Lilacs: Tips on planting and growing

The unique scent and beautiful flowers of a Lilac bush are a welcome sign of spring. This relatively care-free shrub is a beautiful addition to nearly any home landscape.

lilac bush in bloom Lilacs are ubiquitous in New England in the spring, great in landscapes as well as cut in vases.  They are an historic plant, found around many old homes and even surviving around old foundations after the home has fallen down.  They are easy to grow, require little care, have a famous fragrance, and come in variations of red, pink, white, and purple.  Even though blooms only last a couple of weeks, with a diversity of different plants from the various species you can have blooms over a 6-week period.

The two main requirements for lilac bushes to succeed are a well-drained soil and full sun.  They will tolerate some shade, but won’t be as dense nor bloom as well.  Once established, they will even tolerate dry soils and drought. Make sure when planting you allow plenty of room for the mature size of a lilac (maybe 8 to 15 feet tall and wide), otherwise you may need to “basal prune” all stems back near the ground, and then wait a couple years for new shoots to develop and get a few feet tall.

You should plant a lilac where you can appreciate their informal upright natural shape. Lilacs are often seen near building foundations, and are especially good near corners.  They make great specimens in lawns and borders, and planted in a line make a fine seasonal hedge.

If you like the look of neatly rounded shrubs, most lilacs won’t please you, although there are a few exceptions. The single purple Paliban Korean lilac (Syringa meyeri) which grows 4 to 5 feet tall and a bit wider, and the single violet ‘Miss Kim’ Lilac(S. patula). Both have a rounded habit, unlike other lilacs.

Once established, fertilize lilacs lightly once each year if at all.  In good loamy soils, or with some compost placed around plants, they may need no fertilizer.  If fertilizing, do so right after bloom.  Too early and flowers may abort with only foliage appearing. Too late and plants may not harden properly for fall.  Around the fourth of July is about as late as you should fertilize, or for that matter prune.

Types of lilacs

Most lilacs gardeners are familiar with the common lilacs (S. vulgaris) and their cultivars (cultivated varieties) that bloom in mid to late May in the northern U.S..  Some that bloom just a bit earlier are the hyacinthiflora hybrids, first bred by the famous Lemoine nursery in France in 1876.  Examples of these are the single purple ‘Pocahontas Lilac’, the single white ‘Mount Baker’, the single blue ‘Blanche Sweet‘, or the single magenta ‘Asessippi‘.

As you see, lilacs come in more colors than “lilac” and white.  Lilac specialists have grouped the over two dozen species and hundreds of cultivars into 7 flower colors: white, violet, blue, lilac, pink, magenta, and purple.  For each of these there are singles and doubles.  In addition there is the single yellow ‘Primrose’and the bicolor ‘Sensation’.  The latter arose as a mutant in a Dutch greenhouse (from the lavender ‘Hugo de Vries’ that was being forced to flower at Christmas) in 1938, and has purple petals each in white.

The other large group are the late lilacs, mainly the Preston hybrids originally bred by a Canadian breeder by that name.  These may not have the wonderful fragrance of the common lilacs, but bloom a week or 10 days later and tend to be larger in all respects– leaves, flowers, and wider plants.  A few of my Preston favorites are the deep pink ‘Miss Canada‘ and ‘Donald Wyman’, and the white ‘Agnes Smith’.

I often get asked what is my favorite lilac.  It is hard to answer as so many, in fact most including the common species, are beautiful.  The one that stands out for me and many though is ‘Krasavitsa Moskvy’, or as many know it Beauty of Moscow.  It was selected by a famous Russian breeder in 1947 from an offshoot of ‘Belle de Nancy’– one of the French Lemoine hybrids. The pink buds open into creamy white flowers tinged with pink, a silvery opal color.

How to prune a lilac

When it comes to pruning lilacs, experts have a couple of opinions. Some (such as myself) only prune branches as needed, eventually removing about a third of old branches each year.  This allows the plant energy to produce new branches.  Eventually most lilacs will get very tall, with most of the flowers appearing at the top.  This makes the blooms hard to see up close, but fine from home windows, the street, or at a distance.  Plus, with some pruning of lower branches you can appreciate the attractive stem architecture.

Others like to prune about a third of new growth off each year, back to sideshoots, not sheared like a hedge.  This keeps plants and their flowers lower, but sacrifices the natural shape and effect of the stems. If you need to prune lilac branches that are obstacles, or crossing and rubbing on each other, do so right after bloom.

Lilac pests and diseases

The main problem you may see with lilacs is the white powdery mildew disease on leaves.  This will be most common if if your site has late morning dew and little air circulation. Powdery Mildew is more of an aesthetic issue with lilacs and doesn’t cause enough harm to plants to warrant treating.  During very wet springs some branches may suddenly wilt, and their tips turn black. This is a blight which should only come once, and new buds should emerge from stems in a few weeks. Occasionally a lilac may get small rounded brown bumps, or scales, which can be treated by cutting off the infected branches.

This article originally appeared on Perrys Perennials.

About Dr. Leonard Perry

Dr. Leonard Perry is an Extension Professor at the University Of Vermont. He serves as an advisor and consultant to the greenhouse and nursery industry, including the Vermont Association Of Professional Horticulturists. His research focus is on herbaceous perennial production systems.
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31 Responses to Lilacs: Tips on planting and growing

  1. Carla says:

    I have 2 very old lilac bushes that are pretty wild looking. They were planted by the previous home owner in a spot that is not conducive to our enjoyment of them, and I would like to move them. What is the best way to move such large trees?

    • Todd Heft says:

      Carla:
      I know how it is. When I bought my current home, I went on a mission to move every shrub to a “better” position. And I killed more than half of them. Lilacs are especially fussy shrubs and if the new site you move them to is not absolutely perfect for them, they may be resentful and die. What do I mean by perfect? Loose, loamy soil which drains well, and at minimum, 6 hours of direct sunlight each day during spring, summer and fall. Direct sunlight means that the shrub is actually being hit by the light. Early day sun is preferable to late afternoon sun.

      You should also be aware that if the shrubs are very old and I’m assuming very tall, the root ball is going to be immense. It will extend a few feet beyond the shrub and will probably be more than 3 feet deep. And it will be very dense and heavy.

      So knowing all that, if you still want to move them, choose your spot very carefully, dig the root ball out carefully (don’t sever more root than is absolutely necessary) and use 2-3 people to move each one. When the lilacs are in their new home, add compost and peat moss on top of the soil around the shrub to feed it and condition the soil (but not in the hole and no mulch volcanos). To make the move easier, you can safely prune back up to 30% of the bush without hurting it – work on the obviously dead wood first and tangled and crossing branches. But don’t count on any blooms the year you move it, as it will take time to adjust to its new home.

      • Carla says:

        Thank you so much for this thorough explanation. With all of that in mind, I think that I will try to make them work where they are, and just prune them way back. Thanks again!

  2. Laurie Turton says:

    Is it necessary to remove old blooms every year ? Does this create room for future blooms?

    • Todd Heft says:

      Laurie: there’s no need to remove old Lilac blooms. In fact, the shrubs need little pruning, except to occasionally trim out dead wood from the interior.

  3. Trista says:

    I was just gifted a potted Bloomerang Lilac Bush and I am wanting to plant it in front of my house. Could I plant it now or should I wait until this fall? I live in the Midwest.

    • Todd Heft says:

      Trista: If you plant it now, you’ll have to baby it through the heat of summer, and who knows how bad it will get? If it’s in a container of sufficient size (plant will show no signs of stress like yellowing, dropping leaves), I would keep it in a protected area until mid-September or early October and plant it then. When you do, add lots of organic material like compost on top of the soil as a mulch around the roots. Water thoroughly and frequently until winter arrives.

  4. Kelly says:

    We purchased a new lilac bush and planted it 2 summers ago, it has direct sunlight and has grown each season however has yet to bloom? Any suggestions on why?!

    • Todd Heft says:

      Kelly: Does it receive direct sunlight all day (dawn to dusk)? Lilacs demand as much sun as possible

    • Alice smith says:

      My sister uses leftover pieces of Sheetrock around her lilac… Just break it up, lay it down around the stems. You could cover it with mulch to make it less obvious. Oh, and, it does work!

  5. Tina Swinford says:

    Todd,

    We moved into a new house that had a well established Lilac in full sun (8 yrs old). The blooming went great this spring then suddenly half of the branches broke and the bush is lopsided. Any suggestion how to fix? Should I cut it back alot this fall?

    • Todd Heft says:

      Tina: That’s unfortunate. It’s not an age problem, as 8 years isn’t very old for a lilac. I would have a couple of questions without seeing pictures: 1. Are all of the broken branches on one side or one area of the bush? 2. Is there standing water around the bush? 3. What kind of soil is it planted in? 4. Are you using any kind of fertilizers?

  6. Teresa says:

    Hi,

    Thanks for the great information. We have a lilac tree that was probably planted when it had a better chance at some sun. Now a huge willow tree and pine trees cut all but maybe some southern sun late in the day. I don’t want to move it because its creating a nice barrier between us and a cranky neighbor. It does have a couple dozen blooms on it each year but its probably close to 17 feet tall. My question is, is there anyway to propagate from clippings of this tree to plant in a sunnier spot if my yard? It’s a beautiful, hardy tree, obviously.

  7. Sue says:

    Hello, thank you for all of this great information. We moved to our home in northern VA 3 years ago. There are two lilac bushes – one in an odd location between us and our neighbor that has a wind tunnel effect so it’s growing sideways and sparsely blooms and another that is in the shade and has never bloomed. I would like to replant them to sunny, appropriate spots – any tips on digging up and transplanting? Time of year, soil prep in new spot, etc? Thanks much!

    • Todd Heft says:

      Sue: The best time to move the lilac is after its normal bloom time. As you’re in Virginia and the summer may be extremely warm, I would suggest waiting until after Labor Day. Lilacs are very particular about being moved, especially since it sounds like these have been very stressed, so you want to do it as seamlessly as possible. Have its new home dug and ready to go when you dig out the bush so it sends a minimum of time out of the soil. The lilac is obviously more than 3 years old, so the roots may have extended quite far down into the soil or quite far from the dripline of the shrub just beneath the surface. So when you dig the shrub out, the idea will be to dig as wide and deep a hole as possible to preserve as much of the root structure as you can. Be very careful about keeping the main root intact – the part that is just below the shrub. Placement: sun, sun, sun, dawn to dusk for best blooms. Soil: Lilacs don’t like soggy roots, so make sure the area you’re transplanting to drains well – it shouldn’t be a low-lying spot where rainfall tens to puddle – and the top of a slight incline protected from wind is best. Work in a lot of compost and peat moss into the new soil and side dress with the same after planting. Lilacs like soil on the acid side, so use peat moss around it each season. The lilac may not bloom the following year due to the transplant stress, but if the transplant was successful, you’ll see new buds in spring. Good luck!

  8. Pat says:

    I have 2 lilac bushed about 4 ft high they start out green and lush but the the leaves curl and are killed by small worm-like pests. I have sprayed them with SAFER INSECT KILLING SOAP but just cannot seem to get ahead of these pests. Any suggestions?

    • Todd Heft says:

      Hmm.. Tough for me to know what the pest is without pictures. However, what you describe is confusing, because that “worm-like” thing doesn’t fit with common lilac pests. It could be that your lilacs are sick and the insects are secondary – they’re arriving because the lilac is sick, they’re not actually making it sick.

      First thing I would do is get the soil in shape. Scratch the ground around the bush with a hand tiller being careful not to disturb the roots. Add lots of compost (like 3 inches) and peat moss. Then add a balanced organic fertilizer, like 5-5-5. Let it sit. Do the same thing in fall. This season is finished for the lilacs, but try and save the bush for next season. And stop spraying anything, because it’s not working. If you can make the bush strong enough to resist pests, no pests will bother it.

  9. Crystal Gravit says:

    I brought a house that had two lilac bushes. They don’t grow well and are in full sun all day. Half of the branches do not grow leaves or flower. They look very sparse and shabby. What can you recommend to help?

    • Todd Heft says:

      Crystal: There are a handful of reasons that come to mind. Firstly, when you say “full sun all day”, does that means dawn to dusk or some portion? Lilacs just love sun and get cranky without enough of it. If they do indeed have lots of sun, I would bet that you have some kind of soil problem, because it sounds like they aren’t getting what they need. Add composted manure for growth, bone meal for flowering, and finished compost for drainage. First scratch the surface around the bushes with a yard rake or hand tiller (gently loosen the soil-don’t dig), and then add to the surface around the bushes, out to the drip line. Be careful not to disturb the roots. Have any synthetic fertilizers or herbicides been used near the lilacs? How old are the bushes? (Tell me their height)

      • Crystal Gravit says:

        No fertilizers have been used since I have owned the house, almost 3 years and they are in full sun till dusk. They are around two feet tall because I pruned them last year to remove all the dead limbs due to lack of care. I will definitely amend the soil. Thank you for your help!

  10. Deb says:

    I live in the Northeast. I “found” a lilac growing between my maple trees and replanted it about 10 years ago. It doesn’t get full sun, but does get a lot of sun. Some years I’ve gotten a few blooms and other years none at all. Any suggestions for more blooms?

    • Todd Heft says:

      Deb: There are a few reasons why your lilac may not be blooming consistently. “A lot of sun” is a relative term. Lilacs need at minimum 5 hours of full sunlight each day, and preferably more. Early sunlight is best if a choice has to be made. Some also make the mistake of fertilizing lilacs, which is rarely necessary. A lot of nitrogen makes the plant grow tons of green stuff, but few blooms. Sometimes this can inadvertently occur due to lawn fertilization, another reason I discourage the use of chemicals on your lawn. Finally, if your lilac is ten years old, it’s probably pretty large – do you prune it? The hardiest blooms are produced on new wood, so you may want to prune out the old growth immediately after this years’ flowers have faded.

  11. LISA says:

    Can lilacs be raised and kept potted?

    • Todd Heft says:

      Lisa: Not unless you have an awfully big container or a dwarf variety. Standard lilacs usually grow 8-10 feet wide and tall, so I wouldn’t recommend it. However, last year at a local garden center I saw a lilac tree, which is created by grafting a lilac onto tree stock. It’s beautiful, because it’s only about 6 feet tall and has a sort of lilac globe at top. It puts the blooms at eye level, which makes for an amazing aromatic experience when you walk past it. The lilac tree was planted in a large container (24 inches tall, I believe), so in that case, yes. I didn’t find much info online, but there’s one here (not endorsing the grower, as I’ve never bought anything from them): http://www.thetreefarm.com/lilac-dwarf-korean-patio-tree

  12. sondra burgess says:

    We live in Alaska where these bushes bloom all over the place yet we bought two of them and after the first year when I think we had 2 blooms, they have never bloomed again. We have had them for 8-10 years. What can we do?

    • Todd Heft says:

      Sondra: My first questions are: have you planted the lilacs in a sunny spot; did you ever prune them; and did you buy the lilacs at a local nursery?

  13. Nancy Mace says:

    I have lilac bushes that are well over 100 years old but they have gotten too tall. How short can I cut them without shocking them or killing them?

  14. Brenda says:

    Will lilacs grow in Fort Worth Texas area

    • Todd Heft says:

      Brenda: Lilacs have been bred to grow in a wide variety of climates. Most are hardy only to zone 7, but I’ve also read of some hardy to zone 9. Best bet is to check with your local independent garden center for their opinion on what might be able to withstand the Texas heat.