Lilac Bush Not Blooming Like It Used To

[sweettoothlady]

Hi, I'm new to the board.

I have a Lilac bush that was transplanted about 5 or 6 years ago. It was in a shady area, and I moved it into a nice sunny spot in the yard. The last few years I was able to enjoy nice flowers. This year, I only had one lilac on the whole bush. The bush is not very big. It's only about 4 feet high and a little over 2 feet in diameter at the top. In addition, the bush does not seem to get any larger.

Up until last year, I used wood mulch around the base of the bush. I changed it to lava rock last year. Would the lava rock be putting off too much acid? I noticed in some other messages about the possibility of too much acid in the soil.

I also have used Miracle Grow to fertilize in the past, but that is all. I also notice this year that there is a large ant colony in the ground around the bottom of the bush. Would this affect the bush at all? They are the black ants.

Any help would be appreciated.

[The Helpful Gardener]

The lava rock isn't affecting the shrub by chemistry, but it's not the mulch that wood is. You were getting better moisture retention and adding organic content (humic acids) to the soil before. I've said it before elsewhere but it bears repeating; if you aren't replacing the mulch every year (I.e. wood, compost, cocoa, etc.), you aren't doing anything. Your labor saving device is not a plant saving device by any means.

That said, what kind of lilac is it? Korean types mature at the height you are talking about. How are you pruning it? Fertilizing it?

Scott

[sweettoothlady]

Thank you for your quick response with your suggestions. I am going to put in mulch again, and take the lava rock out of my garden area.

I have been pruning it. I've also been giving it Miracle Grow, but probably not as often as I should. Hope this helps, as it is a pretty little bush, but not very leafy or tall, plus I just had one Lilac on it this year.

[Newt]

Ho Sweettoothlady,

You really need to stop fertilizing it. Too much nitrogen will cause lilac not to bloom. Adding a cup of lime to the soil when you put down the mulch would be helpful too. Lilacs tend to prefer a more alkaline soil. Take a look at these sites for some helpful info.

Guide to How to Prune Lilacs by HelpfulGardener.com

Newt

Btw, don't hesitate to write in again if this isn't helping.

Newt

[The Helpful Gardener]

Yep, water soluable nitrogen strikes again.

I like Newt's take on your problem, although the fertilizing could be done without the nitrogen (use potash and super phosphate at recommended levels). A nice organic mulch (I like compost best) will slow fertilize for a long time and attract natural benefactors like worms and mycorrhizal fungii.

As for the lime, I would use pelleted gypsum, as one or two heavy rains can wash the lime out; think of the pelleted gypsum as slow release lime...

Scott

[petunialover]

I have three lilacs in the vacant yard next door, I claim one of them (well we do mow the area every week!) It is close to my front yard, I trimmed it like crazy this year, RIGHT AFTER IT BEGAN BLOOMING I was told they bloom best if pruned before fall. I can't reach all the dead heads on the top but I know I should prune those... it has lava rock mulch and is still putting out suckers like crazy, I wish I didn't have to work so hard to keep it nice. The other two bushes are nearly house sized, way outta control! but not my problem, its just less to mow. our soil is acidic...

PL

[Newt]

Hi Petunia Lover,
Hope you took those flowers and put them in a vase so you could enjoy them. Actually, the best time to prune them is within two weeks after bloom. They begin to set their blooms very quickly after bloom and bloom on old wood. You could dig up some of the suckers and adopt them. They can take 5 to 7 years before they bloom depending on how small they are.

Newt

[The Helpful Gardener]

Petunia lover, I can tell from what you wrote you aren't pruning those lilacs correctly; you should be pruning at the base of the plant, so reaching should NOT be a problem.

Go to the lilac pruning section of the Helpful Gardener site for how-to's on pruning lilacs...

Scott