Missoula and the Bitterroot Valley, and we will tell you plainly if it is too late in the season to plant what you have in mind. This guide is part of our Montana Landscaping, Lawn & Irrigation Guide. Call (406) 215-7319 or request a free estimate. If the fall has passed you by, we can plan it now and put it in the ground in spring.

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