It shouldn't effect them at all, especially if they had already started turning brown. If they were cut in the middle of summer they might come back smaller next year.

I know some people who cut them very early in the growing season to keep them to a reasonable height. They should be fine. April

How wonderful! Thank you both. I thought they were like trees, so I didn't realize people ever cut them back at all. Thanks for explaining. :)

Tenderheart, eupatoriums are herbaceous perennials - they die to the ground at the end of each growing season. As with nearly all herbaceous perennials, they can be cut back to the ground as soon as the foliage fades with cold weather and frost OR one can leave them standing through winter and do the cutting back with spring clean up. With proper siting and reasonable care, all will grow back to their mideason sizes each year.

Pretty much anything that is not evergreen (retains a foliar presence all year) or has woody stems can be cut back hard in winter or at early spring clean up.

Pam, thank you for explaining. This is helpful. :)

It's a good idea to leave the seedheads (the part your mom thought was ugly) on during the iwnter. Birds will eat those seeds through the winter. I clean up my perennials in spring when the new growth starts.

I religiously deadhead this plant. The year I did not, I had several thousand seedlings to weed out.

Apcohrs,

I don't dead-head mine at all...after 3 years, I've only found 1 seedling..but maybe I'm just lucky, LOL! April

I don't know about Joe Pye, but my Eupatoriums don't usually die back during the winter. They DO drop their leaves, but in my zone, they're pretty much able to get their leaves back all over if not pruned back. Mine are woody perennials, not herbaceous.

for some reason i feel i must post something on this thread but everyone has already answered the question so i dont really have anything more to add ... specific to the question.

i was curious about the woody Eupatoriums, as i really wasnt familiar with those. So i did a little research and found out that the majority of north american Eupatoriums are perennial herbs, except those from tropical, warmer climates. The warm climate eupatoriums tend to be shrubby or tree like. which explains why the poster from Texas has experience with the woody ones, while the rest of us cold weather posters are familiar with the herbacious ones. i learned something new today :P

although joe pye is known to be overly self seeding and bordering on weedy, i have not had that experience in my plots. i think in certain soil conditions joe pye can take over. but is easily controlled by clipping the flowers before they go to seed.

Tenderheart,

You can keep the plants shorter by pruning the tips of the branches in early summer (whenever that is in TX I don't know). They will bloom slightly later, but will not be so tall and gangly. Just go for it! I was initially shy about trimming a beautiful growing plant, but in the long run, it turned out better.

Well, I hope my experience with JoePye will be more like ahughes's and not like apcohrs's. I got some blooming fairly prolifically from seed for the first time last year and certainly did not deadhead them. I'll be looking for seedlings.

I tried the suggestion of 'pinching back' (cutting back) eupatorium for sturdier more compact clumps (three large) for the first time last year...won't do that again.

It sounded like a perfect solution, especially for the clump near the outdoor unit to my heat pump that reaches the gutter of my roof line each year....but each cut produced 4 smaller stems immediately above it, resulting in many more but much smaller flower heads. Even though smaller in size, they still bent to almost the ground in a late summer rain, occasionally breaking.

I haven't noticed birds enjoying the seed heads, and mine will self seed if not deadheaded....I don't need more.

MorZ8,

You live in a much different zone than me so maybe they just grow much faster there. You may need to prune them more than once if they are growing that tall. Mine only get about 6-7 feet tall. And they need full sun.

Here's some more detail. I pruned selected branches of my eupatoriums in about june. I pruned them back a few nodes where I could see the smaller buds emerging on the side ( I remember 2, but it could have been 4). I recall they were about 3-4 feet tall at that point. The flower heads were not smaller as I recall and mine have never flopped to the ground. In fact, the stems are still standing in my garden now waiting for me to get around to removing them.

happy gardens!

From my experience, Eupatorium maculatum is one of the last perennials to emerge in the spring. Do not despair if it takes a long time emerge. A severe pruning is not enough to keep this plant down.