How to Plant a Tree in Western Montana So It Survives

When is the best time to plant a tree in western Montana?

Spring and fall, and not the middle of summer. Montana State University Extension says nursery-grown plants transplant well in spring, before temperatures get too hot and the soil dries, and in fall, after the heat of summer has passed and while the soil is still warm. Bare root trees are the exception: MSU Extension says they should go in during early spring while they are still dormant.

The state nursery is more specific about spring. The Montana DNRC Conservation Seedling Nursery in Missoula describes early spring as the best time to plant in Montana because soil moisture is high and temperatures are cool, and it advises stopping if the day turns warm or windy. An MSU Extension guide to growing spruce adds two points worth knowing here: in fall, plant after the first hard frost while the soil is still warm, and do not plant during a chinook.

How wide and how deep should the hole be?

Wide and shallow. The International Society of Arboriculture (ISA) recommends a hole two to three times wider than the root ball but only as deep as the root ball. Utah State University Extension gives the same width, suggests sloping the sides, and explains why: most tree roots grow horizontally and stay fairly shallow, so the loosened soil belongs beside the tree, not under it.

Do not dig deeper and then refill. Utah State advises setting the root ball on undisturbed soil, because loosened soil at the bottom lets a heavy root ball settle and sink until the tree ends up too deep. If the sides of the hole come out smooth and glazed, which happens in the heavier valley soils, rough them up with the tip of the spade so root tips can get through. Before any of this, request a utility locate. Montana811 is a free service and digging a planting hole counts.

Where is the root flare, and why does it decide everything?

The root flare, also called the trunk flare or root collar, is where the trunk widens at its base and the first main roots head outward. ISA says the flare should be partially visible after the tree is planted. That sounds simple, and it is the step most often missed, because the flare is frequently hidden when the tree arrives.

Utah State Extension explains that most potted and balled and burlapped trees come out of nursery production with the root collar buried under extra soil. Plant one with the top of the root ball level with your yard and the collar ends up too deep, which can cause the buried trunk to decay and makes girdling roots more likely as the tree grows. The fix is to find the collar first, scrape off the excess soil on top of the root ball, and measure the hole depth from the collar down. Utah State suggests returning a tree whose collar is buried by more than a third of the root ball's depth.

How do you handle a container tree versus balled and burlapped?

With a container tree, the concern is circling roots. Pots can train roots to circle, and those roots can girdle the tree years later. Slide the tree out, look at the outside of the root mass, and straighten or cleanly cut roots that are wrapping around it. Lift and carry the tree by the root ball or the container, never by the trunk.

With a balled and burlapped tree, set it in the hole first and then take the packaging off. ISA says to remove any covering from around the root ball and trunk, and to remove the wire basket or cut off the top one or two rings so it sits low and cannot interfere with roots. Utah State Extension goes further and recommends removing twine, burlap and wire, backfilling as you go if the ball is loose, and slitting anything that has to stay. The MSU spruce guide makes the point that plastic burlap and wire do not decompose and should come off.

What goes back in the hole?

The soil that came out of it. Utah State Extension recommends backfilling with the original soil because that is the soil the roots must eventually grow into, and it advises against fertilizer of any kind at planting time. ISA says the same about fertilizer. Firm the soil gently by hand to remove air pockets and water as you fill. Do not put soil on top of the root ball.

Does a new tree need staking?

Usually not, though wind is a fair reason on open Bitterroot benches and exposed lots. ISA notes that studies show trees develop stronger trunks and roots when they are not staked, but that staking may be needed for bare root stock or on windy sites, and that stakes should come off after the first year of growth. Utah State says to use wide, soft strapping, attach it loosely enough that the stem can still move, and remove it within one or two years. A tie left on is one of the quiet ways a young tree gets strangled.

How much mulch, and how close to the trunk?

ISA recommends a 2 to 3 inch layer of mulch with a mulch-free gap of an inch or two at the base of the trunk, so the bark stays dry. Utah State suggests 3 to 4 inches of wood chips over a bed several feet wide, kept a couple of inches off the trunk to avoid decay and rodent damage. In a climate with hot, dry summers, a wide, flat ring of chips is the cheapest help a new tree can get.

How should you water in the first year?

More often than an established tree, and for longer than one season. Utah State Extension points out that up to 95 percent of a tree's roots can be cut off in transplanting, so water is its greatest need for the first year or two. ISA's baseline is at least once a week, barring rain, and more often in hot, windy weather. Check with your hand: soil below the surface should be moist enough to form a ball when squeezed. Overwatering in poorly drained soil is also possible.

MSU Extension stresses that even drought-tolerant natives need watering until they are established, which for trees can take a growing season or longer. Its Montana guidance for fall is to ease off from September so plants harden off, then water the root area thoroughly after leaf fall and before the ground freezes, which helps prevent winter kill. Our guide to watering trees through drought covers the years after that.

What protects a young trunk, and what kills new trees?

Thin young bark is vulnerable to winter sunscald, usually on the southwest side. Utah State Extension recommends a light-colored tree wrap put on in fall and removed in spring, since wrap left on through summer can harbor insects. In much of western Montana the trunk also needs a guard against browsing and antler rubbing, which our guide to deer and elk damage covers.

The DNRC nursery's list of what kills seedlings is short and applies just as well to yard trees: roots that dried out, planting at the wrong depth, air pockets or over-packed soil, and planting too late in spring. Add burlap and wire left on, mulch against the trunk, and a forgotten stake tie, and you have most of the common early failures.

Two last checks before you dig. In the City of Missoula, a tree planted in the boulevard or other public right-of-way needs a signed permit from the Urban Forestry Division, as our guide to Missoula tree permits explains. And look up for overhead lines. More planting and care topics are collected in the Montana Tree Guide.

HJ Property Care's tree services pick up once a tree is in the ground: structural pruning in the early years, and a tree health assessment if a young tree is not putting on growth and you want to know why.

Call HJ Property Care & Tree Service at (406) 215-7319 or request a tree assessment and an ISA Certified Arborist will look at the tree with you.

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