How Does a Lilac Bush Grow?

Conditions

While weather conditions influence how long lilac blossoms remain in bloom, a lilac bush is basically a low-maintenance plant that can last for many years if properly cared for. Shrubs tend to thrive best in soil where there is adequate water drainage. Lilac bushes growing on a hillside or where the ground is slightly elevated seem to do best. Because the roots of the plant run deep, lilacs do not flourish if the soil around them becomes too wet and soggy. In fact, lilacs are hearty enough to survive periods of extremely dry weather if you keep the ground around them moist. Mounding mulch around the base of the plant is one way to help the soil retain moisture.

Lilacs can grow in just about any type of soil as long as the pH is slightly alkaline. Bushes should be fertilized early in the spring and then again immediately after the blooms have died off. Be careful not to overfertilize, and use a fertilizer that is high in phosphorous rather than nitrogen. Although the nitrogen content usually found in basic lawn fertilizers can make the leaves of a lilac plant greener, the bush is not likely to flower. Once lilac bushes come into bloom, the flowers last longer if the weather stays cool and dry.

Pruning

When a lilac tree grows taller and bushier, it begins to produce fewer flowers. Bushes should be pruned each year; however, the way you prune can determine the number of flowers that will bloom the next year. Never prune a lilac bush in the early spring, unless you don't want flowers that year. Likewise, do not prune bushes in late summer or in the fall, or you may not get any flowers the next year either. A general rule of thumb to follow is not to do any pruning after the first week in August. Instead, always prune lilac bushes within a week or two after the flowers die, as that is when new buds begin to form.

Begin by cutting off the dead blossoms. Pruning stems back to a leaf node keeps seeds from forming so that healthy flowers will bloom the following year. When a bush becomes too big, thin it out by removing one-third of the old growth. Cut large branches at ground level every year for 3 years to promote new growth out from the base. Some varieties of lilac grow 6 to 8 feet, but others can reach a height of 30 feet if not kept cut back. Use clippers rather than hedge trimmers to trim back the bush after the flowers have finished blooming. Trim larger stems from inside the trunk to allow sun in and more air to circulate. Cut new shoots off at the ground but leave a few young sprouts. Trim the top of the bush to look slightly rounded, but be careful how much you trim. If you cut too much off the top, you may not have flowers the next spring.

Transplanting

Early spring when the lilac is dormant is the best time to plant new shoots or transplant a bush. Lilac bushes can also be transplanted in the fall after the leaves drop. Mid-June tends to be a good time of year for planting lilacs, as they have a better chance of surviving if the weather is not too hot. Choose a location where the soil can drain adequately and the plant will get plenty of sunlight. Lilacs need lots of sun to bloom; therefore, bushes should not be planted in shady areas. Dig out several small shoots from the base of a lilac bush. Choose young shoots that are 1 or 2 feet tall. Try to get some root along with the shoots. Add compost to the soil before replanting. Plant several shoots together in one hole. New shoots usually take 2 to 3 years to root well, so it may be 3 or 4 years before a young plant develops enough to begin producing flowers.

If you transplant a mature lilac bush, dig the hole deep and wide. Get as much of a root ball as you can handle moving. The more root you can get, the greater the chance the bush will survive. Dig the new hole at least twice the width of the roots. Put some compost in the hole before setting in the plant. Try not to disturb or break the dirt from around the roots. After placing the bush in the ground, finish by filling in the hole with garden soil and more compost. The compost provides nutrients to the plant, especially if the weather gets dry. Pack the dirt down firmly around the bush. Keep the soil moistened but not too wet for at least 4 weeks or until the roots can take hold again.

Resources

• All About Lilacs