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, how to water, and 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, and 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 more depth than the roots actually occupy, which for a young tree is usually the top foot. Dig a trench around the tree at that radius, undercut it, and slide a tarp beneath so the ball moves without breaking. Wrap it and keep it shaded.

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.

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, a newly planted tree needs roughly ten gallons a week per inch of trunk diameter, less whatever rain fell. 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 trunk size, weeks since planting and the week’s rain into gallons 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: 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, or a tree tube for a seedling. 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, and take the stakes out within a year, without exception.

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. Published field trials, and every planting we have watched, show the same result: the small tree catches the big one within a few years and passes it, 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.