In Defense of Cup Plant
Just recently I read an informative post entitled “3 Problematic Plants in Native Plant Gardens and 3 Native Alternatives”. The post was on the Facebook page of Indigenous Landscapes, a native plant landscaping company based in Cincinnati. While the arguments made in the post were reasonable, I had a somewhat different take on the plants in question.
First, the authors recommend Aromatic Aster (Symphiotrichum oblongifolium) as a substitute for New England Aster (S. novae-angliae). Aromatic Aster, they argue, has a much neater and tidier habit than its New England cousin.
Certainly it is true that the straight species New England Aster can be very tall, gangly and bare-kneed. Even after being cut back, I find that it needs staking. One way to deal with this, of course, is to put it behind shorter plants.
In my experience Aromatic Aster is rather short-lived in soil that is rich and moist, where it can also get just a bit gangly and floppy, though not nearly to the same extent as New England Aster. Under these conditions, I would go with Short’s Aster (S. shortii), which has a shrubby, upright habit and abundant blue flowers. Short’s Aster will also tolerate a fair amount of shade.
One problem with Short’s Aster, though, is that it is hard to find – the only place I know of where it is available is Prairie Moon Nursery.
The authors also recommend Prairie Dock (Silphium terebinthinaceum) as a substitute for Cup Plant (S. perfoliatum). Both these plants are extraordinarily tall. They argue that Prairie Dock is less likely to flop and self-sows less aggressively than Cup Plant. What’s more, Prairie Dock has big striking leaves at the base and tall, almost leafless stems that give the upper part of the plant a transparent quality.
This is a valid argument to an extent, but I would argue that if Cup Plant is too big for someone’s garden, the odds are decent that Prairie Dock is as well. To be honest, to my eye Prairie Dock has an almost skeletal look which is not always appealing.
In our garden, I have not found Cup Plant terribly difficult to control, though it certainly can self-sow. And it can require staking to keep it upright, but that’s something I’m willing to live with in exchange for its many virtues – particularly the bold leaves that create small pools of rainwater, of great value to wildlife, where they clasp the stout stems.
Cup Plant does nicely placed behind plants that are tall but not towering. In our garden we have it growing behind New England Aster.
If the Silphiums are too overpowering for a smaller garden, an alternative to consider is Early (or Ox Eye) Sunflower (Heliopsis helianthoides), a bushy plant that only grows 3-6 feet tall.
Finally, the folks from Indigenous Landscapes recommend Showy Goldenrod (Solidago speciosa) as a replacement for Canada Goldenrod (S. canadensis). Not that anyone ever plants Canada Goldenrod, but it will sometimes crash the garden party on its own.
I have no quarrel with this suggestion, but I would mention two others that are shorter have more shade tolerance: Bluestem Goldenrod (S. caesia) and Anise Scented Goldenrod (S. odora). Of these, Bluestem Goldenrod has flowers spread along arching stems, Anise Scented Goldenrod is more upright.
Would you plant Cup Plant in your garden? What about Prairie Dock or New England Aster?