We have a large collection of silphiums at JLBG, but unfortunately most have limited garden value since they splay apart and often completely fall over when in flower. While they’re loved by native bees, we have been frustrated to not find many that are mainstream garden worthy. One that has been impressive in our trials, however, is the southeast US native whorled rosinweed, Silphium trifoliatum var. latifolium. These 15 year-old clumps at JLBG, which originated from Scott County, Mississippi are now 6-7′ tall, and quite garden worthy. Hardiness Zone 5a-8b, at least.
Being a non-Latin guy, I know the plant by its common name of cup plant since rain water will accumulate in the junction of the leaves and the stem. It can flop if it is planted by itself or at the edge of a bed. I have it in a 30×80 prairie garden. It flops at the edges but in the middle with the support of other prairie plants it remains upright. I also notice that the older cup plants are stronger and less prone to flop. From my perspective the downside of the plant is it is a prolific seeder and has to be managed by dead heading or removal of seedlings. Bees and butterflies absolutely love the plant and finches eat the seeds. I wish the finches would eat more.
Yes, the common name cup plant is used for the species, Silphium perfoliatum. Most other species don’t form a cup where the leaves emerge from the stem.
Cup plant is a common name for the species Silphium perfoliatum or S. connatum. The other species don’t form a cup, so the common name wouldn’t exactly fit. You might surprise yourself by knowing that you use Latin names ever day. Homo sapiens ‘John Jones’ is a trinomial Latin name with Genus, species, and Cultivar. Unless of course you stick to common names for people also, like, Hey, you with the brown hair or you with the large stomach, etc. Of course plant Latin names we’ve heard before seem to be fine because we don’t realize they are Latin. These include Iris, Geranium, Impatiens, Camellia, Hydrangea, Begonia, Lantana, etc. So, it’s only Latin names that people have never heard before that seems to be problematic…at least from our perspective.
This is truly a magnificient plant! How would I go about getting some seed from this to use in a seed bulking prairie restoration project in WI? I know we’re a few zones off from you, however, planning for a warmer future isn’t the worst idea.
We have sizable beds for numerous species that will be used for seed generation that will ultimately provide genetic diversity for a several hundred acre restoration. We would appreciate any assistance for Silphiums in general, but this particular plant would be amazing!
I’m not sure where you might find seed. We don’t grow any silphiums from garden seed because they interbreed so much.
Is there anyway to get a few seed heads from this plant?
They have already been cut for the year.