Do Lilacs Prefer Full Sun, Partial Shade, or Full Shade?
If you've decided to add lilacs to your garden this season, it's a good idea to make sure you pick a proper location where they get the perfect amount of sun to meet their needs. In this article, certified master gardener Liz Jaros looks at the sun needs of the lilac, and if they prefer full sun, partial shade, or full shade.
Prized for their big personalities and sweet smelling blooms, lilac shrubs and trees bring undeniable joy to the landscape each spring. Hardy in parts of the world that have four distinct seasons, lilacs require a true dormant period in winter but also tolerate hot, sunny summers. They can be successfully grown in zones 3-7, with some varieties extending the genus into zone 8.
As for their light requirements, lilacs are sun lovers and need at least 6 hours of direct light per day in order to flower to their fullest potential. While their stems and foliage will usually grow just fine beneath a dappled tree canopy or in an area that gets less than 6 hours, their blooms will not be as robust.
So what does this all mean? Should you be strategically planting your lilacs in order to maximize their blooms? In this article, we look at the ideal sunlight conditions for lilacs and how you should plan for them in your garden. Let’s dig in!
The Short Answer
Lilacs definitely prefer full sun. In ideal situation, they should be planted in an area where they can get at least 6 hours of direct, unfiltered sunlight per day. If they get less than this, they will still grow, but they will not thrive. They will likely bloom less, and will not bring nearly as many of the sweet scented flowers that many gardeners plant them for.
The Long Answer: Defining Full Sun
A plant with a whole sunshine symbol or the words ‘full sun’ printed on its growing tag will need 6 hours of unfiltered sunlight per day in order to thrive. This is not a suggestion or a recommendation, it’s a requirement and should be taken seriously. Many to most plant failures can be traced back to a violation of this simple rule. If your plant tag says full sun, it needs full sun.
But the light does not have to be continuous! This is often a point of confusion among newbie gardeners. If you have an area that’s getting 3 hours of sun in the morning and 3 hours of sun in the afternoon, you can plant a lilac there. As long as the total number of hours is 6, you should be good to go.
Defining Partial Shade
An area that receives between 2 and 6 hours of sun per day qualifies as part shade. Occasionally you will see this middle category subdivided into part sun (4-6 hours) and part shade (2-4 hours). However, most growers use the term part shade to broadly describe plants that require somewhere between 2 and 6 hours of sun for proper growth.
You can probably grow most lilacs in part shade conditions, especially areas that lean toward being more sunny. However, you will probably not be gifted with the same floral explosion that you would if they were planted in full sun.
Defining Full Shade
While shade, by definition, means a complete absence of sun. In plant growing terms it’s used to describe locations that receive less than 2 hours of sun per day. A lilac planted in full shade will have little to no flowers at all. They will also have leggier branching habits, less robust foliage displays and high vulnerability to fungal conditions.
Avoid planting lilacs in full shade or if you think a location will have full shade when surrounding plants mature. If you can’t enjoy a bounty of beautiful blooms and you have to spend your time monitoring its health, planting a lilac in shade is way more trouble than it’s worth.
How Much Sun Do You Have?
If you don’t trust your basic powers of observation to determine the level of sun you have in a particular location, you can purchase a light meter from your local garden center. This will easily total the hours for you. But it’s also quite easy (and far more cost efficient) to measure the amount of sunlight yourself. Here are the steps:
Figuring Out Your Sunlight Amount
- Draw a simple diagram of your garden.
- Beginning at 7am, go outside and observe the sun.
- On your diagram, note the areas receiving direct sunlight at that time.
- Repeat every hour, recording hourly until sunset.
- This will help you document how many hours per day of sun a location gets.
- Keep in mind that sun angle and shadow length change throughout the season.
- Record light totals at three different points in the season; early, middle, and late.
Shade is Creeping in: What Now?
When a lilac that used to flower beautifully is no longer delivering the same bloom for the buck, take a minute to look up. This kind of bloom failure can often be traced to shady conditions. The shady conditions may have gradually moved in on a lilac’s once-sunny turf.
Maybe your lilac was planted alongside some other young plants and has been hogging the sunlight for years, but now the trees are starting to throw shade and the other shrubs are starting to rise up. Or maybe your neighbor put an addition on his house and it’s completely eclipsing your formerly sunny backyard.
While there’s nothing you can do about the shade from your neighbor’s new addition, consider having an arborist out to thin your mature tree canopies. They may also be able to remove some of the more imposing branches.
This might boost your lilac’s sun exposure a bit. And take a pruning saw to any neighboring shrubs that are overgrown or blocking the light. Fending off excessive growth from the other materials in your yard might help you buy back an hour or two of sun each day. And that can make a big difference to a lilac.
What if I Don’t Care About Flowers?
Let’s face it, most lilacs flower for 2 to 3 weeks tops and fade to green by late spring. If you take a vacation or have a busy stretch at work, you might even miss the show entirely. So is it the end of the world if your lilac doesn’t get enough sun and stops blooming? Of course not.
There are a few reasons why someone would still want to grow lilacs, even if they’re not going to bloom. Perhaps you’re looking for a fast growing shrub to create a subtle living fence on one of your property borders and are drawn to the wild, rambling nature of the common lilac.
Maybe you’ve happened upon a whole bunch of nicely-priced, small-leaf varieties at an end of season sale and want to use them as a formal hedge.
As long as your light conditions are closer to full sun than to full shade and you understand they will be leggier and mostly flower-less, you can plant lilacs in a less than ideal location.
Tree species are typically expensive and not recommended at all for shade. However, you might have better luck with something from the Common or Littleleaf lilac categories. Here’s a quick look at each of those species and a few cultivars you might want to try:
Common or French (Syringa vulgaris)
This is the lilac species that typically comes to mind for all of us. A fast-growing shrub with a wild habit that can reach heights and widths of 20 feet if left unchecked. Common lilacs typically feature smooth, heart shaped leaves and a loose, open structure.
‘Beauty of Moscow,’ ‘Miss Canada,’ ‘President Lincoln,’ and ‘Lilac Sunday’ all have a very traditional lilac shape and growth habit.
Littleleaf (Syringa pubescens)
Growing 5-7 feet tall and 8-14 feet wide, littleleaf lilacs feature tight branching, narrow leaves, and a more compact habit. They take shearing well and are commonly used as low hedges.
‘Manchurian,’ ‘Superba,’ and ‘Miss Kim’ can all be pruned into a formal shape, especially if you’re not worried about enjoying their flowers.
Lilacs require at least 6 hours of direct sun in order to grow properly and flower prolifically. That’s the bottom line on the genus and there’s no way around it. If you want to enjoy their blooms and encourage a healthy branch and leaf structure, you must guarantee these conditions are met.
Remember that these 6 hours do not need to be continuous. If a site gets 3 hours in the morning and 3 hours in the afternoon, that’s just fine, as long the sunlight isn’t filtered or dappled. While a part-shade location will not likely kill your lilac, it will also decrease your odds of growing a show-stopping, cottage charmer with sweet-smelling panicles of pastel joy. And that would really be a shame.