Why fall wins
The best time to plant trees is when the soil is still warm and the air has turned cool, which here usually means mid-September into November. The leaves are winding down, so the tree is losing less water through them. Meanwhile the roots keep growing into the surrounding soil for weeks after the canopy goes quiet, up until the ground gets cold.
By spring, a fall-planted tree has a head start on the roots it needs before the first summer heat. Fall rain and cooler days also mean less watering than a spring or summer planting.
Spring is a good second choice. Plant early, before the buds break if you can, so the roots get a few weeks before the leaves start pulling water. A spring tree goes into its first summer with a smaller root system and needs closer watching through July and August. Summer planting works for container-grown trees if someone is prepared to water on a schedule through every dry spell. Balled-and-burlapped trees dug in summer have a harder time.
Some trees do better planted in spring
A handful of species are slow to root in after transplanting, and nurseries and extension services often recommend planting them in spring. They are commonly listed as:
- Birch
- Magnolia
- Flowering dogwood
- The red oak group: red, pin and scarlet oak
- Black gum
- Sweetgum
- Tulip poplar
What they share is a root system that is fleshy, sparse or slow to regenerate. A fall-planted tree of this kind can go into winter without enough new root to keep it supplied.
Treat it as a risk to weigh. Plenty of these trees planted in fall do fine, especially container-grown stock that is watered properly. Where there is a choice, though, give them a spring start.
Planting a tree, start to finish
Call before you dig
Pennsylvania law requires a call to PA One Call (811) at least three business days before any digging, so buried utility lines can be marked.
Find the root flare
Scrape soil off the top of the root ball until the first main root shows. That is your depth mark, not the top of the ball.
Dig wide, not deep
Two to three times the width of the ball, and no deeper than the distance from the flare to the bottom of the ball.
Set it and straighten it
Lift by the ball, not the trunk. Check it from two directions before anything is cut away.
Remove what does not belong
Twine off, burlap cut back, wire basket cut away at least from the top half. On container stock, loosen or cut circling roots.
Backfill and water in
Use the native soil, settle it with water in stages, and leave the flare exposed at grade.
Mulch, and stake only if needed
Two to three inches of mulch in a wide ring, kept off the bark. Stakes only for trees that cannot stand on their own, and off after a year.
Water through two seasons
Deep, slow watering over the ball whenever rain falls short, until the ground freezes in the first fall and through the following summer.
Depth and the root flare
A tree buried too deep does not die that year. Its bark stays wet below ground, roots grow toward the air and can wrap around the trunk, and the decline shows up years later as a thin canopy and a trunk that goes straight into the ground like a telephone pole. If you can see a flare on your tree, it was planted right.
Every tree widens at the base where the trunk becomes roots. That is the root flare, and it belongs at or slightly above finished grade. Nursery trees often arrive with extra soil piled over the flare, so the top of the root ball is not a reliable guide.
Scrape soil away from the trunk until you find the first main root, and set the tree so that root sits at the surface. In heavy clay, setting it an inch or two high is a sensible margin.
Dig the hole no deeper than the root ball, so the ball rests on firm, undisturbed soil and does not sink after watering. Dig it wide, typically two to three times the ball’s diameter, with sloping sides. Roots spread outward through the top foot or so of soil, not down.
In clay, rough up the walls of the hole with a shovel. Smooth, glazed walls act like the sides of a pot, and water collects in the hole as if it were a bathtub.
Burlap, wire, twine and circling roots
On a balled-and-burlapped tree, set it in the hole and get it straight first. Then cut the twine from around the trunk, pull the burlap back from the top of the ball, and cut away as much as you can reach. Synthetic or treated burlap does not rot and has to come off entirely. Cut the wire basket away at least from the top half of the ball, more if the ball holds together. Wire and twine left on a trunk will girdle it as it thickens.
Container trees have the opposite problem. Roots that hit the side of a pot turn and circle, and they keep circling after planting.
Tease the outer roots loose, cut through any that wrap the ball, and on badly pot-bound stock shave the outer inch of the root ball off on all sides. That looks rough, but it is how the roots get out into the soil instead of strangling the tree from the inside.
Backfill with the soil that came out of the hole, broken up and free of large clods. Heavy amendment of a single hole creates a soft pocket the roots are reluctant to leave, and in clay it collects water. Settle the backfill with water in stages instead of stamping it down hard, which squeezes the air out of clay and leaves the roots little to grow into. Firm it just enough that the tree stands straight on its own.
Water, mulch and stakes for the first two years
A new tree’s whole root system is the ball it came in, and that ball dries out faster than the soil around it. Water slowly and deeply over the ball and just beyond it. Water often for the first few weeks, then about weekly whenever rain does not do it, through two full growing seasons. Keep watering a fall planting until the ground freezes.
Larger trees take longer to establish and need watching longer. Check by pushing a finger or a trowel into the ball, not by looking at the lawn.
Mulch typically two to three inches deep, in a wide ring, pulled back a few inches from the trunk. Mulch piled up against the bark in a cone, the mulch volcano, holds moisture against the trunk, invites rot and rodents, and encourages roots to grow up into the mulch and around the trunk. It is one of the most common ways new trees are harmed.
Most trees do not need staking. Stake only a tree that will not stand on its own: a top-heavy evergreen, a loose root ball, an exposed windy spot. Use wide, flexible ties set low on the trunk with some slack, and remove everything after one growing season. A trunk that sways a little in the wind grows thicker and stronger. One held rigid for years grows weak, and forgotten ties cut into the bark.
Privacy screens: arborvitae and the alternatives
A single row of arborvitae is the default screen, and it has two weaknesses. Spacing is decided by the mature width of the variety, not the size on the truck. Planting a little closer than the mature width gives a faster screen. Planting much closer gives trees that compete for light and lose their lower branches.
The second weakness is deer. Eastern arborvitae is a favorite winter food, and where deer are heavy it ends up bare as high as a deer can reach.
A mixed screen holds up better. Combine arborvitae with evergreens that deer generally browse less, such as eastern red cedar, spruce and American holly, and stagger them in a double row if the bed is deep enough. If one species gets hit by deer, insects or disease, the screen thins in places instead of failing all along the property line.
| Species | Deer | Notes |
|---|---|---|
| Eastern arborvitae | A favorite winter food | The default screen; bare as high as a deer can reach where deer are heavy |
| Eastern red cedar | Generally browsed less | Mix with arborvitae |
| Spruce | Generally browsed less | Mix with arborvitae |
| American holly | Generally browsed less | Mix with arborvitae |