How can I revive an old lilac bush that is over grown?

Most people trim their lilac bush after it has bloomed (we do). Then it has time to grow and will bloom on the untrimmed part next year. If you need to trim your lilac bush (since you don't know when it blooms) I would do it in late spring. I do not think lilac blushes bloom for up the three years after they are first planted. I would check with the local extension office or google lilac bushes to see what their habits are and where and when they should bloom.

Hello Debra; I would trim it back. However, I would consult with my local nursery, and I would ask them when is the best time to do this??

I usually pretty much only trim things in the spring.

I hope that this helps you!! Take Care!

Lila's only bloom on new growth. I would cut it back this year and fertilize it. It may not bloom next year but should grow stronger. I would expect blooms the following year one the new growth.

your question was cut off, but I assume it needs pruning to get the deadwood out and also trim away the branches that do not boom under the the canopy and you will have better blooms. it will also look more attractive when not blooming. when blooming, if you cut branches for floral displays cut them with an eye to shaping the bush nicely as well.

Here’s a rundown of the most common reasons a lilac might not bloom:

Shade: Excess shade is the most likely culprit when lilacs fail to bloom well. Lilacs bloom best in full sunlight, or at least a half-day of sun. Anything less will mean fewer flowers developing. When they’re in a location that’s shaded all day, lilacs rarely bloom at all. Sometimes the shade creeps up over the years as nearby shade trees grow taller and fuller. In many cases, the lilacs may have been planted in a poor location to begin with.

Pruning: If you prune lilacs back drastically, it may take a number of years before they begin to bloom again. They should produce flowers eventually, but it could take three or four years – maybe even longer. If you prune only lightly, but wait until mid to late summer to do it, you may not see many flowers the following year. That’s because the flower buds for the following year are set shortly after the plant is through blooming. So if you do plan to prune, be sure to do it right after the flowers fade in spring. At the very least, you may wish to remove the brown flower/seed clusters which are unsightly.

Nutrients: Lilacs are not heavy feeders; they don’t need fertilizer to make them bloom. Often, in an attempt to help young plants become established, people will fertilize them several times each spring and summer. Plus, there’s usually some lawn nearby, which is also fertilized. This abundance of nutrients, especially nitrogen, encourages the lilac to make a lot of leafy, vegetative growth – which may come at the expense of flower bud development. If this appears to be the case, and the plant receives plenty of sunlight and hasn’t been pruned too heavily or at the wrong time, simply stop the fertilizing. Eventually, it should begin to bloom well.

Moisture: Lilacs grow best in well-drained soil. While wet, poorly-drained soil isn’t directly associated with lack of blooms, it is associated with plants that develop root rots or generally fail to thrive. If you have a young lilac in a low lying moist location, transplant it to a more favorable site if at all possible.

Hi Debra, I hope the article in the link below helps you rejuvenate your "old...overgrown" lilac bush to bloom again. Good Luck :) Thanks for coming to Hometalk for help/

https://www.thespruce.com/pruning-lilacs-how-and-when-to-prune-lilacs-1403004

https://hortnews.extension.iastate.edu/1993/2-10-1993/lilac.html

Is your lilac healthy and merely overgrown, or not doing well? If it si not doing well, consider that lilacs like 'sweet' soil--try fertilizing with lime, lots of it. Are plants like tomatoes and rosebushes and rhododendrons thriving in the same area? If so, your soil is acidic, and it may be impossible to grow the lilac in that environment. Give it away on Craigslist.

Try pruning it, sometimes getting those old, dead branches will help them start blooming again

Try cutting it way back in the spring and hope for the best..

You can renovate it in stages, cutting out about one-third of the oldest branches at the base each year. That way, you don't have to look at a completely cut-back shrub that looks like a plucked chicken.