Cup Plant: A Plant You Can Look Up To
Judy and I like tall perennials, and we have lots of them in the garden. I mean really tall, like you have to look up to see the flowers. We’ve considered starting an organization for ourselves and others who admire towering plants. It could be called the American Prodigiously Tall Plant Society (APTaPS).
Anyhow, of all our really tall perennials, the absolute tallest is the Cup Plant (Silphium perfoliatum). In our garden, it grows a to a good 10′. If you look at the leaves at the bottom of this picture, you can see how the leaves are perfoliate – the main stem passes right through them. As a result, the leaves form cups that catch rainwater – hence the common name.
Late July and August is when Cup Plant is topped by bunches of yellow daisy-like flowers,
We have a patch of Cup Plant at the back of our Front Island Bed. At this time of year it blooms with Sweet Joe Pye Weed (Eutrochium purpureum) and ‘Purple Rooster’ Bee Blam (Monarda didyma).
Cup Plant has a reputation as a thug but I do not find it difficult to control. Sure, you will find volunteers popping up here and there but I just yank them out of the ground or cut them at the base. It’s really a gentle giant.
Cup Plant is very beneficial for wildlife. The flowers attract bumblebees, native bees, honey bees, and predators of insect pests. Some native bee species nest in the hollow stems. After the flowers fade, Goldfinches come to feast on the seeds.
Not surprisingly, given its height, Cup Plant needs some support in our garden. I use rebar for stakes and lots of green twine.
Some gardeners are put off by Cup Plant’s size and enthusiastic self-sowing. Not us. We love its dramatic height and the giant contribution it makes to wildlife habitat in the garden.