Stylophorum diphyllum or wood poppy is a prolific seeder in our climate, but a nice woodland plant. Seedlings germinate on their own & are winter hardy. I don't know if it can shade out grasses since it prefers some shade & moisture.

The bright gold blooms really shine in the spring garden especially when combined with a blue flower like columbine or blue-eyed Mary since they both bloom at the same time. After that 1st flush of flowers has faded & the weather turned dry in July I cut it back hard. It regrows nice foliage & blooms again some, but not like in spring.

There is a orange flowering one that isn't as nice. I've read that the orange will eventually take over the yellow if you have both. The orange is a bit loud, but might suit you.

There is a taller wildflower poppy, Chelidonium majus with coarser leaves & smaller flowers. I like wildflowers, but this one is way to weedy. You don't want it.

At garden swaps often the 2 are switched, so you have to be careful. That is how I got each of them from 3 different sources. With a plant in back & front yards I'm set for life! It will just take one plant for you to get started or seeds.

Corrine

Here is a link that might be useful: good photo

Make sure you are planting stylophorum and not Welsh poppy or Meconopsis cambrica. Welsh poppy, which comes in both yellow and orange flowered forms, is pretty much a weed. Seeds prolifically, grows well under a wide range of light and soil conditions and is extremely difficult to remove because of stubborn taproot. Stylophorum or celandine/wood poppy is present in only yellow flowers.

IME, Welsh poppy is not a clumper but grows more like other annual poppies like Papaver somniferum or Papaver rhoeas - tallish but narrow plants. Not at all very useful for shading out weeds or weedy grasses! The wood poppy is a much better choice for that but really needs a more shady location to flourish.

If growing either the solidagao or stylophorum from seed, I would recommed direct sowing. No babying required!

Are there 3 different yellow wood poppies or are two of these the same plant?

Meconopsis cambrica
Stylophorum diphyllum
Chelidonium majus

They're all different.

The locally wild goldenrod does not show up that well in bloom. A garden form would probably be a better choice, maybe the bigeneric X Solidaster luteus as with that you get a bit more daisy-like individual flower head as well.

I'm getting some plants, named varieties, and also some Goldenrod seeds to try out. I'll let you know how they do. I'm somewhat afraid of the Goldenrods being eaten by deer so may have most behind fencing, but the ones from seed I will try in the open.

Nancy

Deer haven't nubbled on Goldenrod Fireworks here. Seedlings are attractive to slugs like any other.

Thanks, Corrine, Solidago is on lists of plants deer don't bother much, but I've also seen websites that sound like deer may eat them in a pinch.