Silphium perfoliatum
cup plant
compoSitae
3-in.-wide yellow daisies on tall stalks;
pairs of coarsely toothed leaves that form
cups around the stems
5–9 ft. high; 2–3 ft. wide
Full sun–light shade
Blooms July–September
Zones 3–8
pruning Cup plant can self-sow
abundantly. You may want to curb
reseeding by deadheading, but
because the seed is a finch favorite, a
better plan might be to only plant this
overenthusiastic prairie native in
spacious naturalistic gardens where it
has permission to spread. Plants may
lean or bend in strong storms but can
be made sturdier by cutting them back
by half when they reach about 4 ft. tall.
Bloom time won’t be delayed if
trimming is accomplished bymid-June. Cleanup of dead stems is
most easily accomplished by waiting
until late winter or early spring if
winter weather persists. By then the
stalks will have dried completely and
may be cleanly snapped off at the base
and carted away to the compost pile.
Any remaining debris may be left in
place to decompose.
other maintenance Cup plant
prefers more moisture than other
Silphium species, and its lower leaves
will turn brown and begin to drop if it
becomes drought stressed. It tolerates
a bit of shade but is best in full sun.
This plant spreads by rhizomes as well
as by seed and may need to be con-
tained by regular mowing around the
planting perimeter or by roguing out
unwanted plants. The hordes of
butterflies it brings to the garden
(especially tiger swallowtails) make it
worth the effort to maintain.Silphium perfoliatum