That's good to know. I was under the impression they can take drier soils - maybe I was thinking of another plant. The place I bought it from has it in display gardens and it is a monster -- something like 8 or 9 foot tall -- wonder if the conditions are optimal/moist there. But, if there's a chance it might get ratty I probably don't want it too close to the house in front of the utility pole.

My ratty one is in full day sun, cruddy clay, and we can go weeks without rain sometimes in the summer. SO... you conditions might be different.

What nevermore said - every seed will take root, which is fine if you have room. Once the flowers are pollinated, like most tall plants, the stems start to fall to the ground, so another crop of cup plants will grow that 7 to 8 feet away. I tell you this so that you don't plant it by a path or road. If you can give cup plant room, you will have the happiest bees around.

I had one for many years but I always cut it down before it set seed. Good way to manage it.

Agree with lisanti — don’t worry too much about siting it, since the seeds will decide where they want to be. I think I started with one about five years back — in a dry spot in mostly sun — and now there are four big clusters (not counting what I’ve pulled,) all in similar conditions.

I had mine up against the south side of our old house and it did well it was pretty cool, the leaves do hold water, the finches and smaller birds would drink from the cups. Where did you find yours, I’d love to get this again!

Got mine at a local nursery - doesn't ship.

Prairiemoon does carry it, they have bare roots in right now: https://www.prairiemoon.com/silphium-perfoliatum-cup-plant-prairie-moon-nursery.html

Thank you!

Many native plant nurseries carry it, especially those specializing in plants for pollinators.

2024 update: I ended up moving mine to the pasture (aka the meadow) two years ago, it never made an appearance last year so I thought it was a goner. I was back there this week and noticed what I'm pretty sure is the cup plant based on the leaves and the resolutely square stems. DH cut the meadow until beginning of June, so this thing is only about a foot tall heading into mid-June, but I'm hoping the roots now have a good foothold and it will thrive back there.

My Cup Plant is the size of an army tank. I was planning on chopping it down, but I noticed it was covered in cicadas. Hopefully their larvae will do the job for me. Silphium species self sow all over the place, and the seedings put down deep roots immediately, and require a trowel to remove. They probably aren't as much a nuicence in a meadow or prairie where there isn't any open, disturbed ground. I guess my giant cupplant stays and I won't commit cicadacide. I'm growing Cup Plant, Prairie Dock, Compass Plant, Rosinweed, and I have seedlings of Cut-leaved Prairie Dock, Silphium pinnatifidum. Silphiums often hybridize, and sometimes Cut-leaved Prairie Dock can be confused with a Prairie Dock/Compass Plant hybrid. The leaves on the Prairie Dock and Compass Plant are just as bizarre, unusual and cool as any exotic tropical.

I left the S. perfoliatum behind at my old place, but I moved some of the S. gracile--smaller and better for a smaller garden. It moved from dry sand to heavy wet clay and is happy in both places.

Many years ago I had it smack up against the house. It did well, 8’ or so, but it got too big, so I donated it to a charity plant sale, with the message that it needs room ;-). I never saw birds drinking, but that was because of the location. There was the occasional wasp. Just noticed it Saturday at a local nursery, in an area marked "native plants".

I have tried to grow this (in my prairie phase) but I think it was offended by the dry and not very deep soil on offer. Failed (along with a longish list of coreopsis, beggarticks, rudbeckias, Joe Pye etc etc.). Came to my senses though, Just because a plant is going through a fashion phase (and boy, did we all go in for prairie plantings, Oudolf styling and so on,here in the UK)...doesn't mean you can sow it and hope.

And, of course, space (lack of) is definitely an issue. Possibly somewhere out on the fen but really, plant colonialism is potentially a bit dodgy in rural places.

I got one out in the gardenyard. It came from a friends garden, I could go back and remove the rest if I wanted, heh. It's taken a couple years for it to really settle in, this year it's finally growing well. I hope it gets huge and eats up that whole niche I put it in. It is in line with a downslope and water movement across the gardenyard, and in full sun.

July Update: I am disappointed to report what I thought was cup plant is not a cup plant. It's something else with square stems and similar stems. A lot of this stuff looks alike until it blooms.