Transplanting young trees: timing, water and protection

A transplanted tree loses most of its roots on the shovel. Everything about moving one well comes back to that fact: when to do it, how to dig and how to water. The same fact is why the small tree in a pot will be bigger in ten years than the eight-footer that cost ten times as much. This is how we move trees at the nursery and what we tell customers to do at home.

Move it while it is asleep

Transplant during dormancy, from leaf drop in fall until bud break in spring. A dormant tree has no leaves pulling water. Roots keep growing while the soil is above about 40 degrees, so a fall transplant has months of root growth before it has to support a crown. Early spring is the other window, and the better one for a few species that resent fall moves, among them oaks with a taproot, magnolias and dogwoods.

Never dig when the ground is frozen or waterlogged. Frozen soil shatters roots, and saturated soil smears into a glazed hole that roots cannot cross and compacts under your boots.

Dig the tree, not the hole, first

For a tree moved with soil on its roots, a working rule is about a foot of root ball width for each inch of trunk diameter, and no ball smaller than 16 inches across. For depth, the rule is no more than the roots actually occupy, which for a young tree is usually the top foot.

1. Water the tree the day before, so the soil holds together on the spade.
2. Dig a trench around the tree at that radius, a spade’s width wide and as deep as the roots go, then undercut the ball from the trench with the spade angled in toward the center.
3. Tip the ball gently to one side, slide a tarp beneath it, and tip it back so the tarp carries the weight.
4. Lift it by the tarp, never by the trunk, and keep it wrapped, shaded and damp until it goes in.

Bare-root trees, which is how most small trees are sold, are simpler to move but less forgiving: the fine roots dry out in minutes. Keep them wrapped in wet burlap or a bag from the moment they leave the soil until they go back in, never in sun or wind, and plant the same day. Soak them in a bucket for an hour or two before planting, not overnight.

Wide and shallow, flare high, nothing added

Dig the hole two or three times wider than the root spread and no deeper. Set the root flare, where the trunk widens into the first roots, at or an inch above the finished grade, on firm soil so it cannot sink. Spread bare roots out in their natural directions. Backfill with the soil that came out of the hole: no compost, no bagged soil, no fertilizer.

Then water slowly until the hole is full and let the water settle the soil; do not stomp it, which compacts the soil and breaks roots. Put a few inches of leaves over the whole area, pulled back from the trunk. Most of the ways a planting goes wrong happen in these ten minutes, so it is worth slowing down here.

The instruction to skip the compost is the one people argue with, so it is worth hearing from an extension service instead of from a nursery:

“Adding organic matter to the planting hole will slow root establishment and sometimes kill young trees and shrubs.” (University of Maryland Extension, Planting a Tree or Shrub)

Water for two summers

The first year decides whether a transplant lives, and the second decides whether it thrives. The rule is deep and infrequent: enough water each time to soak the whole root ball and the soil just beyond it, then let the top few inches dry before the next.

• First two weeks: every day, a slow soak at the base.
• Weeks three to twelve: every two to three days.
• After that: weekly through the first growing season, and through the second summer whenever a week goes by without an inch of rain.

As a starting point, University of Minnesota Extension gives a newly planted tree 1 to 1.5 gallons per inch of trunk diameter at each watering. It skips a watering only after more than an inch of rain in a day. Use a rain gauge and the finger test: push a finger into the soil beside the root ball, and if it is dry two knuckles down, water. If it is wet, wait, because more transplants drown in clay than dry out in sand.

Our watering calculator turns how the tree went in, its trunk size, the weeks since planting and the rain into gallons per watering and a schedule for the phase you are in. A tree is on its own after about a year and a half per inch of trunk diameter, except in drought.

Fence it from day one

Deer browse the tips, bucks shred the bark with their antlers in fall, and rabbits and voles gnaw the base under snow. Any of them can kill a young tree in one night, and it always happens the week before you get to the fence. Protect the tree the day it goes in.

Use a cylinder of welded wire four to five feet tall and wide enough that a deer cannot reach the leaves through it, staked so it cannot be pushed over. For a seedling, use a tree tube instead. Add a collar of hardware cloth at the base, pushed an inch or two into the soil, where rabbits and voles are around. Protecting trees from animals covers the details.

A tree that can stand on its own should not be staked; the sway builds a strong trunk and the roots that anchor it. If a tree cannot hold itself up, or the site is a wind tunnel, stake it loosely with a wide, soft strap low on the trunk. Take the stakes out within a year, without exception.

“Studies have shown that trees develop stronger trunks and roots if they are not staked; however, it may be required when planting bare root stock or on windy sites.” (International Society of Arboriculture, Planting a Tree)

Why small transplants win

A seedling loses most of its roots when it is dug, and so does a two-inch-caliper tree. The seedling grows them back in a season. The big tree spends years rebuilding, putting on almost no height while it does, and stays vulnerable to drought the whole time. Most published field trials, and every planting we have watched at Blue Whale Trees, show the same result: the small tree catches the big one within a few years and passes it. It does so with a better root system and a lower price.

Buy the size you can carry, plant it right, water it for two summers, and keep the deer off it. That is the whole recipe, and it is why everything we grow is sold small: saplings, acorns and seed.

Common questions

When is the best time to move a young tree?

Any time it is dormant, from leaf drop in fall until bud break in spring. A fall move gives the roots months of growth while the soil stays above about 40 degrees, and early spring is the safer choice for the species that resent a fall move.

How do I move a small tree without killing it?

Dig it while it is dormant, with a root ball a foot wide for each inch of trunk, and keep the roots damp until it is replanted. Water it deeply for two summers and cage it the day it goes in.

How much water does a newly moved tree need?

One to one and a half gallons per inch of trunk diameter at each watering, daily for the first two weeks and tapering to weekly by the end of the first season. Only more than an inch of rain in a day replaces a watering.

How do I know if a moved tree is in shock?

Wilting, scorched leaf edges, yellowing and early leaf drop are the usual signs of transplant shock, and they can last into a second year. Green under the bark of a scratched twig means the tree is alive, and the soil 6 inches down at the root ball says whether it needs water.

My new tree is leaning: will it straighten?

If the root ball sits firm, yes: over the years the trunk adds wood and its top grows back upright toward the light, leaving a gentle sweep at the base. If the root ball rocks, set the tree upright and stake it loosely for one growing season only, as the new-tree check advises for roots not yet anchored. A bare-root sapling that arrives with a bend is set straight in the hole, root flare at grade, and its new growth heads upright toward the light.