Why go to the trouble of planting a tree in autumn? The reason is that it makes for a stronger, better-established tree. The soil is warm, but the air is cooling down, so there’s less stress on the tree. There’s usually more rainfall, and in most places there’s still months before frost. The tree is done making leaves, so it can expend its energy developing a deep root system. This makes for a resilient tree whose top growth will take off next spring.
By “fall” tree experts mean anytime from mid-August to mid-October, depending on where you live. You should plant at least six weeks before the first frost to give the tree time to settle in, so the earlier frost arrives in your area, the earlier you should plant. The Davey Tree Company says that as long as there are leaves on the trees in your area, and the soil is 50 degrees F or warmer according to a soil thermometer, you should be safe.
Photograph of maple tree by ParentingPatch, CC BY-SA 3.0, via Wikimedia Commons.
Some tips when choosing a fall-planted tree:
Choose a young, small tree. Smaller trees take to the surrounding soil quicker than larger, more mature trees, which can take years for their roots to establish.
Check the root system before buying to be sure the tree isn’t rootbound. Rootbound is when there’s more roots than soil in the container, and the roots are circling the pot. You might be able to tease some out, but the roots of a severely potbound tree might keep growing in circles even in the ground.
While you can often find plants on sale in big box stores and garden centers at this time, make sure a tree hasn’t been ignored or mistreated. It should look healthy, with no dead branches, split or peeling bark, or evidence of disease or insect damage.
According to the Morton Arboretum in Lisle, IL, conifers need more time to establish than hardwood trees, and so should be planted in late summer or very early fall, while the soil is 60 degrees F or warmer. Other experts advise planting conifers and broad-leaved evergreens such as rhododendrons only in the spring.
Some trees the Morton Arboretum says can be planted in fall include catalpa, crabapple, hawthorn, honey locust, elm, Kentucky coffee tree, linden, maple, and sycamore.
They recommend planting these trees only in spring: American hornbeam, ginkgo, larch, magnolia, hemlock, sweetgum, tuliptree, and willow.
Photograph of catalpa by Jebulon, CC0, via Wikimedia Commons.
How to plant:
Dig a hole that’s at least twice as wide as the tree’s container, or twice the size of the rootball if balled-and-burlapped. The wider the area of loose soil around the hole, the easier it will be for the roots to spread. Don’t dig any deeper than the height of the rootball, and don’t amend the soil in the hole.
Tease out any circling roots. If the tree is really potbound, you may need to slice into the rootball from top to bottom with a knife to free the roots so they can spread into the soil.
Set the tree in the hole so that the soil line of the rootball is just slightly above the level of the surrounding soil. The tree should be set high enough so that it does not sink into the hole once the soil settles.
Once planted, water the tree in well, and mulch around it with wood chips, bark, or shredded leaves two to four inches deep. This will help hold moisture in the soil and protect from frost heaving. Do not pile mulch against the trunk; keep it three or four inches away in order to keep moisture from rotting the bark.
You might need to put a tree tube or netting around the tree to keep animals from nibbling on the tender bark.
The most important piece of advice? Keep it watered. Any newly planted tree, whether spring or fall planted, that isn’t watered deeply and consistently will struggle and likely die. Depending on rainfall amounts, at first you may need to water two or three times a week after planting and into winter, and then at least weekly during the next growing season, meaning from early spring right through late fall. Lack of water is the biggest reason new trees fail.
Plant a tree now and you will have the pleasure of watching it take off and flourish in the spring.
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