Plant the Spirit of the Season

How to select and grow a living holiday tree

12-01-1992 // Nancy Lloyd

With all that holiday shoping, don't forget to buy a present for the environment. Ties and fruitcakes may not be quite the thing, but how about a living Christmas tree - one you bring indoors for the holidays and then plant in your garden?

The tree not only adds value to your landscape, but can help filter impurities from the air, keep soil from eroding and buffer your house from wind in the winter and direct sun in the summer.In some yards, placing shade trees along a house's western and southern sides will eventually cut air-conditioning needs by as much as half.

Urban homes and landscapes especially need trees. Air conditioners roar away during summer as cities simmer 5 to 9 degrees hotter than the surrounding countryside. Yet about 100 million potential urban tree sites lie empty. Put trees in them, argues American Forests (formerly The American Forestry Association), and the cooling effect could reduce the nation's energy bill by some $4 billion.

Trees also trap carbon dioxide, one of the principle villains of potential global warming. Each tree absorbs the burden of carbon dioxide by 13 to 26 pounds a year, depending on how quickly the tree is growing.

To achieve these benefits, of course, you need to do more than shake the tinsel off and poke the tree in the soil. If the ground freezes in your climate, you'll need to dig a hole for the tree before soil hardens. Also you'll need to pamper the tree while it's indoors and, most importand, reconcile yourself to having the tree inside no more than seven days to prevent damage. And of course, you'll need to pick the right tree, one that thrives in your climate but that won't crowd your yard when it reaches its mature height. Following are some tips on how to select and plant the right gift for your environment:

Selecting a Healthy Tree: No matter where you live, you can find a tree that will have the look and feel of a traditional Christmas tree. However, many popular species of cut Christmas trees make ungainly landscape plants and are not suited to much of the country. For better choices, Holly Shimizu, horticulturist at the U.S. Botanic Garden in Washington, D.C., suggests the following:

For the Northeast, Shimizu recommends fir trees for their beautiful texture and soft needles. Some firs reach 300 feet, so she suggests a Douglas fir compacta (Pseudotsuga menziesii 'Compacta'), which grows only 50 feet high. If your landscape needs something smaller with softer lines, she suggests a weeping hemlock (Tsuga canadensis `Sargentii'), which grows 10 to 20 feet high. Weeping hemlocks thrive in moist soil across much of the northern and middle sections of the United States, even as far south as Georgia and Texas under the right conditions. Ask a local nursery for advice about your particular climate conditions.

Many regions of the country will suit the various spruces. A Serbian spruce(Picea omorika) "dances in the breeze," according to Shimizu. It thrives in moist places not prone to excessive winds, like the Northeast, Midwest or Pacific Northwest. Serbian spruces often grow about 40 feet in their first 40 years and can eventually reach 100 feet. The Brewer spruce (Picea brewerana), hardy in the middle third of the country, forms graceful drooping branches with white-banded needles, as if a winter frost had just crystallized. The compact blue spruce (Picea pungens `Compacta') grows more slowly, matures at 25 feet and does well in all but the hottest climates.

Even smaller, the dwarf Alberta spruce (Picea glauca var. albertiana) is a good choice for most climates. It grows into a dense, tidy pyramid less than 10 feet high. It will survive as a patio plant if you choose not to set it in the ground after Christmas. In northern areas, you will have to bring the potted spruce indoors each winter, but it can be used as a living Christmas tree year after year.

Pines, while "not the most elegant trees, do well in most parts of the country, including the South," says Shimizu. As Christmas trees, she recommends a dwarf conical variety, Pinus sylvestris `Compressa'.

For hot climates, Shimuzu suggests Arizona cypress (Cupressus arizonica). It does well in arid regions of Arizona, New Mexico and Texas, growing to 40 feet and filling out into a satisfying conical form.

Even if you live in South Florida or the Southwest, says Shimizu, you can still have the look of a traditional Christmas tree with a "pencil tree" (Euphorbia tirucalli), a succulent, spineless tree that grows about 30 feet high.

Since it takes three to five years to reshape a tree, choose one that already has a pleasing shape. Check trees for signs of insects or disease.

Most living Christmas trees are sold either in containers or balled and bur-lapped (B&B). Nurseries grow B&B trees in fields, then dig them and wrap the root ball in burlap. Look carefully at the root ball of a B&B tree. A tree with a cracked root ball was allowed to dry out at some point, so avoid it. Ropes should be firm, but avoid B&B trees being girdled by too-tight supports.

Check container trees carefully too. Soil should be moist. Avoid a tree with 'roots growing out of the pot from the top or through the hole in the bottom. This indicates neglect, because the tree should have been repotted in a larger container. If you think the tree is in a much larger pot than necessary, place your finger between the edge of the soil and the container. If you do not feel roots, you are paying for a small tree in a large pot.

Seven Days Indoors: Trees go dormant in the fall, but bringing a tree into a warm house in December may break dormancy and trigger new growth, which can doom the tree. The new growth will be too tender to withstand the cold when the tree goes outdoors again. To minimize the risk, leave the tree in the house no more than one week.

A Christmas tree next to a roaring fire looks great in pictures, but direct heat can damage live trees. Keep the room cool, and place the tree away from heat registers. Water daily to keep the root ball from drying out. (Don't mist if you decorated it with electric lights.)

Digging the Hole: Trees don't thrive in waterlogged soil, so test soil drainage before selecting a site. Dig a test hole 9 to 12 inches deep, and fill it with water. Twenty-four hours later, refill the hole with water. If standing water remains after 24 hours, you have poor drainage. Either find another location or raise the planting bed by adding 1 to 2 feet of a good top soil.

Dig the hole before frost. Otherwise frozen soil may prevent you from planting the tree. To encourage the tree's roots to grow horizontally, dig a wide hole, at least three times the width of the root ball but less than a foot deep. The hole should not be deeper than the root ball. Cover the soil with plastic to keep it from freezing or move the soil to a garage or shed.

Planting the Tree: For container plants, gently remove the tree, being careful not to pull the trunk or branches. In the past, experts warned gardeners not to disturb the root ball. New research, however, shows that if circling roots are left intact, they will continue to circle and choke the tree. To encourage horizontal root growth, make four shallow cuts on the root ball with a sharp knife, pruning shears or a shovel: Lay the tree on its side and make a half-inchdeep cut the length of the root ball. Rotating the tree 90 degrees at a time, repeat the cut on four sides, as if outlining quarters on an orange. Place the tree in the hole, and spread out the cut roots to encourage them to grow outward.

If you selected a B&B tree, loosen the burlap before placing the tree in the hole. Most "burlaps" are treated with preservatives to keep them from disintegrating or are made of synthetic materials. Neither will decompose, so remove and discard them before planting the tree.

If you're sure the burlap is an untreated natural fiber, however, it can be left to decompose around the root ball. Bury the burlap completely—any fabric above ground will act like a wick, drawing water away from the tree.

Locate the crown of the tree (where the roots and stem meet). Brush away any soil because the crown must be completely exposed for the tree to survive. Position the tree so the crown is 1 to 2 inches above the soil level, and, as you fill in the soil, remember to keep the crown free of soil or mulch.

Use only the original soil for backfill. Experts no longer recommend most of the traditional amendments such as a complete fertilizer, peat moss, compost or manure. If soil in the hole has significantly better nutrients or texture than surrounding soil, the tree's roots will not grow beyond the original hole. The exception is bone meal or other phosphorous, which can go into the backfill to encourage root growth. Distribute the addition evenly, since phosphorous stays where you put it.

Add backfill until the hole is two-thirds full. Tamp the soil gently, but leave small air pockets, which are necessary for a healthy tree.

Water around the root ball. If the root ball sinks, remove and replant the tree. After watering, fill the hole completely, and tamp the soil again.

Tree specialists no longer recommend a berm, or raised rim, to hold water around the root ball. While a berm keeps moisture near the tree in a drought, the berm can drown a tree after heavy rains.

Most trees less than 10 feet tall do not require staking. If stakes are necessary, use three stakes and remove them within three years. Conifers do not need tree wraps or antitranspirant sprays.

Cover the root area, at least 6 inches beyond the drip line, with 2 to 4 inches of mulch. Keep the mulch several inches away from the trunk of the tree, since mulch can harbor insects, fungus or disease, as well as provide a warm hiding place for rodents. All of these threats can damage the tree. Prune any damaged or misshapen branches. Water at a slow speed for an hour.

The First Two Years: Since plants have a harder time absorbing water through the ground in winter, they may need watering during the first two years. Place a tin can near the base of the tree, and measure the amount of snow or rain that falls each week. In any week with less than a half-inch of water, give the tree a slow, deep watering.

By adding a new tree each year, you will start a new Christmas tradition.

Virginian Nancy Lloyd writes and lectures about gardening. She has planted dozens of trees, which are all thriving.

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