Winterizing Lilac Shrubs: Tips For Lilac Care In Winter
By: Bonnie L. Grant, Certified Urban Agriculturist
Lilacs are superior performers when it comes to blooming. They develop buds in the fall which overwinter and burst into color and scent in spring. Winter freezes can damage some tender varieties but the majority of lilac cultivars are hardy to United States Department of Agriculture zones 4 or even 3. With good pruning practices and some spring babying, the plants handle a hard winter beautifully and need little special lilac care in winter.
Winterizing Lilac Shrubs
Lilacs are one of the most winter hardy ornamental plants around. Do lilacs need cold protection? They can withstand temperatures of -40 degrees Fahrenheit (-40 C) but may need some protection from icy winds that damage the flower buds. They need well-draining soil to prevent frozen water from damaging their roots and killing the tree. Lilacs that have not been grafted are hardier than those that have been grafted to rootstock.
Lilac winter care starts with good siting and a healthy plant. The plant needs at least 8 hours of sunshine and alkaline to neutral soil. When choosing a planting location, avoid planting them against a light colored building or wall, as this can cause winter burn from the reflection.
They make a brilliant front of house display and darker buildings can actually afford lilac winter protection. However, avoid planting them too close to the foundation, as their roots can cause issues over time. Prune off the spent flower heads to help promote bud formation. Winterizing lilac shrubs is not the intensive process it is for sensitive plants.
Lilac Care in Winter
Lilacs withstand a chilly winter better than most plants. They do benefit from occasional watering if there is no precipitation available to the roots. Watering around the root zone actually keeps the soil warmer than dry soil, offering lilac winter protection.
In rare cases, you may need to cover the plant to protect the buds. This occurs in late winter to early spring when buds are beginning to break and a harsh freeze comes along. Use a blanket, canvas, or even plastic tent over the bush to help protect the buds form the cold. Remove it during the day if temperatures warm up so the plant can get sun and air.
Pruning for Post Lilac Winter Care
Pruning is not important for the first 5 to 6 years of a young lilacs life. It can be an important step to lilac recovery if winter damage has occurred. Wait until the plant has bloomed before you make any cuts to avoid removing the flowers.
Cut out any damaged or diseased stems. Thin the suckers by one-third for complete rejuvenation of old plants. After 3 years, the plant will be renewed without affecting bloom production.
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Read more about Lilac Bushes
Lilac Winter Care - Do Lilacs Need Cold Protection Over Winter - garden
Growing Lilacs is easy. They are a low-maintenance shrub. Lilacs offer good summer shade, after they have reached several feet tall. They can be used as a hedgerow, to provide privacy from neighboring properties. With just a little care and maintenance, the knowledge of growing Lilac bushes, and how to replenish the old wood with new shoots, lilac bushes last a lifetime.
Did You Know? Lilacs are members of the olive family.
Lilacs do not like to get their feet (the roots) wet for a prolonged period of time. They do best on hillsides, slightly elevated areas, or level ground where there is good drainage. Lilac roots run deep. If you have an extended dry period or drought, water infrequently but thoroughly. Lilacs do not grow well in lowlands, where water tends to collect for prolonged periods of time.
Weed around your lilac bushes to maintain a clean, aesthetic look. Pile mulch high around the plants, for a neat and tidy appearance, to retain some soil moisture, and to keep weeds down.
Caution: Do not make mulch so thick, that new shoots are hampered from sprouting and developing.
Lilacs will tolerate almost any kind of soil, from clay to sand, with a pH of 6.5 to 7. Like many plants, your Lilacs will benefit from compost and humus worked into the soil, to help retain some water during dry spells, and to provide nutrients.
Lilac bushes do not need a lot of fertilizer or organic feeding. Fertilize lilacs with a high Phosphorous formula in early spring, to promote blooming. Too much nitrogen in the soil, will result in poor blooms. Use a general purpose fertilizer in early summer.
Tip: Spread some fireplace ash around the drip line of your bush, for bigger and better blooms.
Flowers will bloom in May. Prior to blooming, fertilize with a high phosphorous fertilizer, and one that has little or no nitrogen. There are several causes for lack of blooms. See "Why No Blooms?"
If you want to prune lilacs, it is important to do so immediately after the blooms die off. Read important information on pruning lilacs.
The bushes are very susceptible to powdery mildew in hot, humid weather. This is evident by the appearance of a white, "powdery" substance on the leaves. Use fungicides before humid weather sets in. More on Diseases of Lilacs
Lilac Garden Tip: Invasive Lilac varieties aggressively send out runner shoots. If you have an invasive variety, we recommend garden edging to keep their spread under control.
Lilac are winter hardy. No special protection is needed. Cold winters help to promote blooms.
Buy Lilac Bushes select from popular Lilac varieties
Most lilacs are hardy in zones 3-8 however, there are varieties cold hardy to zone 2, like Scentara® Double Blue (S. hyacinthiflora). There are also varieties, like 'Lavender Lady' (S. vulgaris) that are heat tolerant to zone 9 and don't require a winter chill. Most others do require a cold, dormant period over winter.
The common lilac (Syringa vulgaris) grows 12 to 15 feet tall and 10 to 12 feet wide. There are many smaller dwarf varieties that mature at 4 to 6 feet tall and 3 to 7 feet wide. Japanese tree lilacs (Syringa reticulata) can reach 25 to 30 feet tall.
Lilacs need a minimum of 6 hours full sun for best flowering.
Most bloom in late May however there are early spring, mid spring, and late-season blooming varieties, as well as new re-blooming varieties, like the Bloomerang® series.
The common lilac (Syringa vulgaris) has purple blossoms, dark gray-green to blue-green foliage (with no fall color change), and gray to gray-brown bark. However, there are officially 7 colors of lilac flowers: white, violet, blue, lavender, pink, magenta and purple with many shades within each color.
California lilac, mountain lilac and wild lilac aren’t true lilacs, but actually belong to the genus Ceanothus. Summer lilac is often used to refer to butterfly bushes, especially those types that are sterile and non-invasive.
Consider removing the plant
- What is the value of the plant (property value or sentimental value)? There are many great plants including resistant lilacs that could be good replacements. You can find some of them in the Plant Elements of Design plant database.
- Is the lilac at the end of its life? Lilacs are relatively long-lived plants (25 years to 50+ years) depending on how they have been cared for and their growing conditions.
- What is the potential for spread to other plants of the same kind or another susceptible species?
- Can the issue be managed by other methods of management (pruning, sanitizing, improved plant care)?
- Do you need a certified arborist to assess the plant(s)?
- Has this problem occurred repeatedly for multiple years? Have different methods of management failed?
Lilac Pseudocercospora Leaf Spot. Horticulture and Home Pest News. Iowa State University Extension and Outreach. Accessed Aug. 28, 2020.
Julie Weisenhorn, Extension horticulture educator, and Grace Anderson, Extension Master Gardener, research scientist and diagnostician, UMN Plant Disease Clinic
Can Lilacs Be Grown Indoors?
Smaller lilac plants, such as our Bloomerang® Dwarf Pink Lilac, can thrive in containers. Appropriate care of potted lilac plants is important. Place it in a south facing window that receives at least 6 hours of full sun every day. More than likely lilacs won't "thrive" indoors, but they can survive if given enough sunlight. Keep the lilac relatively moist, watering every time the soil dries out to an inch below the surface. If the roots are restricted, the plants will not flower or have proper growth. It is important to cut back the roots when they grow beyond the size of the container.
Q. Why Do Lilac Bushes Change Shades of Color Some Years?
We moved into our home 5 years ago. I was so excited about our BEAUTIFUL Lilic bush when it bloomed light purple blooms all over. This year something REALLY amazing happened. It bloomed deep purple blooms. The bush is about 9-10 feet tall and about 4-5 feet wide. It's got deep purple blossoms everywhere! It's awesome! Why would the bush change color this year?
It is possible for a lilac to have a different hue from one year to the next, depending on pH, moisture and nutrition. While one cannot change the color in a lilac as one could with some of the hydrangea, hue changes are definitely a possibility.