Cut to thin, shape and maintain shrub's health


Common lilac (Syringa vulgaris and "French hybrid lilacs)

Honeysuckle (Lonicera species)

Dwarf lilac (Syringa pubescens patula)

Common lilac

It hadn't been pruned in a long time and had become a thicket, with some canes producing very little flower and dying back in midsummer. We removed some old canes to let light reach the vigorous younger suckers, and thinned those, too.

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Pruning a lilac is important for its health: Keep a lilac pruned so its main canes don't get thick enough to host lilac borer. (More and very useful info about that borer in What's Coming Up Ensemble Editions # 63 and # 114.)

When a lilac's grown unchecked for some years, it can be a real chore to cut out some of the old wood-- tough to work the saw between trunks crammed one next to another. So after you sort out an older lilac like this (below, left, before the cuts; below, right after), begin pruning it annually, a little bit each year rather than taking on this challenge again. Remove one old trunk each spring, sawing it out at ground level. Remove weak suckers. Thin the remaining suckers.

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Eventually, the thick trunks we left will need to come out, too. We removed the most gnarly that had the most evidence of borers.

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Here's before and after of a shrub that had become so crowded at its base and interior that it was producing foliage only at its extremities. It was unattractive, and harder to shear every year as the branches become thicker. On a cold day in late March we removed some old canes to allow new growth from the base and in the center.

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Could we have cut it all the way to the ground and started over? Yes. However, that would have eliminated this year's bloom and probably have resulted in a forest of suckers that would urgently need thinning. Leaving some of the old wood means there will be some bloom this year and suckering won't be so wild.

Next year -- or later this summer --- we'll remove the remaining old stems. Afterwards we'll put the shrub on an annual pruning schedule, to remove about 1/4 of all the trunks each spring. On that regimen, every cane will grow straight up (like the unbranched central canes above, right) to about four feet tall in year one, branch and bloom in its second and third years, and then be cut out in year four to make way for newer growth.


Dwarf lilac

Below: The dwarf lilac before pruning, then with the dead removed, then with the remainder thinned and shortened.

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(There's another problem here, beyond overgrowth that needed pruning...)