Lilacs are one of the most beloved spring-blooming shrubs, known for their incredibly fragrant and stunning flowers. However, many gardeners struggle to get their lilac bushes to bloom to their full potential. The good news is that with proper care and maintenance, you can have a lilac bush bursting with flowers each spring. In this comprehensive guide, we will explore the top techniques for encouraging more prolific lilac blooms.
Choose the Right Location
One of the most important factors in maximizing lilac blooms is site selection. Lilacs need full sun to flower optimally, requiring at least 6-8 hours of direct sunlight per day. Select a spot that receives sunlight throughout the day, especially in the mornings when sunlight is most intense. Morning sun helps dry dew from the leaves quickly, preventing fungal issues. Avoid planting lilacs in shade or areas with obstruction from trees, shrubs or structures. Dappled sun or partial shade will limit flowering.
Lilacs also thrive in areas with good air circulation. Allow ample spacing between lilacs and other plants to prevent overcrowding. Good airflow keeps lilac foliage dry, reducing disease problems. A site with a slope or elevation can further improve air movement around the shrub.
Provide Rich, Well-Drained Soil
Lilacs grow best in fertile, humus-rich soil with a neutral pH around 6.5-7.5. Before planting, loosen the soil and mix in several inches of aged compost or rotted manure. This will improve drainage and nourish plant roots. If your native soil is heavy clay, also incorporate organic matter like composted bark or peat moss.
The area should have good drainage to keep lilac roots from staying soggy. If you have heavy, compacted soil, consider amending it with peat moss or small gravel to improve aeration and water movement through the root zone. Proper soil preparation at planting time gives lilacs the ideal foundation for growth and blooming.
Allow Enough Space Between Plants
When installing multiple lilacs, be sure to allow ample room between each shrub. Most lilacs need a spacing of 8-15 feet depending on the expected mature width of the variety. Failure to provide enough space leads to overcrowding as plants enlarge.
Overcrowded lilac roots compete for water and nutrients, resulting in weaker plants and reduced blooms. Also make sure the area surrounding the lilac remains open, with no encroaching trees or shrubs blocking sunlight and air movement. Good spacing and air circulation keeps lilacs vigorous and floriferous.
Prune Every Year
To keep lilacs flowering freely prune every year. The flower buds form on old wood meaning stems from last year and previous seasons. Pruning stimulates the plant to produce an abundance of new wood where flower buds can develop.
In late winter or early spring when the shrub is still dormant, remove dead, diseased, and damaged stems Also thin inner branches to open up the center of the plant and allow better light penetration and air movement. Never shear lilacs into tight, formal shapes, as this ruins their free-flowering nature.
Time Pruning Properly
With lilacs, when you prune is as crucial as how you prune. The worst time to prune lilacs is fall. By fall, next year’s flower buds have already formed on the wood. Pruning in fall inadvertently removes many of the buds that would have bloomed come spring.
The optimal time is immediately after flowering finishes. In early summer, prune once the blossoms fade, deadheading spent blooms back to the first set of leaves. This directs energy into new growth instead of seed production. Mid-summer pruning can be done if essential, but avoid major cuts that reduce the shrub by more than 30%.
Avoid Excess Nitrogen
While lilacs need some nitrogen for healthy growth, excess amounts from fertilizer can be detrimental. Nitrogen encourages abundant foliage growth at the expense of flowers. Use a balanced fertilizer like 10-10-10, or an organic plant food applied in early spring and after flowering.
Avoid fertilizing nearby lawn areas, as the nitrogen can easily transfer through the soil to the lilac roots. If planted in lawns, keep grass fertilizer to a minimum around lilacs. Excess nitrogen leads to leggy, green growth with paltry blooms.
Water Moderately and Deeply
Lilacs bloom best with consistent soil moisture. Water thoroughly to saturate the root zone, then allow the soil to partially dry out before watering again. Use a soaker hose or drip irrigation to deeply irrigate the roots. Mulch around the base to conserve moisture and reduce watering frequency.
Avoid both severe drought and overwatering. Drought stress can cause flower bud drop and smaller blooms. Excess moisture leads to root rot and disease problems. Aim to provide around 1-1.5 inches of water per week for optimal growth and flowering.
Control Competing Plants
Lilacs resent competition for resources. Avoid planting them near water-hungry trees with aggressive root systems that can infiltrate and rob water and nutrients from the soil. Install a below-ground root barrier when planting lilacs near potential competitors.
Also keep the area around the lilac clear of weeds, which compete for moisture and nutrients. Surrounding lawn grass can be a problem, so maintain a mulch ring around the base of the lilac to reduce grass encroachment. Remove suckers promptly to prevent diversion of energy from blooms.
Disbud Flower Clusters
Sometimes lilac flower buds are clustered too densely on the stems, preventing proper flower formation. In early spring as buds swell, use hand pruners to thin congested stems, leaving 4-6 buds evenly spaced. This allows each flower room to develop into a large, rounded cluster.
Pinch or nip off extra buds using your fingers or pruners. Take care not to damage the nearby buds you are retaining. Allow them to remain sparse for maximum size and beauty. Disbudding avoids congested, undersized flower heads.
Support Tall Varieties
Some lilac varieties grow quite tall and benefit from staking, especially when in bloom. Install stout wooden stakes or trellises at planting time. In spring when growth resumes, loosely tie flexible bands to supports, leaving slack for bush expansion. Staking prevents damage from wind and rain.
Remove ties and stakes after flowering so branches can harden off properly before winter. Staking improves flower presentation and prevents storm damage during the bloom period. Support mature, top-heavy varieties like the French hybrids and larger tree lilacs.
Be Patient With Young Plants
Don’t expect newly planted lilac shrubs to burst with blooms right away. Most lilacs don’t reach peak flowering until at least 2-3 years old when the shrub is more mature and established. The first year, remove any blooms to direct energy into root development rather than flowers.
The second season, allow just a few blooms to form. Once the root system is robust and healthy, the lilac will begin flowering more fully year after year. Patience and attentive care in the first couple years ensures later success.
Rejuvenate Old, Overgrown Shrubs
Mature lilacs that have become overgrown and flower little can often be renewed through rejuvenation pruning. In early spring before new growth starts, simply cut back all the stems almost to the ground, leaving just a few inches. This stimulates vigorous new shoots from the roots.
Allow the new canes to grow the first season without cutting back. Then in second year, thin and shape the new growth. Normal bloom should resume in 1-2 years after rejuvenation pruning shocks the shrub into productive growth.
Follow these key tips for maximizing the flowering potential of your lilac bushes. With attentive care and regular pruning, you can enjoy springtime floral displays year after year from these popular landscape shrubs. A few simple cultural practices make all the difference in optimizing lilac bloom performance.
Let’s discuss some of the things we love — or that frustrate or intrigue us. There’s plenty to talk about once you sink a shovel into the dirt. It’s all part of gardening.
Many of your lilacs, I’m hearing, have been disappointingly shy of bloom. The tales are sad and the gardeners despondent about the lilacs that bloomed once — three years ago — and not again. Without their Rubenesque trusses of fragrant flowers, lilacs are just another big, green bush, no? Well, I’m here to help.
Let’s think first of the spot you’ve chosen. Lilacs need lots of sun to produce flowers, at least six hours of direct light daily. Perhaps, in your leafy suburban neighborhood, the trees have grown up around your lilac since it was planted, depriving it of sun. There’s precious little you can do, because a lilac wants what a lilac wants. You can: a) move the lilac; b) trim the trees; or c) plant another lilac in a more open location.
Maybe, if you’ve planted it recently, your lilac is just immature. Young plants need two or three seasons to establish a decent root system before they hit their flowering peak. Meanwhile, you can help it grow big and strong by keeping it watered, since these plants suffer in a drought. And that’s not a sprinkle, but a good, deep soak every week or so during the first season if rain doesn’t fall.
As with all shrubs, and especially newly planted ones, you should keep groundcovers, grass and weeds away from the base of the plant, since they rob it of water and nutrients. A nice blanket of mulch helps to retain moisture, but don’t pile it up in a volcano-like mound around the base, or you’ll be inviting mice to nibble the bark away on a cold, winter’s day when the mousy larder is bare.
Although lilacs are easy to grow and hard to kill, they wouldn’t mind a little fertilizer, especially in the early years. But don’t overdo it, especially with high nitrogen fertilizers, the nitrogen content being indicated by the first of three numbers describing the formula. Too much nitrogen — too much fertilizer in general — will get you big, healthy, deep-green leaves but not much flower power.
Nutrients of any kind, already in fertile soil or added by your hand, will go wasting if your soil is too acidic. Lilacs are lime-lovers, preferring soil with a pH reading of 6 to 7.5 on a scale where 7 is neutral (higher numbers are more alkaline, lower ones more acidic). The pH factor is like a gatekeeper, and if it is woefully wrong, it can prevent a plant from making use of soil nutrients, no matter how abundant.
If you live in a pine and oak woods, or on thin, sandy Pine Barrens soils common in the southern half of the state, if azaleas and rhododendrons thrive at your place, chances are your soil is on the acid side. The smartest way to check is to get your soil tested by your county office of the Rutgers Cooperative Extension Service. But here’s a general guide: If you need to lime your lawn, you’ll need to lime your lilacs.
The ideal lilac Brian Pettinger/Flickr
I inherited some truly ancient lilacs, since fallen prey to borers and rot and replaced outright. I did find that a serious pruning and a single dose of superphosophate (available at garden centers) kick-started them into blooming more prolifically. Follow the dosage recommendations on the package and water it in well. Phosphate is the element most associated with the production of fruit and flowers.
Speaking of pruning, prune you must, but do it in a timely fashion. If you have been trimming back your lilacs in fall or winter, there’s a simple reason why you have no flowers. You’ve cut them off, silly. Flower buds are formed in early fall, primarily on the current season’s growth. To stimulate the growth of new wood, which is inclined to flower, prune immediately after the lilacs have bloomed in spring — like now.
Lilacs are suckering bushes that will form an ever-widening thicket of branches, and it can be daunting to approach an overgrown 15-foot specimen armed only with a pair of loppers. Don’t be faint-hearted, since it’s hard to prune these puppies too much.
Preserve a reasonable number of strong, healthy limbs to serve as a framework, and then pare away crossing branches to open the center of the bush to light and air. Head back those tall limbs waving overhead by about a third to put flowers closer to your nose. Once you get an annual regimen going, you’ll want to get the saw and cut to the base one or two of the oldest, thickest branches to allow younger ones to develop.
Lilac suckers can become substantial new shrubs that can lead independent lives elsewhere, if you like. Sever the umbilical root attaching such offshoots to the mother plant, dig the daughter plant up with a substantial root ball and set it in somewhere else. If you don’t need another lilac, you can try to quell sucker production not by pruning them off at the soil line, but by digging down and tearing, rather than cutting, the sucker away.
As for deadheading spent flowers, experts are divided on whether this will boost the blossom quotient next season. This can be quite a chore on a big, sprawling bush; I just cut flowers for the house with abandon and leave it at that. Yearly pruning to promote new, flowering wood is really more important than clipping every faded flower truss away.
If you’ve done everything right and your lilac still won’t bloom, here’s a final trick I learned from Eric Welzel of Fox Hill Nursery in Maine, a specialty lilac grower: Scare it. No, no — not by leaping out from behind the shrubbery and shouting “Boo!” Make a scrape in the bark 2 or 3 inches long near the base of the trunk right after blooming season.
“Nothing fancy,” he says. “Just a boot scrape will do. This “shock method’ almost always works for me.”
The theory is that by stressing the plant, you frighten it into producing seeds so that it — or its progeny — will survive the threat. And what precedes seeds? Flowers, of course. Just don’t overdo it, since girdling the trunk (removing a ring of bark completely around the circumference) will almost certainly kill it.
And then you’ll have no flowers at all.
How to Prune Lilacs
FAQ
Why are my lilacs not blooming much?
Lilacs bloom best in full sunlight, or at least a half-day of sun. Anything less will mean fewer flowers developing. When they’re in a location that’s shaded all day, lilacs rarely bloom at all. Sometimes the shade creeps up over the years as nearby shade trees grow taller and fuller.
How do you rejuvenate a lilac bush to get more flowers?
You can rejuvenate an old lilac by cutting all stems to about 6”-8” from the ground. The best time to do this is in the early spring before the shrub leafs out. As you noted, you will sacrifice all the blooms on your plant. However you will be rewarded with a flush of new branches.
What can I feed lilacs to make them bloom?
Lilac plants do not need a lot of fertilizing or organic feeding. We recommend using a fertilizer that is low in nitrogen and high in phosphorus to promote flowering. Too much nitrogen in the soil can result in poor blooms. If the soil is low in fertility, you can mix cow manure into the soil to promote flowering.
How do you get lilacs to bloom?
The good news is that the following tips can help get lilacs to bloom and fill your garden with those sweet-smelling flowers. Lilacs need at least 6 hours of sunlight in order to produce blooms. If the plant doesn’t receive that much needed light, it won’t be able to produce those fragrant blooms.
Do lilacs bloom well?
Another issue with lilacs that do not bloom well is they are often incorrectly pruned in the spring. What you do in late winter and early spring can have a big impact on your lilac’s bloom cycle. Both with this year’s blooms, and for blooms next year as well. For starters, never prune your lilacs in the early spring before they come out.
What should a gardener do for lilacs?
One of the most important things you as a gardener can do for your lilacs is to prepare them for the next year. Not only does this help keep the plant healthy, it also promotes blooms for next year. Make sure to prune off any spent blooms or dead wood after the plant’s growing period.
How do you grow a lilac bush?
Steps: Mix the water and Epsom salt into a bucket. Pour this solution at the base of the lilac plant. Aside from that you also need to apply phosphorus-rich NPK fertilizer. Water the right amount and Remove the dead flowers from your lilacs. These should do the trick and make lots of blooms. Do Lilac Bushes Bloom Every Other Year?
How to care for lilac bushes in spring?
There are two big tasks to perform on your lilac bushes for spring care. The first is adding compost. And the second is applying a thick layer of mulch underneath its base. The compost will help to power your lilacs with just enough energy for great blooms. If too much fertilizer is given to lilacs it can actually cause them not to bloom.
Why are Lilacs not blooming?
The reason for the non-flowering of lilacs may be its transplantation since it will take several years for lilacs to fully bloom. It can take a few seasons for transplanted lilacs to deliver an impressive floral display. After being installed, your lilac will focus most of its energy on establishing a vigorous root system.