Lilac
Syringa vulgaris
Six hours of sun or no bloom worth the name — and the pruning window closes the moment the flowers fade.
- Type
- Shrub · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Flower color
- Purple and violet
- Sunlight
- Full sun is essential — at least six hours for a good bloom.
- Watering
- Water it into the ground; drought-tolerant once settled.
- Feeding
- A compost mulch in spring, and bone meal after flowering.
- Frost tolerant
- Yes
- Flowering
- May
- Pruning
- Prune as soon as flowering ends, and take the suckers off grafted plants.
- Mar–May Bud Break
- May–Jun Flowering
- Jun–Oct Growing
- Oct–Dec Leaf Fall
- Jan–Mar Leaf Fall
- Plant spacing
- 9 ft 10 in
- In-row spacing
- 9 ft 10 in
- Between rows
- 12 ft 4 in
- Square-foot density
- Not suited to SFG
- Root system
- Woody and fibrous
- Working depth
- 12–24 in
- Can reach
- 3 ft down where the soil allows
- Spread
- 15–20 ft across, about 1.5–2× the width of the plant
- Shallowest pot
- 20 in of soil
A shallow woody framework with the fine feeding roots in the leaf litter above it. Those feeders are mostly under the outer half of the canopy rather than against the stem, which is where water and feed should go.
It suckers from the base steadily, and on a grafted plant those suckers are the rootstock rather than the named variety. Take them off at the root each year.
The habit is Lilac’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- Leaf miners Larvae that tunnel pale wandering trails or blotches inside the leaf itself. Pick off and destroy mined leaves; damage is usually cosmetic.
- Scale insects Immobile brown or white bumps fixed to stems and leaf undersides, sucking sap and weakening growth. Wipe off with a damp cloth or dab with horticultural soap; watch for the sooty mold that follows.
- Blight Lilac blight
- Powdery mildew A white dusty coating over leaves and shoots when roots are dry but the air is humid. Keep plants watered and mulched, prune for airflow, and remove the worst leaves.
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Hoverfly SyrphidaeHunts Scale insects
Bee-mimicking flies whose legless larvae graze aphid colonies clean while the adults pollinate. A ribbon of shallow, nectar-rich flowers kept in bloom all season recruits wave after wave of them.
- Ladybird (lady beetle) CoccinellidaeHunts Scale insects
The gardener’s favorite ally: adults and their alligator-shaped larvae each eat thousands of aphids, plus scale, mealybugs, and other soft-bodied sap-suckers. Grow flat, open flowers for the adults and never spray a colony that ladybird larvae are already working.
- Parasitic wasps Braconidae & TrichogrammaHunts Leaf miners
Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled.
Peonies, Iris, Geraniums, Roses
Shrubs, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com