It looks like Filipendula probably Ulmaria to me

It looks like Filipendula ulmaria which is native to damp meadows in Europe and western Asia. It's pretty but seeds around a lot.

Woodyoak and maet gave you the latin name for your plant. The common name for it is Meadow sweet and it is a native wildflower.

I looked it up in Petersons guide to Wild flowers and here's part of what it said--It is in the rose family. It is found in old fields, meadows, roadsides and low ground. Native to the area of Michigan to Newfoundland, south to New England, Long Island to north Carolina

I think Filipendua rubra is the native one.

Thank you very much for such prompt responses. I googled it - it is meadowsweet indeed!

Goodle says: Although native to Europe and Asia, this species has escaped gardens and naturalized in parts of eastern North America.

What does that mean? Is it OK to introduce it into the forest then or not?

It is not F ulmaria - that has pinnate leaves, not palmate, so entirely different from the plant in the photograph. F ulmaria isn't a US native. As woodyoak says, that one is F rubra which comes with pink, pinkish white or white flowers.

Here is a link that might be useful: F ulmaria leaves - pinnate.

floral UK - you are probably right - it's more likely to be Siberian meadowsweet (Filipendula palmata) based on the leaves, but it's often sold here as F. ulmaria - that's certainly what the tags for mine say.

F ulmaria is our native meadowsweet, so I know it well and and I have it by my microscopic garden pond. I grew my plants from seed gather along the local canal.

Here is a link that might be useful: F ulmaria

"Goodle says: Although native to Europe and Asia, this species has escaped gardens and naturalized in parts of eastern North America.

What does that mean? Is it OK to introduce it into the forest then or not?"

If you don't like this plant don't feel bad about tossing it. It has adapted well here but it is NOT a US native.

green_go - if a plant isn't native, you always run the risk of introducing something which may become invasive in your garden conditions. Once you factor in moisture, soil components and natural predators, it's always wisest to think twice before planting something unless experience has shown that it behaves in your garden.

Certain native species can also run rampant when planted in areas where they aren't traditionally native.

Have I erred when planting certain perennials after hints on this forum suggested they were invasive? Let me count the number of self-sown seedlings I've regretted.

I've no experience with Filipendula since I've never been tempted to plant it. I just make certain I've done my homework before digging a planting hole or setting something in it. Not planting something has been my guide and = less regrets.

F. ulmaria has been an aggressive spreader/reseeder in my garden since the evil day I planted it years ago. I've dug out most of the plants, but have to battle the remainder in damp sections of the garden every year.

Attractive only for a short period, plagued by Japanese beetles, invasive...what's not to like?

In that case it's lucky the OP's plant is definitely not Filipendula ulmaria.