Growing Conifers

One of the real bonuses of growing conifers is that they are so easy to maintain. The following guidelines will help even novice gardeners grow conifers successfully.

When to Plant

Across most of the country, spring (early or late, depending on how far north you are) and early fall, when temperatures are cooler and rainfall more abundant, are the best times to plant conifers. To reduce transpiration or water loss from the tree, plant on an overcast day when there is ample soil moisture.

How to Plant

The hole you dig for your new conifer should be shallow and wide—twice the width of and more shallow than the height of the root ball. Unless the soil is very compacted or so light and porous that it retains very little moisture, you will not need to add organic matter. If soil drainage is a continual problem, consider creating a raised planting bed that has been amended to improve the soil.

When planting a conifer sold in a container, first loosen the roots by firmly tapping around the pot with the palm of your hand. Then, trim any roots that may be growing out of the drainage holes. If the plants are small, place your hand on the top of the pot, spreading your fingers so that the stem and the top of the soil are supported, and carefully slide the plant out, keeping the root ball intact. Tip large containers onto their sides to facilitate this process.

Many container-grown plants will have a mass of circling roots that should carefully be loosened by hand or with a small hand cultivator prior to planting. This will prevent the roots from girdling and eventually killing the plant.

to prevent the root ball from breaking apart. B&B conifers are sometimes wrapped in plastic "burlap" or treated burlap, which may be green in color. These coverings do not decompose and should be removed before you fill in the hole with soil.

Plants in untreated burlap should be set into the prepared hole, which should then be filled about a third of the way with soil. Next, cut the burlap and cord away from the trunk and roll the burlap back to expose the top of the soil. Finally, you can fill in the rest of the hole, burying the burlap.

No matter how the plant was grown, be sure that the trunk flare (where the trunk and roots meet) is slightly higher than the surrounding soil level to compensate for settling, especially if your soil is heavy or poorly drained. Some root balls have soil above the trunk flare and it is best to remove it. Use excess soil to create a saucer or rim around the plant. This will allow water to collect, keeping the plant moist until it is established, and will provide extra soil when settling occurs. Always water thoroughly after planting.

Diligent care is critical from the time of planting until new roots are established. For the first few weeks, check the plant every two to three days for signs of stress and water whenever the soil feels dry. Once the roots have grown out into the surrounding soil, which generally takes about three to six months, the plant can be checked less frequently.

Watering

Established plantings need supplemental water only during periods of prolonged drought. The amount of water will depend on the species and your soil type. On average, water thoroughly if the top two to three inches of soil feel dry. Deep waterings when needed are better than frequent, shallow waterings. It's important to note that conifers do not show signs of stress as readily as other plants. For example, they seldom wilt; instead, the overall plant color will lighten or fade and interior needles will turn brown.

To Stake or not to Stake

Conifers generally don't require staking, but there are three exceptions: Those used in very windy locations may need to be staked, but for no more than a year, long enough for anchor roots to develop sufficiently to support the plants. Staking is also beneficial for weeping or pendulous plants that are not yet self-supporting. Finally, if you want to espalier plants, they should be supported.

Mulching

Mulching conifers is essential. It maintains the relatively cool soil temperatures that most conifers prefer. Mulching also helps conserve water and reduces weed competition. However, the mulch should be no more than two to three inches deep, and should never come in contact with the trunks of your plants.

Fertilizing

Conifers are not heavy feeders and need only an annual application of a general, complete garden fertilizer such as 10-10-10 or 16-8-8, or a top dressing of well-rotted manure. It is best to fertilize in the early spring before the plants break dormancy, or in late fall before the soil freezes.

Pruning

As with any plant, dead or diseased conifer branches should be removed immediately, regardless of the time of year. Any other pruning should be done when the plant is dormant. Unlike many deciduous shrubs, most conifers can't re-sprout from older wood (yew, arborvitae and podocarpus are exceptions), and so a good rule of thumb is never to remove more than one-third of the total growth at a time. If you prune too drastically, the plant may never fully recover. Many of the dwarf varieties never need to be pruned, but do appreciate some thinning to allow air and sunlight to penetrate to the interior of the plant.

The most common method of pruning evergreens is known as "cutting" or "heading" back. Only part of the branch is pruned; the terminal or tip growth is trimmed to side or lateral buds or branches. This promotes thicker, more compact foliage and a smaller overall plant.

Pines are pruned in a special way, called candling, to control growth. Candles are the elongated shoots from which the current season's needles will emerge. To prune a pine, remove one-half to two-thirds of the candle growth in the spring. Gently break the tips off by hand when the needles are just pushing out of the shoot. Do not use pruners as the blades will also cut the tips of the remaining needles, causing them to brown and discolor.

A type of mutation called a reversion is common in dwarf or variegated selections. A reversion is when these cultivars change back to the plant's "species form." Cultivars of some species, such as sawara false cypress, are especially prone to reversion. Familiarity with your particular cultivar will enable you to spot—and remove—a renegade branch quickly. To be sure that you have removed the area where the mutation originated, make the cut in the stable growth just below the point where the reversion has occurred.

Transplanting

Sometimes a conifer will outgrow its location or you may decide that it really would look better on the other side of the yard. The most important factor when moving a conifer is the plant's size, which in turn determines the circumference of the root ball. Measure the trunk diameter about eight inches from the soil level. For each inch of diameter you should dig at least a foot in width of root ball. Consider hiring a professional to move any plant with a trunk diameter of much more than two inches.

Before digging, make sure that the soil is moist and the plant is in good health. Unhealthy specimens usually will not survive a transplant. Tie back branches so they are clear of the digging area. Then, mark the outline of the root ball in the soil as a guide. Begin by digging a trench around the outside of this guide line, clearing the soil from the hole. If you encounter large roots, cut them with pruning shears or loppers instead of the spade so that the roots do not tear and loosen the soil. Never walk or stand on top of the root ball while you are digging.

The depth of the root ball will depend entirely on the depth of the roots of the plant. If the roots are fibrous and plentiful in the top 12 inches of soil, you will only need to dig a few inches deeper than that. If the roots appear to be sparse and random, you should dig deep enough to include as many roots as possible. Once the depth seems satisfactory, start to taper in towards the center of the hole. The final root ball should have a "tea cup" shape.

Next, wrap the ball tightly with burlap. Feed the end of a long strip of burlap around the ball and wrap spirally, beginning at the trunk and ending at the base. Leave enough burlap at the end to pull under the ball when the plant is moved. Secure the burlap edges with pinning nails, available from most horticultural suppliers.

Now, remove the ball from the hole. Using the digging spade, carefully under-cut the root ball and gently roll the plant enough to pull the loose section of burlap underneath the root ball. Secure the ends of the burlap tightly with nails.

To get the plant out of the hole, cut a six-foot length of burlap to make a cradle for the plant. Carefully tilt the plant to one side and work the middle of the strip of burlap under the root ball. Two people can now lift the conifer from the hole and carry it to the new site.

If possible, orient the transplanted conifer in the same direction as it was at the old site to prevent sun-scald that can occur when a shaded side of a conifer is suddenly exposed to full sun. The aftercare for transplanted conifers is exactly the same as that for newly planted specimens.


Susan F. Martin has been Curator of Conifers at the U.S. National Arboretum, in Washington D.C. since 1979. She is a founding member of the American Conifer Society and a former editor of its quartetly bulletin.


Comments

May 29, 2010
Lynne Beverley Jenkins

Can conifer roots damage property if planted too close to houses and left to grow unattended to about 30ft?



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