Here’s an article by Roy Berendsohn for Popular Mechanics.
Spring, or fall? It turns our there’s more than one right time for planting, but there’s only one right way to do it.
People always ask me, “When’s the best time to plant a tree?” For as long as I can remember, I’ve answered without needing a second to think: in the fall. That gives the tree a chance to acclimate to its surroundings, I tell them, before the stress of summer comes on. I’ve known this since boyhood.
“Then why do garden centers always have an acre of great-looking trees out in the spring?” a colleague asked me recently. I thought for a second. It was true.
“Because they want to sell you stuff,” I said.
At his insistence—and to prove myself right—I dialed three tree experts for corroboration. It took only one call to prove me wrong. Carrie Hennessy, a horticulturist at Johnson’s Nursery, in Menomonee Falls, Wisconsin, at first had me thinking she was on my side. “Fall is a great time to plant.”
Then: “But at those big retailers, you usually get the best quality material in the spring.”
Maybe it was a Midwestern thing. So I called two more experts, Joey Barton, a second-generation plantsman at Barton Nurseries in Edison, New Jersey, and Sarah Elvington at the Plant Oregon nursery in Talent, Oregon. To rub potting soil in the wound, they told me the spring months gave trees plenty of time to prepare for summer.
I now stand before you a changed man, offering you advice on how to plant a tree in your yard this spring, which apparently is not such a bad idea. (Note: This advice also works in the fall, which is still a better idea.)
1. Assess Your Yard
Start by sending a soil sample to the nearest Land-Grant University extension office—every state has one. For about $20 to $40, they will tell you the nitrogen, phosphorus, potassium, pH, and organic material levels so you’ll know if your ground needs soil amendments when you plant.
While you’re waiting for the results, check the soil depth in your potential planting area, says Jim Barborinas, an International Society of Arboriculture certified arborist who runs Urban Forestry Services in Mount Vernon, Washington. “Dig at least two feet down, or use a soil probe, looking for clay and backfill.” Yards in urban spaces, he warns, are often filled with gravel that will need to be replaced. You can also alleviate clay soil, says Hennessy, by backfilling around the root ball with a mix of one part compost to two parts existing soil.
2. Research and Shop
Your ideal tree species depends on soil, climate, sun exposure, and space. To narrow your choices, visit the Arbor Day Foundation’s Tree Wizard tool for a list of matches. When considering size and growth, your tree should still fit comfortably in the available space 25 years from now, says Barborinas. “And when you’re browsing trees, look for a good single leader, well-spaced lateral limbs, fat healthy buds, and no physical damage.”
3. Prep and Plant
Measure the diameter of the root ball, then rototill a circle that measures five times the diameter across (see opposite). That will give your roots more space to grow. With a round-point shovel, dig a dish-shaped hole that’s twice the diameter of the root ball and deep enough that only the tree’s root flare will be aboveground. If the root ball is covered with burlap, that can be left in the hole after it’s unwrapped.
Step 1: Rototill a circular area five times the diameter of the root ball.
Step 2: Dig a saucer-shaped hole in this rototilled area slightly less or equal to the root ball’s height and twice its diameter.
Step 3: Place the sapling gently in the planting hole after removing any plastic or wire from the root ball.
Step 4: Check that the tree is plumb, and gently backfill, compact the soil, and water the tree.
Step 5: Spread two to three inches of mulch over the planting hole. Leave the root flare, where roots meet the stem, exposed.
Step 6: The soil should feel moist but not muddy. Add water as needed.
When digging in front or side yards or near the street, dial 811 at least three days before planting. This allows utility marking crews sufficient time to visit the site and mark utility locations.
How to Water a Tree
One of the most common mistakes we see is that people overwater, says Barton. “It’s not unusual to dig out a dead plant and find a puddle of water in the bottom of the planting hole.”
To avoid drowning a new tree, Barborinas prescribes watering it based on its size. Set your garden hose to a trickle and place it over the root ball. Let it run ten minutes for every inch of the trunk’s diameter. (Two inches across means 20 minutes.) Or for conifers, he says, give the tree two minutes for every foot of height.
Begin watering weekly, and then adjust for the soil. Clay soil traps water, requiring less work on your part, while loose and sandy soils drain fast. A simple test to tell if your tree is getting enough water, says Barton, is to stick your finger in the planting hole and wiggle it around. It should be moist, not wet or dry.