I trim all the Aster species (as well as many other perennials) sometime in June when they are about a foot high, maybe a little higher. I use hedge clippers and trim about 3-6 inches of growth tips off into a nice bushy mound.

Sometimes the deer trim some of them for me! They love Asters. They usually do a pretty good job if they only browse once, but they've hit the A puniceus a couple times this year and it looks pretty pathetic (this is Swamp Aster, collected seed in a local wetland and turns out it reseeds a lot).

Despite the trim my New England Aster Alma Potschke is still 3-4 feet high and a little lanky, but it definitely helps make them bushier and shorter, and less prone to flopping.

It sounds like you must have 'Purple Dome' Asters. Divide in the spring when growth starts. When you pinch back, do every stem, like the deer do. In our climate we need to extend the pinching to August, unless the deer make another pass. It is almost impossible to keep them short enough to keep them from flopping when in bloom. Al

Al

Are you sure you have 'Purple Dome'? That's a very short aster by nature. I don't think mine has ever grown over 15 inches tall. I've had it for years and I would never think of pinching it to control height because it doesn't grow tall enough where flopping is a problem.

Kevin

As per Aachen.

Below: Our front: 'Purple Dome' in front of 'Alma Pötschke'
(October 5, 2012).

I never reduce the heights.

Have also just switched to the (hollow?) metal stakes, with green plastic covering. They're excellent in several ways, but I find that one of them will only support several 'Alma Pötschke' stems. More stems and those stakes get permanently bent.

Yep, that looks like mine too.

{{gwi:272346}}

For some reason I lucked out with Alma this year. I didn't pinch, I didn't stake, it's about 4 feet tall and hasn't flopped a bit yet. Of course, rain is almost non-existent right now, so maybe that's the reason.

Kevin

Interesting about your Alma, Aachen.

We've had a lot of rain, periodically, though a lot of the Alma was staked early.

I've done more New England aster restaking so far this year than usual.

Perhaps bamboo stakes are needed in these circumstances, though they really don't add anything to a picture of an aster.

Hmm, I have what I thought was Purple Dome, and they are easily four feet high - after I cut them back earlier in the season. They are also quite upright at that height... I wonder if I have something different...?

Dee

Dee I have the tall purple ones too, in the back garden, and can't remember what cultivar they are either! I suppose I could rummage through the zip loc bag of old plant tags and might actually find it, but I'm too lazy, LOL.

Purple dome's are definitely short and dome like.

Thanks everyone for all your advice and pictures. I will try to trim my asters next year - I assume I can trim until they start forming buds. We don't have deer around here. Hopefully they will be more full next year like in your pictures!

The tall purple ones I have are 'Hella Lacey.' don't remember the species name.

This is really bugging me now. The only two asters I have ever bought are Purple Dome and September Ruby, and I know these purple ones aren't September Ruby. Gee, I wish I was more organized and kept better records.

The only thing I can think of is that perhaps I picked up what was labeled as Purple Dome at a swap, and the plant was mislabeled. I guess that is certainly possible.

Whatever this aster is, I really like it. Tall, upright, and beautiful purple color.

Dee

I collected seeds from a beautiful, low-growing purple aster. When the seeds grew, they must have reverted to a taller variety, because every plant I've ever grown from those seeds have been 4-5 feet tall. Though, I haven't had any trouble with flopping. I have trouble with the bottom portion of the plant turning brown and crispy. So, when they bloom, the top 1/3 is beautiful but the bottom looks like it should have gone on the compost pile long ago. I think I will plant annual Cosmos around them to help hide the unsightly lower portions.

Martha

Martha, mine are the same way. Beautiful on top, brown and crispy on the bottom, especially the clump in the hot sun. The ones in part shade are a bit more attractive - but I also noted this year they are not blooming as abundantly at the others. I hope it's just a delay thing and they will bloom as much as the others in time. Otherwise I may have to move them. Seems my few sunny & partly sunny spots are getting shadier by the year!

Dee

Sometimes N.E. asters are determined to be tall in spite of cutting back.

I have a seed-grown strain (Benary's composition mix from Chiltern's) that I cut back in early to mid summer by around half. Plants bloomed at nearly four feet tall anyway and I've had to stake them (according to the catalog they're supposed to mature at 2-4 feet tall). A. Potschke never was trimmed, has been flowering heavily at about 2 1/2 feet and probably should have been staked too (it's leaning, but still looks good).

I had help in trimming from the deer early on, but mine still got to 4+ feet, too.

Martha

I would get lace bug on my asters every year and they would get crispy dead lower leaves. This year they didn't get it . Probably will get it next year if it doesn't rain enough...