Lilacs should be pruned after they're done blooming and then trimmed down to eliminate one third of the plant. Prune lilacs with tips from a sustainable gardener in this free video on gardening.
Hi this is Yolanda Vanveen from vanveenbulbs.com and next we are going to learn about when is the best time to prune my lilac? When should I prune my lilac? It's a pretty easy philosophy. The best time to prune your lilac is when it is done blooming so as soon as the blooms have faded off and you know where they're going to bloom next year you just cut off all the dead blooms and trim it back and the key to trimming a lilac is only cut one third of it. If you have a really old lilac that is really out of control that has been there for years and years don't go in and just hack it down to the ground, gradually hack it back. So one third of it, hack it back the first year, one third of it the second year, one third the third year and eventually you'll have a gorgeous lilac plant again. So periodically I do trim or I prune my lilacs and the trick is as soon as it is done blooming because they set buds for next year but even in the fall once they are done blooming and the foliage has been there for a while just to trim it up again you can trim them in the Fall or the middle of the Winter and in the Spring as well and the plant will survive. So saying that in the Spring this bloomed beautifully and I cut all the dead flowers out and now we are into the Fall and for next year I want to give it some growth, I want to give it room to grow, I want to keep this very round and I want it to look really good in my yard. I don't want it just a tall lanky lilac so I'm going to really hack it back in the Fall so that it really grows well next Spring. So when I'm trimming it back I want to make sure and not trim too far down. I want to trim where a branch will hit the stem and at an angle. The trick is to do it at an angle so that the water just runs off of it, it is not sitting at the end. Some people take the time with lilacs and roses and they actually will put a little bit of Elmer's glue or some kind of sealant to help the plant but I don't even bother to do that because I have found that they survive no matter what I do to them, they survive. So I just want to really hack it back so that next year it will be more of a round circle and not this tall lanky bush and the big thing too is to make sure that you have lots of air coming through it because you don't want to have room if it is just a mass of leaves sometimes they'll get mold in the middle of it and they'll get really wet so if you make more air you'll get better flowers. So a lot of times as soon as they are done blooming I will cut out and trim out all the dead flowers but in the fall I really hack them back and that way they can really grow for the next year.