Winter is a dangerous time for plants, including lilac bushes. You’ll want to protect your lilac bushes during the winter so that you can continue to enjoy the bright purple blooms for years. If you live in an area with harsh winter conditions, you’ll need to take precautions to protect your lilac bush.
Lilacs should be covered before frost because the freezing conditions can damage flower buds that have not yet bloomed. To what extent you should cover your lilacs varies depending on your USDA Plant Hardiness Zone.
In the rest of this article, I’ll discuss how to care for these beautiful plants in winter conditions, including frost. If you’d like to incorporate lilac bushes into your yard or garden, but you live in a cold area and have some concerns, keep reading to get your questions answered.
How the Frost Affects Lilacs
Lilacs are cold-hardy plants, so it is unlikely that a frost will completely kill the whole plant. However, if the flower buds on the plant are just about to open, a frost could kill these buds, and you won’t see flowers until next year.
In this scenario, there is no way to fix the buds or bring them back to life. You’ll just have to wait to see that gorgeous purple color in your yard again.
For more about lilacs in winter, check out my other article: Do Lilacs Lose Their Leaves in the Winter?
If you know a frost is coming, you can cover your plant to protect it. Whether you should permanently cover the plants in burlap or temporarily cover them with wood depends on where you live according to the USDA Plant Hardiness Zone.
This system uses the average annual minimum winter temperature to outline ten different zones across the country. Each zone has different plants that are likely to thrive in the zone.
Lilacs grow best in USDA zones three through seven. If you do happen to live in a USDA zone higher than seven, it is unlikely that you’ll have to cover your lilac plant long-term because frosts will be rare. In this situation, a temporary wood covering will suffice. After the frost is over, you can easily remove the wood covering to allow your lilacs to access the sunshine they need.
However, if you live in a USDA zone seven or lower, you should consider covering your lilac plant long-term with burlap. The long-term covering is not ideal in areas where the weather fluctuates because these conditions foster mold growth. Lilacs are prone to fungal diseases, so they could suffer lasting damage if mold does grow.
If you find mold or powdery mildew on your lilac plant, prune the branches with infected leaves and throw them away or burn them. Then, cover the leaves with an insecticide spray. I recommend using neem oil spray, as it is organic and gentle enough for use on plants with flowers. It helps prevent pests and controls powdery mildew, mold, blackspot, botrytis, and downy mildew.
If you live in an area that has extremely harsh winters with icy winds and heavy snowfall, covering your lilacs with burlap is worth the risk of mold.
Keep the following steps in mind for the best results:
- Wrap the burlap around the plant, lifting the branches as you go to avoid accumulating snow.
- Overlap the layers of the burlap to provide more warmth and protection.
- Leave the top of the plant exposed.
- Use twine to secure the burlap in place.
- Throughout the winter, check the burlap regularly to ensure it is still protecting the plant and hasn’t been ruined by strong winds or heavy snow.
- If snow or ice accumulates on top of the plant, brush it away gently.
As soon as winter is over and there isn’t a risk of frost or other harsh winter conditions, you can remove the burlap to prevent fungi growth.
How to Prepare Lilacs for Winter
Covering your lilacs with a temporary wood covering or long-term with burlap is not the only way to help them survive the winter.
Here are some more ways to winterize lilacs:
Make Sure That Your Lilac Plant Is in an Optimal Location
Lilacs need a lot of sunshine, so you should avoid planting them against a light-colored building. In the winter, this proximity can cause winter burn on the plant.
Cover the Base of the Plant With Mulch
Sometimes, roots can become exposed during the winter and suffer damage due to repeated freezing and thawing. To prevent this, add three or four inches (7.62-10.16 cm) of mulch to the base. Check this mulch regularly to ensure that it hasn’t been blown away, and replace it as needed.
Prune the lilacs after they’ve completed their spring blooming. Pruning lilac plants can help them endure a harsh winter and encourage recovery if they suffer damage.
For more information on how to cut back a lilac plant successfully, you can read my other articles: Can You Cut a Lilac Bush to the Ground? or If You Cut Lilacs Will They Grow Back?
Water Lilac Plants Before the Ground Freezes
One of the biggest problems lilacs face during winter is dehydration, so it is essential to get them off to a strong start to the season by watering them with two or three gallons (7.6 – 11.4 liters) of water before the first freeze.
After this, you won’t need to water your lilac plants frequently, although a little bit of water around the roots every once in a while is a good idea.
No matter what, you should fight the urge to bring lilac plants inside for the winter. These are sturdy plants that can survive outside, and the cold temperatures help set the buds for future growth. If winters in your area are extremely harsh, add more mulch around the roots to protect them.
How to Encourage Lilacs to Flower
Allowing your lilac plants to endure the cold temperatures helps foster future flowering, but it isn’t the only thing you can do.
Here are my suggestions for how to get lilacs to flower:
Make Sure You’re Pruning at the Right Time
If you cut back a lilac plant too early or too late, you risk damaging the flower buds that would have bloomed into flowers in the future.
For more on this, check out this article: How Late is Too Late to Prune Lilacs?
Plant Your Lilacs in a Location That Gets Lots of Sunlight
Lilacs are full-sun plants, so they need at least six hours of sunlight each day. If your plant isn’t flowering, you may need to move it to a sunnier spot. While this works for potted lilacs, it can be challenging for ground-planted ones. Therefore, it’s crucial to plan your lilac’s location before planting.
Add Phosphorus to the Soil
Phosphorus helps encourage flower growth, boost the development of flowers, and encourage bigger blooms. You can buy phosphorous-rich fertilizers from your local garden center or online.
Pour a Water-And-Epsom Salt Solution Onto the Plants
Mixing a gallon (3.8 L) of water with two ounces (56.7 grams) of Epsom salt and then pouring this liquid on lilac plants is believed to help them emerge from dormancy.
With the right amount of care and attention, you’ll have lilac plants that bloom consistently and beautifully, year after year.
Conclusion
Lilacs should be covered before the frost because the harsh cold can damage flower buds. In USDA zones seven and below, a long-term burlap covering is appropriate. In USDA zones above seven, a temporary wood covering during the frost will suffice, and you can remove it as soon as the frost melts.
