May Flowers: Lilacs
Lilacs are flowering shrubs and small trees in the genus Syringa, part of the olive family (Oleaceae). They are famous for their big clusters of sweet-smelling purple, lilac, pink or white flowers that bloom in spring, often in May, which is why they are classic “May flowers.”
Scientific Classification & Quick Facts
| Common name | Lilac |
| Scientific name | Syringa |
| Kingdom | Plantae |
| Phylum | Tracheophyta |
| Class | Magnoliopsida |
| Order | Lamiales |
| Family | Oleaceae |
| Type | Woody shrubs and small trees, 20 to 25 species |
| Habitat | Sunny, well-drained, neutral to alkaline soil |
| Native range | South-east Europe to eastern Asia |
| Flowering season | Spring |
| Height | 2 to 10 metres |
| Special feature | Fragrant flowers; name means blue |
Origins and Name
There are around 12 to 25 species of lilac, depending on how botanists count them. They grow wild in woodlands and scrub from southeastern Europe across to eastern Asia, and today they are grown in gardens throughout cooler parts of the world.
The scientific name Syringa comes from the Greek word syrinx, meaning a pipe or tube. Lilac stems have a soft, spongy center that could be hollowed out to make simple pipes and flutes. The English word “lilac” comes from the Persian and Arabic words lilak and laylak, which referred to the plant’s bluish color. Lilacs were grown in the gardens of the Ottoman Empire, in what is now Turkey, and were brought from there to western Europe in the 1500s. The French naturalist Pierre Belon was one of the first Europeans to describe them.
What Lilacs Look Like
Lilacs range from compact shrubs about 6 feet (2 meters) tall to small trees up to about 30 feet (10 meters). The trunks can reach about 8 to 12 inches (20 to 30 cm) across. The leaves grow in opposite pairs and are usually heart-shaped or broad and pointed.
Each tiny flower is only about a quarter to half an inch (5 to 10 mm) wide, with a narrow tube that opens into four petal-like lobes. Hundreds of these flowers grow together in cone-shaped clusters called panicles. Each flower has both male and female parts. Some lilacs grow tall enough to look like a small tree, and you can read more on our lilac tree page.
How to Grow Lilacs
Photo by: Wouter Hagens
Choosing a Spot
Lilacs need plenty of room. A single shrub may need 8 to 10 feet of space, so check the size of your variety before planting. For lots of flowers, give them at least 6 hours of full sun a day. They like fertile, well-drained soil that is neutral to slightly alkaline, with a pH around 7.0. If a soil test shows your soil is acidic, adding garden lime can help. Lilacs hate soggy roots and will not bloom well in waterlogged ground.
Planting
- Plant in fall or early spring. Fall planting gives roots time to settle in before the next spring.
- Mix compost into poor soil before planting to add nutrients and improve drainage.
- Dig a hole wider than the root ball and about as deep. Set the plant at the same depth it grew in the nursery pot.
- If the roots are wrapped in burlap or twine made of jute or hemp, remove it before planting. Gently loosen roots that are circling the pot.
- Fill in with soil, water well, then add more soil if it settles.
- Space shrubs about 5 to 15 feet apart, depending on the variety.
Placement and Watering
Larger lilacs make great hedges, screens and backdrops for shorter plants. Water young lilacs regularly during their first summer, especially in dry spells. Once established, they need watering only during long dry periods. Too much water and too much fertilizer can mean lots of leaves but few flowers.
By the way, lilacs are sometimes confused with lilies because the names sound alike, but they are completely different plants. Lilies grow from bulbs, while lilacs are woody shrubs.
When Lilacs Bloom
Common lilacs bloom in spring, usually from April to May depending on how far north you live. In the coldest parts of the northern US, such as USDA zones 3 and 4, they may not bloom until late May or around Memorial Day. By planting early, mid-season and late varieties, you can enjoy lilac flowers for several weeks. The Japanese tree lilac is one of the last to bloom, flowering in early summer with creamy white flowers.
After-Bloom Care
Lilacs form next year’s flower buds on this year’s growth soon after they finish blooming. That means the best time to prune is right after the flowers fade. If you prune in late summer, fall or winter, you will cut off next spring’s flowers.
- Snip off faded flower clusters to keep plants tidy.
- Remove a few of the oldest, thickest stems at ground level every year to keep the shrub young and full of flowers.
- Cut away suckers (shoots growing up from the roots) unless you want the plant to spread.
- Spread a layer of compost around the base each year.
Lilacs as Cut Flowers
Photo by: Kurt Stüber · Photo by: Wouter Hagens
Photo by: Kurt Stüber
Lilacs bring their lovely scent indoors, but their woody stems need a little care or the flowers will wilt within hours.
- Cut stems in the cool of early morning, choosing clusters with about half their flowers open.
- Strip off most of the leaves, which pull water away from the flowers.
- Recut the stem ends at an angle and make a short vertical slit up the bottom of each stem to help it drink.
- Put the stems straight into a vase of fresh, room-temperature water and keep it topped up.
With good care, cut lilacs stay fresh for several days.
Lilac FAQs
Where do lilacs come from?
Lilacs are native to shrubby areas and woodland from south-east Europe to eastern Asia. They are now grown in temperate areas around the world.
How tall do lilacs grow?
Lilacs grow 2 to 10 metres tall, depending on the type. Many garden lilacs are about 10 feet tall.
Where does the name lilac come from?
The English name comes from the Persian or Arabic word for blue. The scientific name Syringa comes from the Greek word for a pipe, because the hollow stems were used to make flutes.
How much sun do lilacs need?
Lilacs need at least 6 hours of sun a day to flower well. They also need well-drained soil, because they dislike wet feet.
When should you prune lilacs?
Prune them right after they flower. Most lilacs bloom on the previous year’s growth, so pruning later removes next year’s flowers.
Randi Jones is the owner and founder of the Nature Gift Store, an online retailer specializing in nature-themed gifts, educational science projects, live animal nature kits and real butterfly artwork. A biology graduate who fell in love with insects, she founded the company in 2001 to make active learning about nature fun, accessible and engaging for children and adults. Her store offers real butterfly frames, home and garden decor and educational live animal kits, including ant farms, worm farms, tadpoles, ladybugs and hermit crabs, and she runs a bug museum in Washington featuring live animals like Eddie the Iguana alongside other reptiles and insects.
