Tree Planting and Establishment Practice Questions

Correct answer: A. Level with or slightly above the surrounding grade

Planting depth is set by the trunk flare, where the topmost roots spread out from the trunk, and it should finish level with or just above the surrounding grade. Following the container's soil line is the tempting wrong answer, because nursery soil often already covers the flare, sometimes by an inch or more. Burying the flare, whether to keep roots moist or to steady the tree, invites stem-girdling roots and bark problems.

• B: The container soil line often already buries the flare; the flare, not the container, sets the depth.
• C: Even an inch or two of soil over the flare counts as planting too deep.
• D: Deep planting does not make a tree more stable; it leads to girdling roots and decline.

Sources: What is the proper planting depth for a tree?, Iowa State University Extension and Outreach (Yard and Garden) ; Tree Installation: Process and Practices (FNR-433-W), Purdue Extension

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Correct answer: D. Roughly 80 to 95 percent

Colorado State University Extension notes that only 5-20% of the small roots stay in the root ball of a field-dug tree, so 80-95% are left in the field; Purdue Extension likewise says 80% or more can be left behind. That loss is why newly planted B&B trees are under water stress until new roots grow. The lower figures reflect the common but mistaken belief that the ball holds most of the roots.

• A: This is close to the share of small roots that stays in the ball, not the share left behind.
• B: Far more than a third of the small roots are cut off at digging.
• C: The loss of small, absorbing roots is much greater than half.

Sources: Science of Planting Trees (CMG GardenNotes #630-#636), Colorado State University Extension ; Tree Installation: Process and Practices (FNR-433-W), Purdue Extension

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Correct answer: A. Shave off the outer 1 to 1.5 inches of the root ball

Colorado State University Extension notes that research has found the old standard of making slits on four sides of the root ball is not an adequate fix for circling roots, and that current standards instead call for using a knife, saw or pruners to shave off the outer 1 to 1.5 inches of the ball. Purdue Extension gives similar advice to box or shave the root system before planting. Leaving the ball intact or simply soaking it leaves circling roots in place to become stem-girdling roots later.

• B: Slitting the sides was the older practice and does not adequately remove circling roots.
• C: Circling roots left in place can later girdle the trunk.
• D: Soaking does not straighten or remove circling roots.

Sources: Science of Planting Trees (CMG GardenNotes #630-#636), Colorado State University Extension ; Tree Installation: Process and Practices (FNR-433-W), Purdue Extension

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Correct answer: A. Add soil to the bottom and firm it so the ball sits at the right height

A root ball set on loose soil sinks as that soil settles, leaving the tree too deep. UF/IFAS advises adding soil to the bottom of an over-dug hole and compacting it with your foot, and University of Maryland Extension cautions against loosening the soil at the hole's base, to keep the tree from settling. Leaving loose soil to encourage deep rooting is the tempting wrong answer; the loose layer simply compresses and the tree settles.

• B: Loose soil under the ball compresses, so the tree sinks; University of Maryland Extension says not to loosen the bottom of the hole for this reason.
• C: Setting the ball too low and adding soil on top buries the root flare.
• D: UF/IFAS fixes an over-dug hole by adding soil to the bottom and firming it, not by filling it with mulch.

Sources: Chapter 11 — Planting and Establishing Trees (ENH1061/EP314), archival copy, UF/IFAS Extension (EDIS) ; Trees Planted Too Deeply, University of Maryland Extension

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Correct answer: C. After the tree is set and steadied in the hole, so the ball holds together

The wrapping holds the root ball together while the tree is moved, so Colorado State University Extension says the burlap, wire basket and twine are not to come off until the tree has been set in place, and Clemson Extension likewise says to take off the upper part of the wire basket once the ball is positioned in the hole. Stripping the materials before the tree is in the hole risks a cracked or crumbling ball. Waiting a year is too late; the guidance is to take the materials off at planting, once the ball is in place.

• A: Stripping the wrapping before shipping lets the root ball crack apart.
• B: The wrapping should stay on until the tree is positioned, to keep the ball from breaking.
• D: Once the hole is backfilled the upper wrapping can no longer be removed, and twine left at the trunk can girdle it.

Sources: Science of Planting Trees (CMG GardenNotes #630-#636), Colorado State University Extension ; Planting Trees Correctly (HGIC 1001), Clemson Cooperative Extension, Home & Garden Information Center

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Correct answer: D. Roots keep growing in the still-warm soil while cool air cuts water loss

In early fall the air cools faster than the soil. UNH Extension explains that cool weather reduces water loss through the leaves, and once the air is cooler than the soil, shoot growth stops while roots keep developing until the soil drops below about 40°F. Purdue Extension likewise calls early fall the best time to plant most trees in Indiana because roots can establish before the ground freezes. The benefit comes from root growth before the freeze, so new trees still need watering in fall.

• A: Frozen soil stops root growth; the benefit comes from root growth before the freeze.
• B: Shoot growth stops in fall; the advantage is root growth, not crown growth.
• C: Roots in warm fall soil are active, and new trees still need watering until the ground freezes.

Sources: Is fall a good time to plant trees and shrubs?, University of New Hampshire Cooperative Extension ; Tree Installation: Process and Practices (FNR-433-W), Purdue Extension

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Correct answer: B. Directly over the root ball, where the roots still are

Right after planting, the tree's roots are still inside the root ball and have not grown into the surrounding soil. Clemson Extension says the root ball must be watered directly at first, and UF/IFAS advises applying establishment irrigation to the top of the root ball. Watering only at the drip line sounds like a way to draw roots outward, but it misses the roots the tree actually has, so the ball can dry out even when the soil around it is moist.

• A: Roots have not reached the drip line yet, so water there misses them.
• C: Keeping the ball dry starves the only roots the tree has.
• D: Spreading water across a lawn rarely keeps a new root ball moist.

Sources: Planting Trees Correctly (HGIC 1001), Clemson Cooperative Extension, Home & Garden Information Center ; Chapter 11 — Planting and Establishing Trees (ENH1061/EP314), archival copy, UF/IFAS Extension (EDIS)

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Correct answer: A. Moist mulch against the bark can rot it, and roots may grow up into it

A mulch volcano keeps the bark at the base of the trunk constantly moist. UF/IFAS warns that piling mulch against the trunk can rot it and cut off oxygen to roots, and that roots grow up into the moist, well-aerated pile, where stem-girdling roots can form. The belief that deep mulch speeds establishment by keeping roots cool and moist is the tempting mistake; mulch belongs in a wide, moderate layer that does not touch the trunk, whatever chips are used.

• B: Mulch piled deep against the trunk harms rather than speeds establishment.
• C: Any mulch type causes these problems when piled against the trunk.
• D: A pH change is not the main concern; bark rot and root problems are.

Sources: Chapter 11 — Planting and Establishing Trees (ENH1061/EP314), archival copy, UF/IFAS Extension (EDIS) ; Chapter 11 — Planting and Establishing Trees (ENH1061/EP314), archival copy, UF/IFAS Extension (EDIS)

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Correct answer: B. A container-grown tree with a light root ball on an open, windy site

Staking is meant to keep the root ball from shifting until new roots anchor it. Purdue Extension names container-grown trees whose root balls are small and light, along with open sites exposed to strong winds, as situations that call for support. Staking every tree is the tempting wrong answer, but most trees establish well without it, wind movement helps the trunk and roots develop, and restricting movement reduces rather than increases trunk diameter growth.

• A: A heavy root ball on a sheltered site normally holds the tree without stakes.
• C: Most trees do not need staking, and wind movement helps the trunk and roots develop.
• D: A self-supporting trunk does not need staking, and restricting movement reduces trunk diameter growth.

Sources: Tree Support Systems (FNR-547-W), Purdue Extension ; Tree Support Systems (FNR-547-W), Purdue Extension

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Correct answer: D. Remove only dead or broken branches, plus a competing leader if needed

A new tree needs as many leaves as it can keep, because leaves make its food and help it recover from transplant shock. The USDA Forest Service Tree Owner's Manual says to prune only broken or dead branches at planting, plus competing leaders if present. Cutting back the crown to balance lost roots is the classic wrong answer: Clemson Extension notes that pruning to make up for root loss does not ease transplant shock unless the tree is short of water. Heading cuts and stripping lower limbs also remove needed leaf area.

• A: Pruning to balance root loss is an outdated practice that research does not support.
• B: Heading back tips removes leaf area and produces weak, crowded sprouts.
• C: Removing the lower limbs at planting takes away leaf area the tree needs to establish.

Sources: Tree Owner's Manual for the Northeastern and Midwestern United States (NA-FR-04-07), USDA Forest Service, Northeastern Area State and Private Forestry ; Planting Trees Correctly (HGIC 1001), Clemson Cooperative Extension, Home & Garden Information Center

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