Lilac root systems are honestly pretty incredible. Over the years, these shrubs develop a dense, matted web of roots that’s almost impossible to break through. Plus, lilacs are pros at spreading out via tons of underground runners. If you’ve ever wondered what’s going on beneath the soil with your favorite spring bloomer, here’s the lowdown.
A Tough, Far-Reaching Root System
For the most part, lilac roots love to hang out just below the surface, creating a thick “root carpet” over time. This technically makes the lilac a shallow-rooted plant. But here’s the kicker: it’s actually a bit of a hybrid. Lilacs also send roots deep into the earth to anchor themselves and hunt for water and nutrients.
Because those roots love to wander, I always recommend installing a root barrier when you first plant them. This keeps the roots from invading parts of the garden where they aren’t welcome—which is a lifesaver if you want other plants to survive nearby! Just a heads-up: make sure you use a heavy-duty material. Lilac roots are strong enough to punch right through flimsy pond liners or roofing felt.
If you ever decide to remove a lilac completely, be prepared for a workout. Simply sawing off the trunk won’t do the trick. In fact, if you just cut the top off, the plant often panics and starts sending up hundreds of new suckers from the roots. To get rid of it for good, you have to dig out the entire root ball.
Keeping Those Root Suckers in Check
To keep your lilac from taking over the whole yard, you’ll want to remove root suckers regularly. The trick is to cut them off right at the base (where they meet the main root) rather than just snipping them at the soil surface. If you just trim the tops, the plant will actually be encouraged to send up even more shoots! Also, try not to prune the top of your lilac too aggressively or too often, as this can also trigger a “growth spurt” of suckers underground.
Now, suckers aren’t all bad—they’re actually the plant’s way of reproducing and ensuring its survival. But because they spread so much, spacing is key. When planting, give your lilac some breathing room—not just from other plants, but from fences and walls too. Usually, a three-foot gap is the minimum, but five feet is even better. Of course, if you’re planting a lilac hedge, you can tuck them in a bit closer together.
One common worry is whether these roots will damage your house or shed. Generally, you can breathe easy—lilac roots aren’t usually strong enough to crack a solid building foundation. However, old, unsealed garden walls are a different story. Lilacs can easily find their way into cracks and push through them. That’s why keeping that three-foot distance is so important, even at the ends of a hedge row.
