Get Ready to See Your Lilacs in a Whole New Light—Here’s What to Do This Spring

Very soon, your lilacs will burst with massive panicles of sweet-smelling flowers in white, purple, violet, pink, blue or even yellow. And your garden will also fill with butterflies and pollinators, attracted by their eye-catching “floral cones”, that form walls of blossoms. But what can you do to make sure that these gorgeous spring flowering shrubs give you their very best display?

Spring is not just the time to look forward to lilacs blooming; there are a few things you can do to help your Syringa shrubs explode with colorful and fragrant flowers; just follow me and you will find out.

1: Spring Is a Good Time to Check the Health of Your Lilacs!

I would actually say that early spring is an ideal time to make sure that your lilac shrubs are healthy and ready to bloom. Soon, they will grow so much foliage that you won’t even see their branches any more, so, the sooner you give them a good “check-up”, the better!

Thoroughly check all the branches now, and look for any sign of infections and diseases, especially fungal and bacterial. Winter being a cold and wet season, your lilacs may have caught some ailments.

If you find branches that are beyond saving, prune them off now; some may have died, or may be dying, some may be dry etc.

On the other hand, if you find molds and infections but you can save the branch, use neem oil. Actually, I suggest you give your lilacs a good “disinfectant bath” in spring anyway. It’s very simple.

• Fill a spray bottle or tank with water.
• Add 1 to 2 teaspoons of neem oil per liter of water.
• Squeeze in some liquid natural soap.
• Shake well and spray your lilac shrubs thoroughly.

This will cure any fungal and bacterial infections they may have, and prevent new ones. It will also keep pets at bay, neem oil is toxic to animals, fungi and bacteria, but totally safe for plants.

I suggest you repeat this operation every two weeks till the season gets drier.

2: Improve Drainage for Your Lilacs at the Beginning of Spring (or as Soon as You Can!)

If you haven’t done it yet, it’s really time to improve the soil’s drainage for your flowering shrubs. Winter and spring rains can be quite heavy, and lilacs, like most plants, don’t like to have pockets of stagnant water around their roots.

What’s more, winter may have depleted your soil’s drainage, so spring is a good time to scatter a 1-inch (2.5 cm) layer of coarse gardening sand all around your lilac shrubs (5.0 cm), or even more if the soil has compacted badly.

On the other hand, if your soil type is heavy clay, you should be using gypsum instead; coarse sand won’t be able to break it up.

Don’t dig it in! Just let it seep through naturally.

3: Help Your Lilacs Grow and Blossom with the Right Fertilizers!

The overwhelming floral display you will soon get from your lilac shrubs needs a lot of energy to put on, and this means nutrients, so… fertilizing, of course! But you need to give them the right “food” and at the right time, of course.

• In early spring, feed your lilacs with a balanced, slow-release fertilizer. At this stage, these shrubs need a wholesome growth prompt. I suggest a layer of compost (1 inch or 2.5 cm). A good quality organic granular fertilizer with NPK 10-10-10 or 12-12-12 (maximum 16-16-16) is a fair alternative.
• When you see the first buds, shift to a fast-release liquid fertilizer with NPK 10-20-10 or 5-10-5, which will boost flowers, but do not over-fertilize; I’d suggest you stick to half the dosage suggested.

Do not fertilize lilacs when they are in bloom! You can give them some compost afterwards, or, again, a balanced fertilizer to “catch their breath” after such a big floral effort.

There are some popular alternatives, like fish emulsion, compost tea (balanced) or a tablespoon of Epsom salt (to boost flowering when you see the buds) are also possible.

4: Watering Lilacs in Spring? A Matter of Flexibility!

I know, you’d expect me to tell you, “Give one gallon of water per shrub a week…” Well, to start with, I would be wrong, because a mature lilac needs 5 to 10 gallons (20 to 40 liters) a week, which is about 1 to 1.5 inches (2.5 to 4.0 cm). But there’s a problem…

Spring can be a wet season, so you’d risk overwatering your lilacs if you followed this rule with no exception. So, be flexible! Don’t irrigate these flowering shrubs if it has rained, if it’s in the weather forecast soon. What is more, check the soil; when the top 2 to 3  inches are dry (5.0 to 7.5 cm), they are thirsty!

Finally, deep-irrigate your lilacs! It is better to give them lots of water once a week than a bit very often. Why? This way it penetrates further into the soil, and it will encourage your shrubs to grow deeper roots.

5: Mulch Your Lilac Shrubs Abundantly in Spring

If you haven’t mulched your lilac shrubs, or replenished it already, it’s time to do it! Never leave the soil uncovered as a general rule.

You can use any type of mulch you like, some are more expensive, like wood bark, but more decorative; others are cheap (like straw), and they decay faster. Choose according to your needs, and if you don’t know how to select it, we can help you with our article on“which type of mulch to use where” here!

I suggest you mulch your Syringa after you have fertilized them and improved the soil’s drainage.

6: Careful with Pruning Lilacs in Spring!

Pruning lilacs in spring is a dangerous job! To give you those massive blooms, they start growing them soon after they have stopped flowering! So, you have to be careful.

In fact, there are two types of pruning for lilacs in (or just after) this season.

In late winter or early spring (at the very latest), you can simply “tidy up” your lilacs, for health reasons mainly:

• Focus on dead and very sick branches, which you can prune freely.
• You can also cut some very tall branches, which only blossom at the top, so your lilacs concentrate their energy on the other ones.
• You can also prune very overgrown branches, cutting them back to the size you want your shrubs to be, and this is just to maximize space in your garden.

In every case, prune about ½ inch (about 1.0 cm) before a healthy shoot and with sterile blades.

On the other hand, you need to keep your pruners ready, because you will have a big job to do at the end of the season. And we will see it next.

7: Pruning Lilacs After They Have Bloomed

This may happen in early summer or late spring, at the very end of the season. As soon as your lilacs stop flowering, it is time to prune them.

This is the main pruning of the year, but don’t delay because lilacs will start growing new buds within two weeks after they have blossomed (even if you can’t see it)!

So, here is how to do it:

• You will need loppers, a saw and pruning shears, for bigger and smaller branches; but always disinfect them before every shrub!
• Never prune off more than 1/3 of your lilac shrubs.
• Focus on old wood, and thin out overcrowded parts.
• Also, prune back all the branches to the size you want your shrub to be.
• Prune all dry, very sick and overlapping branches.
• This is also a better time to cut back those tall branches that only flower at the top.

Which leads me to the next point…

Expert lilac gardeners give what’s called “rejuvenating pruning” to lilacs every three years. This is because these shrubs do bloom on old wood, but after a while, you get long, thick and hard branches that do not flower at all.

So, cutting them back (really back to the ground or where they start!) rejuvenates your lilac shrubs and guarantees massive and dense blooms.

• Find the very old branches, you will recognize them because they have a rough surface, not smooth like younger ones.
• Cut them back totally, either to the ground or where they originate. You will need a sterile and sharp handsaw to do it; wear gloves for safety.
• Here you will find many of those tall branches that only flower at the top; cut them back too!

I will repeat, this pruning must be done as soon as the lilacs have stopped flowering, at no other time, so, late May to early June.

8: Deadhead Your Lilacs When and After They Flower

Never leave a single spent bloom on your lilacs! It will soon go to seed, and the shrub will divert lots of energy to it, diverting it from the other panicles of flowers. On top of that, they don’t look good, so…

Keep checking your lilacs for spent blooms and deadhead them, then, when their flowering season, remove all the panicles. You can use a little sharp blade, like a grafting knife, and cut the stem back to the first healthy set of leaves.

But now, time to think about propagating your lilacs, and spring is an excellent time to do it. At different times, and in different ways!

9: Propagate Your Lilacs in Early Spring by Root Suckers

Look around your lilac shrubs; if yours are adults, you will see small “babies”, little shrublets coming out of the ground. These are root suckers, shoots that come from the roots (of course) of the mother plant.

And they can grow at some distance from the mother shrub, unlike other plants like oleanders, pomegranates and olive trees, and early spring is a good timeto take advantage of them and propagate your lilacs!

It is actually the safest way to propagate your Syringa shrubs, and quite easy to boot. Here is how.

• Find a healthy sucker.
• Dig around it, about 6 inches (15 cm) from the base.
• Clean under the sucker, so you can see where it attaches to the root.
• There should be some small roots growing before the attachment.
• With a sharp spade,cut the sucker just above the main root it is attached to. Keep as many roots as you can.
• Transplant the sucker; it will soon become an independent young shrub!

Very easy!

10: Propagate Your Lilac Shrubs by Softwood Cuttings in Late Spring or Early Summer

As soon as your lilac has stopped flowering, so in late spring or early summer, you can propagate it by softwood cuttings. Don’t waste time, because this is when your shrub reverts to the vegetative phase, so when it grows leaves and roots.

Here is how to do it:

• Choose a healthy green stem, which has not flowered.
• With a sharp and sterile blade, cut the last 6 inches (15 cm).
• If the cut is not sharp, place the stem on a flat surface and refine it (you can reduce it to 4 inches, or 10 cm).
• Remove all the lower leaves, leaving only the top ones.
• Dip the bottom in a rooting agent; a simple, powerful, cheap and natural one is apple cider vinegar
• Prepare a pot with fertile, well drained and organically rich soil.
• Water it.
• Place a transparent plastic bag with holes over it, or use a ready-made propagation dome.
• Place it in bright but indirect, filtered light.

Then, keep it humid but not wet, check on it regularly, and when it starts growing new leaves, it means it has set roots and you can transplant it. It will take about a month, but then you’ll have more lilacs in your garden, for free!

The Two-Phase Spring Care for Your Lilac Shrubs for Lots of Blooms

As you can see, you need to distinguish your spring care in two main phases, before lilacs blossom (early spring) and after they have flowered (very late spring or early summer): this is the main secret to get massive blooms year after year. Follow these 10 tips, and your garden will be a sea of blossoms!