How to Plant Bare Root Trees in Clay Soil

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How to plant bare root trees in clay soil comes down to three decisions: how wide and how deep to dig, how high to set the trunk, and what, if anything, to add to the hole. Oklahoma State, Washington State and Kansas State extension publications all address those decisions. They agree on the digging, on keeping roots moist, and on leaving amendments out of the hole. They differ on how high to plant in clay.

This guide walks through their steps in order, shows where the three pages disagree, and says what they leave out, so you can apply the method to your own yard and tree.

Quick answer

• Dig the hole at least twice the spread of the roots, and no deeper than the original root depth, according to Oklahoma State.
• In clay, Oklahoma State advises planting one to two inches above grade and mulching right away.
• Washington State says the plant should be at grade or slightly above, and Kansas State says never to set the top of the root ball below grade.
• All three sources advise against adding amendments to the backfill, and all three ask you to keep the roots moist.

Choose a dormant tree and plan the spring window

Oklahoma State says that only deciduous plants can be transplanted with bare roots, and only when they are dormant or leafless. It also says spring is best for bare-root plants, with most of them planted “between mid-February and mid-April or up to the end of the frost period.” Kansas State gives a wider window: “The best time to plant is before trees break dormancy in spring or as leaves begin to change color in fall.”

Washington State adds two checks before you buy. Test the drainage first: “Test the area for drainage before you buy your plant.” Then make sure there is room for the mature size, because “Pruning to keep something small is not a good idea and is labor intensive over the life of the plant.” Because the three pages are written for different states, confirm your planting window with your local extension office.

Hold the roots moist until planting day

Oklahoma State says roots of bare-root plants “should be placed in water immediately upon receipt,” or lined out in a shallow trench until planting. Its warning is short: “Never leave roots exposed to air.” Kansas State covers a delay in planting: “If planting is delayed more than a few days, bare-root trees and shrubs should be covered with loose soil, straw, or mulch to protect roots.” The sources do not say how long roots can wait out of the ground.

Clay drains slowly, so depth and drainage come first

Kansas State says that establishing new plants in clay soils is a challenge. Oklahoma State adds that a poorly drained clay soil is “either too wet or too dry for all but the most durable trees and shrubs.”

Depth is the first decision in clay. Oklahoma State is direct about it: “Planting too deep is a major cause of plant failure, especially in poorly drained clay soil.” Washington State warns that standing water “can be the death knell for many plants,” and Oklahoma State says drainage problems “must be resolved before planting is done.” The site work comes first, before the tree goes in.

Inspect and trim the roots

Washington State says to wash away the soil, spread the circling roots outward, and cut off any broken or torn roots. Keep the washed soil out of the hole: “Do not put any of it back into the planting hole.” Oklahoma State agrees on trimming: “Broken and badly damaged roots should be removed.”

Dig wide, and respect the depth

Oklahoma State sets the hole’s limits: “no deeper than the original root depth and at least twice the spread of roots.” Washington State says “Dig a hole the depth of the root ball and twice the width,” and Kansas State recommends a hole “two to three times wider than the rootball.” For digging tools, see our garden fork guide.

Here is our arithmetic, using a made-up example rather than a source figure. Roots that spread 24 inches call for a hole at least 48 inches across under Oklahoma State’s rule (2 x 24), and 48 to 72 inches under Kansas State’s rule (2 x 24 and 3 x 24). Kansas State measures against the root ball, so treat its number as a rough check. Measure the spread on your own tree.

Kansas State writes its depth rule for balled and container trees: the hole should be as deep as the distance from the first set of lateral roots, the root flare, to the bottom of the root ball. For a bare-root tree, use the most conservative of the three limits when you set the spade.

How high to set the trunk in clay

This is where the three pages differ. Oklahoma State says: “Since most Oklahoma soils are clay, plant trees and shrubs one to two inches above grade.” For sandy soil it says to plant “at original grade in sandy soils.” It also notes that planting above grade leaves roots exposed to drying, so mulch goes on right away.

Washington State says the plant “should be at grade or slightly above.” Kansas State gives only the floor: “Never plant a tree so the top of the rootball is below the surrounding soil grade.” All three share that floor and differ only on how far above it to go. The sources do not explain how to choose a height for a given site, and they do not show how to find the root flare on a bare-root plant before planting.

Keep amendments out of the hole

The three sources agree here. Washington State says: “For permanent landscape plants, do not add soil amendments of any kind, regardless of your soil type.” Kansas State says: “Amending the backfill with peat moss, compost, or other material is not recommended.” Oklahoma State says it is “not beneficial to apply amendments to the backfill.”

Kansas State explains the effect: “the newly planted tree will grow an intensive root system throughout the planting hole with few roots penetrating the relatively heavy soil outside the planting hole.” Oklahoma State also says not to line the bottom of the hole with crushed stone or gravel, and adds: “Neither of these methods improves drainage.”

Washington State offers a different route for a site that will not drain: “Raised beds are a possible solution.” The source gives no dimensions for that. For soil volume in a raised bed, see our raised bed soil guide.

Backfill, firm and water in

Washington State says to refill the hole with the same native soil and pat gently with your hands. Oklahoma State says to “Add soil, press, but do not stomp to firm the soil around the roots.” Washington State puts it in three words: “No stomping!”

Oklahoma State then says to “Fill the hole with water and let it drain,” and to “Fill the hole with soil to the planting line on trunk and water again.” It adds: “Do not pack the soil again.” If the soil settles later, the same guide says to “bring it back up to grade with additional soil.”

Mulch, water and stake the first season

Washington State says to “Add a thick layer of organic mulch to retain moisture and retard weeds,” and to “Do not let the mulch touch the bark.” Oklahoma State names pine bark or straw and advises a grass-free circle around young trees for two years.

Washington State says new trees need “regular watering their first year or two.” Kansas State gives a soaking every 7 to 12 days for heavy loam or clay soil, and warns that “Overwatering fills pore space, forcing oxygen out of the soil and causing plants to wilt.” Kansas State adds that its guidelines may vary, so treat the figures as a starting point. For a hose attachment for watering new plants, see our hose attachment guide.

Washington State says that “Most of the time there is no need to stake at planting time.” If a stake is used, it says to “Remove all staking materials within a few months but no later than one year.”

Mistakes to avoid

• Digging deeper than the roots, which Oklahoma State links to plant failure in poorly drained clay.
• Mixing compost, peat moss or sand into the hole, which all three sources advise against.
• Lining the bottom of the hole with gravel, which Oklahoma State says does not improve drainage.
• Leaving the roots exposed to air, which Oklahoma State says never to do.
• Piling mulch against the trunk, which Washington State says not to do.
• Leaving a stake in place past one year, the limit Washington State sets.

How we chose

We limited the review to university and state extension publications that cover planting bare-root or balled trees, with attention to clay or poorly drained soil. We opened three pages with curl on 2026-10-22 and read the extracted text. A rule went into this guide only when a page stated it in plain words, and each quoted sentence was checked against the page text before it was used. Commercial nursery pages and general gardening sites were left out, because they could not be checked against a primary source. Numbers come from the sources, except the worked example, which is labeled as our arithmetic.

What we could not verify

The three pages were written for three different states, and none of them gives a planting window that fits every reader. None gives a root spread for a common tree, so the arithmetic above uses an example.

What the sources do not say

The pages do not say how long bare roots can wait before planting. They do not say how to decide between one to two inches above grade and at grade or slightly above on a particular site. They do not say how to find the root flare on a bare-root tree, since Kansas State writes its flare rule for balled and container trees. The watering figure from Kansas State is written for heavy loam or clay, and the page does not say how it changes in a dry summer or in a wet spring. No page gives a size for the root spread of a common tree.

Frequently asked questions

Should compost go into the hole for a clay site?

No, according to all three pages. Kansas State advises against adding peat moss, compost or other material to the backfill. Washington State says not to add soil amendments of any kind for permanent landscape plants, and Oklahoma State says it is usually not beneficial to amend the backfill.

How deep should the hole be for a bare-root tree?

Oklahoma State gives a depth no deeper than the original root depth, and Washington State uses the depth of the root ball. Kansas State writes its depth rule for balled and container trees, measured from the root flare to the bottom of the ball. In clay, the depth limit matters most, because Oklahoma State calls too much depth a major cause of plant failure.

How high above the soil should the trunk sit in clay?

Oklahoma State gives one to two inches above grade for clay. Washington State says at grade or slightly above, and Kansas State says the top of the root ball should never be below the surrounding soil grade. Treat grade as the floor, and check with your local extension office for the height that suits your site.

When is the best time to plant bare-root trees?

Oklahoma State gives mid-February to mid-April, or up to the end of the frost period, for most bare-root plants, and it says spring is best for bare-root plants. Kansas State says the best time is before trees break dormancy in spring or as leaves begin to change color in fall. Because the pages are written for different states, use your extension office for the window in your area.

Can a bare-root tree go into clay soil that stays wet?

The pages do not give a method for a site that stays wet after planting. Oklahoma State says soil drainage must be resolved before planting, and Washington State names raised beds as a possible solution. Neither page gives dimensions for a fix, so check with your local extension office before you dig.

Sources

• https://extension.okstate.edu/fact-sheets/planting-trees-and-shrubs.html (opened 2026-10-22)
• https://wpcdn.web.wsu.edu/extension/uploads/sites/57/2022/03/Plant-Bare-Root-Trees.pdf (opened 2026-10-22)
• https://bookstore.ksre.ksu.edu/pubs/MF402.pdf (opened 2026-10-22)