Pruning Lilacs on the Old Homestead - What I Learned...

Before Pruning

It is late winter in the Treasure Valley, and you live in a rural area in an older home. The poplars have aged out and there are several stumps in the yard. The silver maples bordering the pasture are taking over. The cottonwoods are huge and messy. You play pick up sticks after every storm. The sumac is long and leggy and the one and the only lilac has been ignored for a long time. It attacks you when you mow and is curling under the eaves. There is a plan to paint the house this summer, so a plan is required to minimize the lilac’s size, so I began my research!

The best time to prune a lilac is in the spring a month after it blooms. This gives the plant plenty of time to develop buds for the following year. If flowering is your main priority, this is a good time to prune.

Lilacs can also tolerate a “hard prune” also known as rejuvenation pruning when dormant, which is cutting all the old stems to within 6-12 inches from the ground. In the spring new stems will grow. The advantage to this is that it really does not require much skill. The disadvantage is that it could take up to 3 years to bloom again.  This is best for lilacs that are overgrown and no longer flowering.

Selective heading cuts are best for managing the size of the lilac. Heading cuts are made by pruning the terminal part of 30% of younger stems back to a bud. This will help maintain its natural shape.

An alternative to the “hard prune” is to thin the oldest lilac stems by 30% also known as renewal pruning, using the “Three-year Plan”, when dormant to open up the shrub and contain it in its allotted space. This will also increase light penetration and air circulation.

 This is what I chose. I planned to prune 30%, but not to top it using the following steps:

After Pruning

1.Remove dead and diseased limbs. Remove the debris. It already looks better.
2. Remove crossing branches.
3. Working from bottom, thin 30% of stems to open up the tree.

I laid a tarp on the ground for clippings and tried to evaluate how much I had removed. It has been suggested to me to take a picture before and after pruning to help determine when I had reached my 30% goal, remembering that 30% is an ‘eyeball’ estimate. Less is more as they say. There is always next year.

Leafed out and Bloomed!

How does the lilac look? Better, but not perfect. Leafing out will help it a lot. I checked it yesterday (03/26/26) and it is starting to leaf out, and I can see buds on the branches. If there is not hard freeze, it will bloom this season. Some sources advise fertilizing and mulching after pruning, but there was a substantial mulch of cottonwood leaves around it, and I can fertilize once water is available.

Conclusion: Reading about pruning and doing it are two different things. It didn’t turn out to be as daunting as I had feared.