If you’ve noticed your lilac leaves curling, it’s a clear signal from your shrub that something isn’t quite right. This common symptom can point to several issues, from pests to environmental stress. Don’t worry, though—curling leaves are often a solvable problem once you identify the cause. Let’s look at the most common reasons and how you can help your lilac recover its health and beauty.
Lilacs are generally tough plants, but they’re not immune to trouble. Curling leaves can affect their ability to photosynthesize, weakening the plant over time. By understanding the signs, you can take targeted action.
Lilac Leaves Curling
This specific symptom is your starting point for diagnosis. The way the leaves curl—upward, downward, or in a twisted manner—often gives you the first clue about what’s going on. Pay close attention to other details too, like color changes or the presence of insects.
Common Causes of Curled Lilac Leaves
Here are the primary culprits behind those curling leaves. You’ll likely recognize one of these scenarios in your garden.
1. Lilac Leafminers (The Most Likely Suspect)
This tiny moth is a frequent cause of leaf curl in lilacs. The adult moth lays eggs on the underside of leaves. When the larvae hatch, they burrow inside the leaf tissue, feeding as they go.
You’ll see the damage in stages:
* Early signs are blotchy, light green patches on the upper leaf surface.
* As the larvae grow, the leaf begins to curl upward, forming a sort of loose tube or roll.
* Eventually, the affected area turns brown and brittle.
2. Aphid Infestations
These small, soft-bodied insects cluster on new growth and the undersides of leaves. They suck sap from the plant, which causes stress.
Signs of aphids include:
* Leaves curling downward or becoming distorted.
* A sticky residue called “honeydew” on the leaves.
* Sooty mold, a black fungus, growing on the honeydew.
* You can often see the aphids themselves—they can be green, black, or brown.
3. Water Stress: Too Much or Too Little
Lilacs prefer well-drained soil and don’t like “wet feet.” Both drought and overwatering can cause leaves to curl.
* Underwatering: Leaves may curl upward or inward to conserve moisture. They might also feel dry and crispy.
* Overwatering: Roots suffocate in soggy soil, leading to root rot. The leaves may curl, turn yellow, and drop. The plant looks wilted even though the soil is wet.
4. Herbicide or Chemical Damage
Sometimes, curling leaves are an accident. Drift from weed killers used on lawns or nearby gardens can affect lilacs. Even some fungicides applied in hot weather can cause a reaction.
Look for:
* Sudden, widespread curling or twisting of new growth.
* Leaves may have a cupped or strapped appearance.
* The pattern often effects the side of the plant facing where the chemical was applied.
5. Environmental Stress
Harsh weather conditions can take a toll. Strong, drying winds can cause leaves to curl and brown at the edges. Extreme heat waves, especially if combined with inadequate water, will also stress the plant.
6. Powdery Mildew (A Secondary Issue)
While this fungal disease is famous for its white, powdery coating on leaves, severe cases can also lead to leaf curling, distortion, and premature droping. It’s more common in late summer and in plants with poor air circulation.
How to Diagnose Your Lilac
Follow these steps to figure out what’s bothering your shrub.
1. Inspect the Leaves. Carefully turn leaves over. Look for tiny insects, webbing, or unusual markings. Note the curl direction.
2. Check the Soil. Dig a few inches near the root zone. Is it bone dry or swampy? Lilacs like moisture but need good drainage.
3. Review Your Care. Have you recently sprayed any chemicals? Has the weather been exceptionally windy, hot, or dry?
4. Look at the Whole Plant. Is the curling on one branch, one side, or all over? This clues you into whether it’s a localized pest or a cultural issue like watering.
Step-by-Step Solutions and Treatment
Once you’ve identified the likely cause, use these targeted treatments.
For Lilac Leafminers:
* Early Season: Prune off and destroy visibly curled leaves in spring. This removes the larvae before they become adults.
* Leaf Cleanup: In fall, rake and remove all fallen leaves from around the plant to disrupt the moth’s life cycle.
* Chemical Control: For severe infestations, an application of horticultural oil in early spring (before buds break) can smother overwintering pupae. Insecticidal soaps can help if timed correctly when larvae are active.
For Aphids:
* Blast Them Off: A strong jet of water from your hose can dislodge many aphids. Do this in the morning so leaves dry by evening.
* Encourage Beneficials: Ladybugs and lacewings love to eat aphids. Plant flowers like daisies or yarrow to attract them.
* Use Insecticidal Soap: Spray directly on the aphids, covering the undersides of leaves. You may need a few applications.
For Water Stress:
* Establish a Watering Routine: Water deeply at the base of the plant, providing about an inch of water per week during dry spells. Let the soil dry slightly between waterings.
* Improve Drainage: If the area is constantly wet, consider amending the soil with compost or even transplanting the lilac to a better spot in fall.
* Add Mulch: Apply a 2-3 inch layer of wood chip mulch around the base (not touching the stem) to help retain soil moisture and regulate temperature.
For Chemical Damage:
* Flush the Soil: Water the plant deeply to help dilute any herbicide that may have reached the roots.
* Prune Damage: Carefully prune out severely distorted growth.
* Provide Support: Keep the plant healthy with proper water and a light feed of balanced fertilizer to encourage new, healthy growth.
For General Health & Prevention
* Prune Correctly: Lilacs bloom on old wood. Prune them right after flowering finishes to improve air circulation and shape the plant without sacrificing next year’s blooms.
* Fertilize Lightly: In early spring, you can apply a balanced, slow-release fertilizer or compost around the drip line. Avoid high-nitrogen fertilizers, which can promote leafy growth susceptible to pests.
* Choose Resistant Varieties: If powdery mildew is a recurring issue, consider planting resistant cultivars like ‘Miss Kim’ or ‘Bloomerang’ in the future.
Frequently Asked Questions (FAQ)
Q: Why are my lilac leaves curling and turning brown?
A: This combo often points to leafminers (where the mined area browns), severe water stress (drought scorch), or possibly chemical burn. Check for insect activity inside the curled leaves first.
Q: Can curled lilac leaves recover?
A: It depends. Leaves severely damaged by leafminers or herbicides will likely not flatten back out. The goal is to protect the new growth. With proper care, your lilac will produce healthy new leaves. Prune away the badly damaged ones.
Q: Is lilac leaf curl contagious to other plants?
A: The leafminer moth specifically targets lilacs and privet. Aphids can move to other plants, but the curling symptom itself is not a disease that spreads. Still, it’s wise to check plants nearby for pests.
Q: Should I fertilize my lilac if the leaves are curling?
A: Hold off until you diagnose the problem. Fertilizing a stressed plant, especially one with root issues, can add more stress. Address the primary cause of the curl first, then consider a gentle feed later to support recovery.
Q: When is the best time to treat for lilac pests?
A: Timing is crucial. For leafminers, physical removal of curled leaves in late spring and fall cleanup are key. For aphids, treat when you first see them. Dormant oil applications for overwintering pests should be done in late winter or very early spring before buds swell.
Seeing your lilac leaves curling can be concerning, but it’s rarely a death sentence for the plant. Start with a careful inspection, match the symptoms to the cause, and take the approriate action. Often, simple steps like adjusting your watering, pruning affected growth, or encouraging natural predators can make a huge difference. With a little attention, your lilac can bounce back, ready to fill your garden with its wonderful fragrance once again.