To celebrate Earth Day next week, we'd like to share Carla Emery's instructions for planting a tree. Emery loves trees, and is an enthusiastic advocate for guerrilla tree planting.
In general, the best time to plant a tree is in the early spring or the late fall, but research your specific plant in case of exceptions. Where to plant is the spot where the tree will have the amount of sunshine it needs - full or partial, as specified; full if not specified. And, if it isn't hardy, plant it where it will have shelter from the wind. Plant big deciduous (shade) trees on the south side of the house where they will shade in summer and let warming light enter your windows in the winter. Conifers do well as winter windbreaks on the north or windy side of the house. (Wisely placed trees can improve your home's heating/cooling situation a lot!)
Digging a Hole: Dig planting holes wide and shallow, no deeper than the rootball's size, and make them wider than needed to accommodate the tree's spreading roots. The larger the area that you dig up around the hole in preparation for planting the tree, the easier it will be for its roots to spread and find food and water. Remove any grass for 3 feet in diameter.
Planting the Rootball
- Unpot the Tree. Speed matters. Don't let the roots or rootball dry out. Care matters also. Don't let the roots or rootball break. Your plant either will be "bare-rooted" and wrapped in some sort of protective substance or will come with the roots in a ball of dirt in some kind of container to hold it together - a peat pot, burlap, wire basket, or bag. If it's a metal pot, cut off the pot with tin snips. Tear it off if it's made of paper. You have to get as much of the wrapping off as possible without actually harming the rootball. This may have you struggling with knives, wire cutters, etc. Untreated burlap can, if necessary, be planted with the tree.
- Double-Check Hole Depth. Do this by setting the tree in the hole to see how it fits. The "collar" (or "crown" or "root flare") should be just at soil level or a little above (to allow for mulch). Usually it's easy to see because you'll be looking for the same soil line that the tree had at the nursery. Trees planted too deep can die within a few years, or develop problems as many as 15 years later.
- Set Tree in Hole. Then spread out the roots. If you see any girdling, damaged, or circling roots, cut them off. Try to lay the roots out in a way that they make good, straight contact with their new soil.
- Fill in Dirt. Place dirt over and around it. Don't add anything to the dirt you're going to put back into the hole to cover the tree roots - not peat moss, not fertilizer. It does more harm than good to spot fertilize a newly planted tree. This is because it tends to make the soil around the tree roots of a significantly different composition from the soil next to it. Water doesn't move normally across the difference. The result is a tree that's liable to be abnormally wet, or too dry. Don't bury incompletely decomposed organic litter around the seedling tree either. This can mess up the pH, the nutrient balances, and the populations of microscopic soil creatures. On the other hand, fully composted organic material that is evenly distributed across the top of the ground in your young tree's area could be helpful. Stomp dirt all around it to be firm and create a depression into which water can settle.
- The First Soaking. When soil is dry, watering the tree as soon as possible after planting is critical for its survival. Use water also for the final settling of the soil. If additional settling occurs, add more soil, but don't step on the wet soil around the tree.
- Mulch. Mulching the surface of the soil around your newly planted trees 2-4 inches deep does help them by controlling competition and gradually releasing nutrients. In nature, trees mulch themselves every fall. By keeping weeds away, retaining water, and moderating the soil temperature, mulch improves the chances of survival for your tree. But never let mulch pile up against the trunk. After mulching the planting pit, brush back the mulch that is in contact with the trunk.
- Avoid Staking. Natural flexing is necessary for the plant to develop a normally strong trunk and roots. Use staking only if needed to hold the tree up until the roots have become established (usually within a year). To stake, use 1 or 2 wooden stakes (pipe or rebar are too hard to pull out), which have been pounded firmly into undisturbed soil. Place the tie about a third of the way up the tree in order to allow maximum trunk movement. Use soft, flat tie material (inner tube, flat soaker garden hose, commercial products). Never use straight twine or electric, or any other type of wire, against a trunk. Remove stakes and ties as soon as possible. Trees are frequently girdled by ties that people forgot to take off.
- Prune. But do not prune the tree top to "compensate for root loss." That's a myth. You may prune to take off broken, rubbing, and weak branches, but try not to remove more than 1⁄5 of the branches.
- Dirt Dam. Build a circular dirt dam to create a basin effect around the outer edge of your tree planting area to retain water. Trees need water that soaks in deeply to establish good root systems. Water trees a lot the first year or two and during a drought. Let the root zone dry out between waterings unless your tree is a swamp variety. Five to 15 gal. a week is typical.
- Care After Planting. Young trees benefit if they are irrigated, fertilized, and weeded, being a crop like any other. Water them at least twice a week. Regularly rescue them from weed and grass competitors. Or, easier and better yet, mulch around them so thoroughly the competition doesn't get through. If your trees don't grow well and aren't an obviously healthy green color, they need fertilizer. Spread some manure from your barnyard. However, there's such a thing as too much nitrogen, so spread it in reasonable amounts. For long-term care, young urban trees are most at risk for being bashed by cars or lawn mowers, or vandalized.