When to trim lilacs?

Pruning Lilac Bushes: When To Trim Lilac Bushes

Who doesn’t enjoy the intense fragrance and beauty of lilacs? These old-fashioned favorites are wonderful additions to nearly any landscape. However, periodic pruning is vital in order to keep lilacs healthy and looking their best. Although there are smaller varieties, about ten to fifteen feet (3-4.5 m.), many lilacs can reach heights of about thirty feet (9 m.) tall without regular pruning. Pruning lilac trees on a regular basis keeps them from becoming too tall and unmanageable.

How to Prune Lilac Bushes

When pruning lilacs, cutting back the tops of overgrown stems is oftentimes not enough. It is generally better to cut the entire stem. Trimming lilacs is best accomplished using clippers. Remove spent blooms all the way to the stems to prevent seeding and encourage more blooms later on. Cut back about a third of the branches. Cut away shoots growing near the ground that may be sprouting from the main trunk. In order to improve air circulation or to allow more light to filter through, trimming lilacs within the inner branches may be necessary.

If lilac bushes are already too large or becoming unsightly, however, pruning the entire bush or tree to about six or eight inches off the ground may be necessary. Keep in mind that you may have to wait for flowers, as it takes about three years for them to develop once entire shrub has been cut.

When to Trim Lilac Bushes

Knowing when to trim lilac bushes is important. Most lilacs don’t require pruning until they reach about six to eight feet (2-2.5 m.) tall. The best time for pruning lilac bushes is right after their flowering has ceased. This allows new shoots plenty of time to develop the next season of blooms. Pruning lilacs too late can kill young developing buds.

If you are pruning lilac trees or shrubs entirely to within inches of the ground, it is best to do so in early spring. New shoots will develop during the regular growing season as long as there are a few healthy shoots left. Once the growing season has ended, remove any unsightly shoots.

Pruning lilac bushes is important for their health and flower production. Lilacs are generally pretty hardy and if proper pruning is performed, they will come back stronger than ever.

Pruning Large, Overgrown Lilacs

The common purple lilac is a tough, reliable shrub that may reach a height of 15 to 20 feet. Unfortunately, as lilacs mature, the shaded lower portions of the shrubs usually lose their leaves. As a result, large, overgrown specimens are often leggy and unattractive. Old, neglected lilacs can be renewed or rejuvenated by pruning. Home gardeners can choose between two different pruning methods.

One way to renew a large, overgrown lilac is to cut the entire plant back to within 6 to 8 inches of the ground in late winter (March or early April). This severe pruning will induce a large number of shoots to develop during the growing season. In late winter of the following year, select and retain several strong, healthy shoots to form the shrub framework and remove all the others at ground level. Head (cut) back the retained shoots to just above a bud to encourage branching.

A second way to prune old lilacs is to cut back the overgrown shrubs over a three-year period. Begin the procedure by removing one-third of the large, old stems at ground level in late winter. The following year (again in late winter), prune out one-half of the remaining old stems. Also, thin out some of the new growth. Retain several well-spaced, vigorous stems and remove all the others. Finally, remove all of the remaining old wood in late winter of the third year. Additional thinning of the new shoots should also be done. Since lilac wood needs to be 3 or more years of age before it blooms, this pruning method should allow you to enjoy flowers every spring.

When properly pruned, an old, overgrown lilac can be transformed into a vigorous attractive shrub within a few years. Once rejuvenated, pruning should be a regular part of the maintenance program for lilacs. The shrub can be kept healthy and vigorous by removing a few of the oldest branches every 3 to 5 years.-

This article originally appeared in the February 10, 1993 issue, p. 8.


Syringa vulgaris ‘Sensation’ 1

What other plant captivates your senses and evokes fond memories of springtime more than lilacs? The intense fragrance of their large, beautiful flowers and their relative ease of care, make lilacs treasured throughout the temperate world. They bring us a few weeks of fabulous color and fragrance each year, but their loveliness and charm leave lifetime memories.


Syringa meyeri ‘Palibin’ lilac is considered one of the best dwarf lilacs on the market.1

Lilacs (Syringa spp.) come in all different shapes and sizes from dwarf forms only 4 to 5 feet tall, to lilac trees, 25 to 30 feet tall. Lilacs can be mixed in the border with other deciduous shrubs, conifers, herbaceous perennials, bulbs, ground covers and annuals to extend and enhance the season of color.

Tree lilacs make terrific, urban-tolerant street trees, which offer shade on hot summer days. Smaller, slower-growing lilacs are perfect for most residential landscapes. They can be used in shrub beds or as foundation plants. They can also be planted in containers and placed on decks and patios. Lilacs tolerate very cold winters, hot summers, humidity and almost any well-drained soil. They do require full sun for good flower bud set.

Care of Lilacs

Lilacs require at least six hours of direct sunlight a day during the growing season to properly set flower buds for the following spring. The amount of sunlight determines the plant’s appearance and quantity of flowers. Lilacs planted in too much shade will either flower poorly or not at all. Do not crowd lilacs because they will grow tall and leggy with sparse flowering. The planting site should be large enough to accommodate the full-grown root system and the mature height and spread of the plant.

Some lilacs are prone to diseases, especially powdery mildew, which appears as white powder on the leaves. Spores of the fungus are most active when the weather is hot and humid and the air is stagnant. Certain species and cultivars of lilac are more susceptible than others to powdery mildew. It is important when selecting and planting lilacs to choose resistant varieties and plant them in full sun with good air flow to minimize these disease.

Lilacs are tolerant of a wide range of pH and soil conditions, but require good drainage. Poorly drained soil will result in little growth, poor flowering and gradual deterioration. This decline occurs over several years. If the soil is poorly drained, consider improving it with the addition of topsoil or organic matter (peat, composted leaf mulch or compost) to the planting hole or plant in raised beds with good soil.

Water and Fertilizer

Newly planted lilacs should be watered two to three times a week for the first month. After the first month, they should be watered deeply once a week. During periods of hot, dry weather, watering may need to be done more frequently. Most trees and shrubs benefit from 1 inch of water a week during the growing season, but do not over water lilacs because root diseases may develop.

Do not fertilize newly planted lilacs. Plants first need to establish a developed root system to support further growth. After this time, perhaps for two or three years, fertilization may be needed if the plant does not begin to grow more vigorously. A soil test should be performed to determine if phosphorus (P) and potassium (K) are limited. If so, a complete fertilizer such as 5-10-5 or 10-10-10 may be applied at the base of the plant, following labeled application rates. Do not over fertilize or use fertilizers containing high levels of nitrogen (N). This can cause excessive shoot and foliage growth at the expense of flower bud development. Apply any necessary fertilizer after the spring- flowering period.

Add a 2-to-3 inch layer of loose mulch around the base of the plant to help retain the soil moisture, keep the roots cool and suppress weed development. Take care to keep the mulch away from the trunk of the tree or basal portions of shrub stems to enable good air circulation. Otherwise, disease infections, pest infestations and damage by rodents may occur where the mulch is piled to closely to the bark.

Pruning

Pruning lilacs will depend on bloom period, growth pattern and location. Newly planted lilacs will not need much pruning for the first two to three years. Established lilacs are usually best pruned during the late dormant season, typically March or early April. This time of year allows for ease in pruning because you can see what you are doing, there is less insect and disease activity and pruning wounds close more quickly with the onset of spring growth. However, pruning at this time will sacrifice some display because you are removing flower buds. Pruning can also be done immediately after flowering, if you do not want to sacrifice any blooms. However, if you wait too long into the summer to prune, you will remove next year’s flower buds.


Syringa vulgaris ‘Frederick Law Olmstead’ 1

Lilacs that sucker readily, such as common and early lilacs (S. vulgaris and S. xhyacinthiflora) should receive renewal pruning about every two to three years. Older, larger diameter branches tend to have reduced vigor and produce fewer flowers concentrated mainly at the tops of the branches – too tall to enjoy their beauty or fragrance. Larger branches are also more prone to lilac borer infestation at their base. This insect makes its way into the branch cambium and wood. As the insect eats the wood, the branch becomes weaker, leaves yellow and the branch begins to die. Few, if any, flowers are produced the following years. The best way to control this insect pest is to periodically cut the infested, weakened branches out.

Renewal pruning involves removal of around one-third of the largest diameter branches down to ground level with a pruning saw or loppers. Removal of these larger branches greater than 1  inch in diameter promotes new shoot development at the base of the plant.

Renewal pruning allows the lilac to continue to flower vigorously each year and maintains the size of the plant. Vigorous young growth generally produces larger and more numerous flowers compared to the older, larger diameter branches.

Prompt deadheading of faded blooms will improve a plant’s appearance and help the lilac concentrate its energy into flower bud formation and not on seed production. For smaller lilacs that do not sucker, renewal—pruning is unnecessary, only annual shaping of the plant may be needed.

For those interested in learning more about lilacs, consider joining the International Lilac Society (ILS) at internationallilacsociety.org.

Sampler of small to medium-sized lilacs for home gardens and containers. Most of these bloom mid- to late May.
Syringax hyacinthiflora: early flowering lilac in early May, suckering, hardy to Zone 3a
‘Declaration’: single dark reddish-purple flowers 7 to 8 ft. tall, 6 to 7 ft. wide, deep burgundy fall color hardy to Zone 4b*
‘Excel’: single, bluish-pink to lilac-lavender flowers; 6 to 8 ft. tall and wide; burgundy-red fall color*
’Sister Justina’: single, pure white flowers; 8 ft. tall and wide*
Syringa oblatavars. dilatata ‘Cheyenne’: early Korean lilac with single, light blue flowers in early May: 6 to 8 ft. tall, 8 to 10 ft. wide; suckering; burgundy-red fall color; hardy to Zone 3a*
Syringa FairytaleSeries®: 4 to 6 ft. tall, 5 to 6 ft. wide; nonsuckering; hardy to Zone 5a and can rebloom sporadically in summer
‘Bailbelle’ Tinkerbelle®: single, deep pink flowers fading to medium pink*
‘Bailina’ Thumbelina®: single, light pink flowers fading to white*
‘Bailming’ Prince Charming®: single, reddish-purple flowers fading to lavender-pink*
‘Bailsugar’ Sugar Plum Fairy®: single, rosy-lilac pink flowers*
‘Josée’ (S. ‘MORjos 060F ‘): single, light lavender pink to deep rose flowers fading to a lighter rose color; can rebloom sporadically in summer; 4 to 6 ft. tall, 5 to 6 ft. wide; non-suckering, hardy to Zone 4a*
Syringax laciniata, cutleaf lilac: single, light lavender flowers; 5 to 6 ft. tall, 8 to 10 ft. wide; suckering; hardy to Zone 4b*
Syringa meyeri ‘Palibin’: single, dark pinkish to light purple flowers; can rebloom sporadically in summer; 4 to 5 ft. tall, 5 to 6 ft. wide; nonsuckering; maroon-purple fall color; hardy to Zone 4a*
Syringa pubescens subsp. julianae, Juliana lilac: nonsuckering, hardy to Zone 3b
‘George Eastman’: bright reddish-pink flowers fading to lighter pink, 6 to 8 ft. tall and wide*
‘Hers’: single, lavender to pinkish flowers; semi-weeping form; 5 to 6 ft. tall, 10 to 12 ft. wide*
‘Karen’: single, fragrant, white to soft light pink flowers; 5 to 6 ft. tall and wide*
Syringa pubescens subsp. microphylla ‘Superba’: single, rosy-pink flowers fading to lighter pink flowers; can rebloom sporadically in summer; 5 to 7 ft. tall, 8 to 10 ft. wide; nonsuckering, hardy to Zone 5a*
Syringa pubescens subsp. patula ‘Miss Kim’: single, light lilac-violet to lavender flowers; 6 to 8 ft. tall and wide; nonsuckering; burgundy fall color; hardy to Zone 3b*


Syringa pubescens subsp. patula ‘Miss Kim’ 1

Syringa ‘Red Pixie’: single, dark reddish-pink to magenta flowers fading to light pink; can rebloom sporadically in summer; 4 to 6 ft. tall, 5 to 6 ft. wide; nonsuckering, hardy to Zone 4a*
Syringa vulgaris: common lilac, suckering, all hardy to Zone 3a
‘Albert F. Holden’: single, deep violet to purple flowers; 6 to 8 ft. tall and 8 ft. wide
‘Alvan R. Grant’: single, purple, cupped flowers; 6 to 8 ft. tall and wide
‘Arch McKean’: single, dark reddish-purple to dark magenta flowers; 8 ft. tall and wide; fewer suckers*
‘Fiala Remembrance’: double, satiny, creamy-white flowers; 6 to 8 ft. tall, 8 ft. wide; fewer suckers*
‘Flower City’: single, deep violet-purple, cupped flowers; 8 ft. tall and wide*
‘Frederick Law Olmsted’: single, satiny, white flowers; 5 to 7 ft. tall and wide*
‘Lucie Baltet’: single, light coral pink flowers; 6 to 8 ft. tall, 8 ft. wide*
‘Marie Frances’: single, pink flowers; 6 to 8 ft. tall and wide*
‘Prairie Petite’: smaller, single, lavender-purple flowers; very compact; 3 to 4 ft. tall and wide
‘Rochester’: single, creamy-white, multi-petaled flowers; 6 to 8 ft. tall, 8 to 10 ft. wide*
‘Wedgwood Blue’: single, Wedgwood blue flowers; 8 ft. tall, 6 to 8 ft. wide
‘Wonderblue’, aka ‘Little Boy Blue’: single, sky-blue flowers; 5 to 6 ft. tall and wide*
‘Yankee Doodle’: single, large, very dark purple flowers; 6 to 8 fet tall and wide


Syringa vulgaris ‘Yankee Doodle’ 1

Syringa vulgaris ‘Wonderblue’ 2

Syringa (Villosae Group) ‘Minuet’: flowers in late May to early June; single, light lavender-purple flowers; 6 to 7 ft. tall, 4 to 6 ft. wide; nonsuckering, hardy to Zone 3b*
*Indicates resistant to powdery mildew.

PHOTO CREDIT:

1. Photo courtesy of Laura G. Jull.
2. Photo courtesy of Knight Hollow Nursery.

From State-by-State Gardening May/June 2013.

Havet

We just moved into a new home, and I am trying to get the yard ready for winter. The front yard has black plastic down and bark all over, even under the lilac bushes. The lilac bushes are overgrown, and it is hard to get under them to get the plastic and the bark out. I was wondering if it is okay to prune them in the fall and, if so, how much is too much to prune back? This is the first time that I have had a yard, so I don’t know a whole lot.

Sandra Lake

Dear Sandra,
The best time — and only correct time, really — to prune lilacs is just after blooming. All shrubs fall into one of two categories; some, like many of the hydrangeas, bloom exclusively on new wood and can be pruned to the ground each fall if required. Others, such as lilacs, bloom only on old wood from the previous season. Thus, if you prune at any time other than immediately after flowering, you will cut off next year’s blooms. For lilacs, the recommended method is generally to remove one third of the old wood each year immediately after flowering and shape the shrub over a number of seasons. Of course, you can prune in the fall if absolutely required. Keep in mind, though, that you are cutting off all of next spring’s luscious blossoms in the process.

How to Keep Lilacs from Wilting in a Vase

If you’re hosting a party or just want to bring a little bit of life indoors, it’s easy to just clip a few sprigs of lilacs off the bush in your yard and plop them in a vase of water. Sometimes it just doesn’t feel worth the effort when they end up looking wilted and dead by the end of the day. With the right techniques and care, you can keep your lilacs upright and vibrant for days.

Image zoom Photo by Andy Lyons Andy Lyons

The best time to cut lilac blossoms is early in the morning when they’re fully hydrated. Cut the stems with sharp, clean pruning shears, then immediately plunge the cut stems into a bucket of water. Cut long stems for the longest vase-life. Indoors, get a vase ready for the flowers. Make sure it’s clean by running it through a dishwasher cycle or washing it by hand with a solution of 10 percent bleach and 90 percent water. Residue from soaps and past arrangements may harm the cut flowers.

Add fresh water and a floral preservative, which you can find at florist shops, to the vase. Remove all leaves that would be underwater in the vase, but leave the upper leaves intact for a fuller arrangement. Recut the stems at a 45-degree angle, and arrange the lilacs in the prepared container. Set the vase in indirect light and enjoy. Recut the stems, still keeping a 45-degree angle, and add more water as needed to prevent wilting.

How to Prune Lilacs. Fragrant, colorful lilacs are easy to grow in most regions. Whether your lilac is a shrub or a small tree, it will need to be. Trimming lilac bushes is similar to trimming fruit trees, as it is best to prune the bush into a bowl or vase shape to allow the innermost branches. To keep your lilacs looking their best, they need to be pruned, Your lilac bush should respond and fill in with lush, healthy new growth from.

Trimming lilac bushes is similar to trimming fruit trees, as it is best to prune the bush into a bowl or vase shape to allow the innermost branches. Lilacs are wonderful additions to nearly any landscape; however, periodic pruning is vital in order to keep lilacs healthy and looking their best. Q: What’s the best way to prune lilac bushes so they’ll bloom every year?.

To keep your lilacs looking their best, they need to be pruned, Your lilac bush should respond and fill in with lush, healthy new growth from. How to Prune Lilacs. Fragrant, colorful lilacs are easy to grow in most regions. Whether your lilac is a shrub or a small tree, it will need to be. How and when you prune your lilac bushes has a direct impact on the number and size of springtime blooms. This article tells you everything.

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