In temperate climates, where winters are cold and summers are warm, lilacs rule the landscape in spring. In both rural and urban areas, large, sweet-smelling panicles pop out of what look like normal shrubs and trees to pack a strong pastel punch. But only for a couple of weeks.
Lilac season is short and fleeting, and that’s definitely part of its allure. Even though they only last a short time, lilacs are still one of the most popular and easy to spot plants in hardiness zones 3 through 7. Even though the growing season is short, any gardener who has taken care of these pretty cottage plants will tell you it was well worth the work.
Here are 14 things you can do to make sure your lilacs have lots of beautiful blooms that last all season.
With 25+ species and thousands of cultivars, lilacs range in height from 3-foot ornamental shrubs to 30-foot trees. Lilacs come in many shapes and sizes, and their flowers can be white, violet, blue, lilac, pink, magenta, or purple. They bloom from early spring to early summer.
If you know the exact species and cultivar of your lilac, you’ll have a good idea of when it will bloom. Take some time to watch how the lilac acts if you’re not sure what kind it is. This should help you narrow down your choices a lot. After learning about its habits and flowering schedule, you can make a good plan for taking care of it.
Lilacs are treasured for their fragrant, colorful blooms that signal the start of spring. But sometimes these classic shrubs fail to flower abundantly. By providing the right growing conditions and care, you can encourage your lilac bushes to bloom more prolifically.
Follow this 12-step guide to get the maximum floral display from your lilacs year after year
1. Choose a Sunny Site
Lilacs need full sun to bloom well. They require a minimum of 6 hours of direct sunlight per day. Morning sun is especially important.
Plant lilacs in the sunniest part of your yard Avoid spots that get shade for large portions of the day. Dappled sun or partial shade can also limit flowering
2. Plant in Well-Drained, Fertile Soil
Lilacs thrive in rich, humus-rich, evenly moist soil The ideal soil pH range is 65 to 7.5.
Before planting, work in several inches of aged compost or other organic matter to improve drainage and fertility. Avoid soggy, clay soil.
If your soil is poor, amend it with compost or well-rotted manure when planting. Mulch lilac beds yearly with 2-3 inches of organic matter.
3. Space Lilacs Properly
Don’t plant lilacs too close together. Overcrowding leads to competition for light and nutrients, resulting in fewer blooms.
Refer to the expected mature size for the variety and allow ample room to grow. Space most lilacs 8-15 feet apart depending on their expected width.
4. Prune Every Year
Annual pruning is key to maximizing lilac blooms. The buds that produce flowers form on old wood.
In late winter or early spring when plants are dormant, remove dead and damaged branches. Also prune to shape and open up the center of the shrub.
Never shear lilacs into tight balls or formal shapes. Thinning cuts that remove entire branches to the ground are best.
5. Prune at the Right Time
When you prune is just as important as how you prune. Lilac flower buds form in the summer and fall for the following spring.
Prune soon after flowering since flower buds for next year haven’t formed yet. Deadheading faded blooms helps direct energy into new growth.
Don’t prune after mid-summer, as doing so will remove next year’s flower buds.
6. Avoid Too Much Nitrogen
Excess nitrogen fertilizer leads to lush green foliage but few flowers on lilacs and other spring bloomers.
Use a balanced fertilizer like 10-10-10 or an organic plant food. Apply in early spring when growth resumes and again after flowering.
If planted in lawn areas, keep fertilizer applications on grass to a minimum near lilacs.
7. Provide Even Moisture
Lilacs bloom best when their soil moisture needs are met evenly throughout the year.
Water lilac beds during dry spells so plants receive 1-1.5 inches of rain or irrigation weekly. Avoid both severe drought and waterlogging.
Mulch around plants to conserve soil moisture and reduce watering needs.
8. Limit Root Competition
Lilacs resent competition from tree roots or aggressive groundcovers. Don’t plant them near large trees.
Install underground barriers when planting lilacs near potential root invaders. Keep the area around lilacs clear of weeds.
If growth seems stunted, use a sharp spade to cut outward from the trunk to sever encroaching roots.
9. Disbud Overcrowded Clusters
Too many blooms crowded on a single stem prevents proper flower formation.
In spring when flower buds swell, use pruners to remove extra buds, leaving 4-6 buds per stem. Space evenly for best results.
Disbudding allows remaining buds to grow into large, fragrant flower clusters.
10. Stake Tall Varieties
Some lilac varieties grow quite tall. Stake plants over 5 feet high to protect against wind damage.
Set sturdy stakes at planting time. In spring, loosely tie flexible bands to stakes, leaving slack for bush growth.
Remove ties and stakes after flowering to allow proper hardening off before winter.
11. Wait 2-3 Years for Blooms
Don’t expect abundant flowers the first couple seasons after planting a new lilac shrub.
Lilacs don’t bloom heavily until they are 2-5 years old and well established. Have patience for the first few years.
The first spring, remove any blooms to direct energy into root growth. Allow just a few blooms the second year.
12. Consider Rejuvenation Pruning
If an overgrown, neglected lilac fails to bloom, rejuvenation pruning may help.
In spring after flowering, cut all stems down to 12-24 inches above ground level. This stimulates new, vigorous growth.
Continue pruning annually to shape regrowth. Blooming should resume within 1-2 years.
Follow these tips to ensure your lilac bushes receive the growing conditions, care and pruning they need to produce abundant, fragrant spring blooms. With proper attention, you can enjoy waves of blossoms year after year.
Give Them Plenty of Space
When planting lilacs, consider the distance between plants, as lilacs require good air circulation and plenty of sunlight.
Lilacs have very large, aggressive root systems. You can expect them to be as wide as the plant’s foliage or canopy. The area where they’re planted needs to be able to accommodate their size at maturity. When lilac roots are crowded, flowering will be reduced. So, it’s important to consider this when you’re deciding where to plant.
Lilacs also need good air flow to get enough sun and stay healthy, so you can’t plant them too close to each other (or anything else).
This can be one of the hardest rules to follow, especially when you’re working young, small plants. Do it anyway. You will reap the rewards with many long seasons of full-throated blooms.
Lilacs are strong feeders and do not typically need more than an early spring shot of fertilizer. Some horticulture professionals claim that lilacs need no supplemental fertilizer at all.
It’s really a judgment call. But if you feel like they need a boost, look for granules, spikes, or a slow release formula. These fertilizers will deliver nutrients gradually each time you water.
As too much nitrogen will make them leggy and leafy, rather than full and flowery, try a fertilizer ratio of 5-10-10, since you’ll want less nitrogen and more phosphorus and potassium (which encourage blooms).
Feed lilacs annually in early spring. Repeat bloomers (Bloomerangs) can get another dose later in the season. Follow your product instructions for quantities and application.
Keep them from getting too much nitrogen if they are planted in or near treated and fertilized grass. If you don’t, the blooms will suffer.
Water Enough, But Not Too Much
Lilacs are recommended to be watered deeply and slowly once a week.
Lilacs prefer well-drained soil and do not flower well if their feet are wet. Make sure your lilac isn’t planted in a low spot, next to a plant that needs a lot of water, or near a downspout.
Lilacs need regular, even watering during their first year, but after that, they usually don’t need extra watering. In the spring, soak them deeply and slowly once a week. In the summer, do it twice a week. As they do not like wet feet, make sure drainage is good and soil never puddles.
With that said, in times of severe drought, they may need a little extra attention. If leaves are droopy and the weather’s been hot, hit them with the hose now and then. They will thank you during peak season with beautiful blooms.
Make sure the soil is well-drained and does not retain standing water.
If the soil around your lilac stems doesn’t drain quickly and evenly after you water it, you might want to check it. If it is sticky and clay-based, work a little peat into the area, possibly even a little sand.
Strive to create a bed that drains evenly and does not hold standing water. If, on the other hand, the soil around your stems looks dry or is too easy to wash away, add some organic matter to make it more stable.
You may also want to test the soil to make sure your lilacs have the best conditions for growth. Lilacs prefer neutral to slightly alkaline soil. Shoot for a level somewhere between 6. 5 and 7. If pH is too low, add a little lime to increase acidity. If it’s too high, work some sulfate or bone meal into the dirt.
To make lilacs produce more flowers, be sure to cut off faded buds.
When flower heads start to die, it means that seeds are being made, so the flower’s growing system will shift its attention from making showy blooms to taking care of its roots and leaves.
We trick a healthy plant into thinking it should send up more flowers when we cut off flowers that are dying or have already faded.
Since lilacs bloom on old wood and make buds for next year as soon as this season’s flowers have faded, cutting off the spent flowers will encourage the plant to put its energy into making lots of beautiful buds instead of boring old roots and leaves.
Lilacs that bloom more than once, like ‘Josee’ and ‘Bloomerang,’ will have a stronger flower show during later blooms throughout the season if you remove the spent flowers.
To deadhead properly, use a small bypass pruner or scissors to remove spent blooms with a sharp cut just above the first set of leaves you encounter as you slide your fingers down their stems.
It is recommended to remove lilac suckers using a lopper.
If you see some random branches with leaves rising from the dirt around your lilac’s trunks, those are called suckers and should be removed. Growing directly from your plant’s roots, suckers do not flower or form side branches and they will drain energy away from the plant’s canopy or upper body.
Cut off suckers with a lopper right where they come out from the root. You may need to dig a little to get to the base of the sucker. Performing this routine maintenance task will redirect nutrients and energy toward creating beautiful flowers.
Lilac stems that are more than a year old should be cut back so that sunlight can reach the plant’s inner leaves.
Considered routine maintenance in most lilac shrubs, ‘renewal pruning’ involves cutting out roughly ⅓ of existing stems at the base. Begin with the oldest and tallest stems as well as those that are dead, crossing, or broken. Look for the thickest, woodiest stems to determine the oldest. They will usually be gray and have significantly fewer branches and leaves than newer growth.
This method, which is sometimes called “thinning,” will open up the middle of your lilac. This will let more sunlight reach the inner leaves, more water reach the roots, and better air flow. It’s a good technique for managing fungal disease, increasing bloom production, and keeping shrubs at their optimal size.
Another way to resume lilac bloom is to rejuvenate pruning.
You can cut down your lilac plant and start over if it is getting too big, leggy, or has stopped blooming. This process, which is called a “rejuvenating prune,” should be done when the plant is dormant, so it is not stressed by the work. It is an exception to the ‘prune immediately after blooming’ lilac rule.
Keep in mind, however, that your lilac will not be blooming again for a few years. This is a long-game strategy for restoring your lilac to its original glory and it requires patience. Here’s how it’s done:
- Start in winter or early spring.
- Use a pruning saw to cut evenly through their stems.
- Cut at a height of 6-8 inches above ground.
- Several new shoots will grow from the plant’s roots as a result.
- Next year, in the winter or early spring, pick the shoots that look the healthiest to keep.
- Prune off all others at the base.
- Cut back the last few shoots until they are just above a leaf or bud.
- This will encourage side branching.
- You can do regular maintenance pruning again the next year until it fills out.
- This should help maximize your blooms.
4 Expert Tips for Spectacular Lilac Blooms
FAQ
How do I encourage lilac to bloom?
What can I feed lilacs to make them bloom?
How do you rejuvenate a lilac bush to get more flowers?
How do you keep lilacs blooming all summer?
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?
Here are some tips to make sure yours bloom: Usually, insufficient sunlight is the problem. A minimum of six hours of sun is needed each day. Too much nitrogen can be a problem. Often lilacs are planted in the lawn and fertilizers used to green up lawns are high in nitrogen. For the lilac, this causes beautiful green foliage but little bloom.
How do you keep lilacs blooming?
In addition to proper pruning, fertilizing and deadheading of old blooms, there are a couple of additional factors that can play a role in helping your lilacs to bloom. Keeping the area underneath your bush free of weeds will help to conserve energy for the plant. Weeds take nutrients from the soil as they grow, and a lot of them.
Why are my Lilacs not blooming?
Even more than fertilizing, one of the biggest reasons that lilacs fail to bloom is improper pruning. Not as in how you prune your lilac bush back, more more importantly, when you do. If you want your lilac bush to bloom, there is only one time of the season you can prune. And that time? Right after they finish blooming!