By Robert Cox, Colorado State University Cooperative Extension agent, horticulture
Arbor Day just might be our most convenient holiday. You can celebrate it any day you plant a tree.
So if you missed it yesterday, opportunity still awaits. While you're waiting for the ground to dry out or for the little deciduous trees at the nursery to leaf out -- so you can pick just the right one -- here are some tree-planting pointers.
Here's also some advice: Some trees are better to plant in the home landscape than others. Most of us have small yards and nearby neighbors. We don't want a tree that grows so fast it's subject to limb breakage or one with roots that will crack your neighbor's cement driveway or clog your sewer lines. Fast-growing trees, such as cottonwoods, poplars, silver maples and willows will do just that.
These trees, along with aspen, also are susceptible to several insects and diseases. With such a variety available to choose from, why not by-pass these species and choose others that will be more rewarding in the long run?
Some folks lack the patience for slower growing trees, thinking they'll "never see their benefits." Consider, however, that benefits begin from Day 1. Even a small tree makes a visual impact right away and contributes environmental benefits.
The Denver area's dry climate and generally poor, alkaline soils create difficult conditions for trees. By following these guidelines, you'll compensate for some of Mother Nature's shortcomings.
Site suitability will determine which trees to plant. Trees need room to develop root systems underground and branches above ground. Don't plant a tree that will grow too large in a small area. Also avoid planting trees that will grow large under power or telephone lines or too close to buildings.
Consider planting for energy conservation. Deciduous trees will shade the west, south and east sides of the home in summer, and evergreen trees planted along the west and north edges of the lot will provide winter windbreaks.
Once you've determined the site, consider your reasons for planting a tree. Do you want privacy, increased property values, a windbreak, shade, a sound barrier, fall color, flowers, fruit or a bird habitat?
Digging the hole
If you live in a suburban development, digging the hole may be not be as easy as you think. Underground lines -- telephone, electric or cable television -- may lie in the same spot as you'd like your tree. You could be liable for damage done to lines. Contact your local utility for line location if there's any chance of damaging lines.
To prepare the site, mark an area at least three times the diameter of the tree's rootball. Excavate the area with a pick and spade. In clay soil, dig to a depth 2 - 4 inches shallower than the height of the rootball. In sandy soil, dig to a depth equal to the rootball. The bottom of the hole should be firm and undisturbed.
To the excavated soil, add 25 percent by volume, of a coarse organic amendment, such as sphagnum peat, compost or aged manure. Mix it well with the excavated soil; this is your backfill.
Planting the tree
If possible, plant when the weather is cool, cloudy and humid, but not windy. If you can't plant right away, keep the tree in a cool, shady, protected spot and keep the roots moist. It helps to soak bare root trees and shrubs in a bucket of water overnight before planting.
Remove plastic or metal containers from the rootball. Place the tree upright in the center of the planting hole. If the tree is in a fiber pot, tear away the sides. If the roots of a containerized tree are potbound, gently pull some of the roots loose and make a shallow slit in the rootball's sides with your finger or a knife.
For balled and burlapped trees, once the tree is in the hole and partially backfilled, cut any rope tied around the trunk and pull the burlap away from the trunk. Cut any reinforcement wire, removing as much as possible but be sure the rootball stays intact.
Continue shovel the backfill into the hole until roots are covered and most of the backfill is used. Don't tamp the soil with your feet.
Don't put fertilizer into the planting hole; it may cause root injury. Next spring, fertilize young trees lightly. Don't put too much faith in root stimulator solutions. They aren't necessary for transplant success.
Water the soil at low pressure using a hose or a "bubbler." Let the water, not your foot, settle the soil. If the soil settles below grade, add more backfill. Watering frequency, after the initial watering, depends on the soil, not the calendar. Dig with a trowel on the edge of the planting area. Soil that feels moist and holds together when squeezed doesn't need water. Overwatering drives air from the soil, causing root suffocation. Frequent, light watering promotes shallow root development. Mulching reduces the need to water frequently.
To stake or not to stake
Don't stake small trees or those not in the wind's path. Large evergreen trees, planted in a windy site, will need staking. To stake, run wire through grommeted staking straps or use wide strips of carpeting. (Do not use garden hose and wire.) A year of staking usually is enough. The tree needs some sway in the wind.
A forest tree provides its own mulch with several inches of leaves on the ground. We can imitate this by mulching the planting area with three to four inches of wood chips, chunk bark, straw, pine needles or shredded leaves. Don't use plastic beneath the mulch; water or air can't penetrate it. Fabric-type weed barriers are preferred.
Next winter, use crepe paper or other wraps on your deciduous tree trunks. Wrap the trunks about Nov. 1; remove around April 1. Do this for the first two or three seasons. This protects young trees from winter sunscald, a damaging condition that occurs when the southerly sun hits the trunk with too much intensity in winter months.
Photograph courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010