The Cup Plant, Silphium perfoliatum, is a beautiful plant native to large areas in the central and eastern US and to Ontario and Quebec in Canada. Its large stature, (6 to 9 feet tall) and wide, tapered leaves are further complemented by an abundance of open yellow flowers. The flowers will re-bloom well into the autumn.
Quick Growing Guide
Botanical Name: Silphium perfoliatum
Botanical Family: Asteraceae
En français: Silphie perfoliée
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Sun / Shade:
Water: Dry to Moist
Cup Plant can be cultivated in a native ecological habitat and can create a full perennial hedge. It appeals to humans as well as animals. During the hot summer months, the stunning, huge yellow flowers, which resemble sunflowers or large yellow asters, will bloom (July-September). This natural plant, which is unusual for perennials, can provide privacy when in bloom. This low-maintenance plant is also an excellent addition to a rain garden.
Silphium perfoliatum Appearance
By August, the Cup Plant is very tall, growing up to 8 to 10 feet tall under ideal circumstances. The topmost short stalks with several flowers will be the only branches. Large, coarse teeth are seen on the lanceolate leaves that line the stalk. The flower looks a lot like a typical sunflower. Their diameter ranges from 3 to 5 inches. Each flower has 20–40 petals, some of which are not closely clustered and have gaps.
It is a large plant that needs lots of space. Some gardeners find it to be an effective backdrop for other perennials. It adapts well to prairies, wildflower and native plant gardens, naturalized areas, or moist, open woodland areas, including stream and pond edges.
Cup Plant Care
Cup Plant is easily grown in average, medium to wet soils in full sun; it tolerates some drought once established. It is somewhat slow to establish when grown from seed. It self-seeds in optimum growing conditions.
Growing your plant from seeds is advised because the cup plant is seen as a weed-like plant by many gardeners and gardening supply stores (it may be difficult to find a plant in your local garden center). Planting outside in the fall is the best time to start from scratch, but spring planting is still an option.
Before planting the seeds, be sure you’ll have a complete 60 days of cold stratification. After sprouting from seeds, cup plants probably won’t bloom until at least their second year of development. Keep the cup plant well-watered and weed-free throughout this time.
The cup plant can thrive in a wide range of soils due to its extensive natural range, but it prefers clay-rich or medium-to-wet soil. Plant them in moist soil if you want taller cup plants; dry soil is ideal if you want shorter cup plants.
Watering Cup Plant
Although the cup plant can withstand heat and dryness, it loves routine watering. Don’t give your cup plants too much water.
Cup Plant Light Needs
Despite cup plants’ great hardiness, six to eight hours of direct sunlight daily are advised for optimum growth. The cup plant can also grow in partial sunlight if full sun is not possible. Consider placing your cup plants in a location with ample sun and little to no wind if you live in a chilly climate.
Temperature and Humidity
As noted before, the cup plant is incredibly resilient and may flourish in a range of environments. Its growing regions span from the relatively warm zone 9 to the frigid zone 3.
Cup plants in gardens, prairies, or naturalized regions don’t require commercial fertilizing due of their hardiness. If you want to give your cup plants more defense, choose compost or composted manure as a drop dressing on the roots.
Pests and Problems
There are no serious illnesses or pests that affect cup plants. The stems of the leaves will serve as a feeding ground for local fauna, such as the gall wasp. The plant’s health won’t be harmed by this, but it might draw a parasitic wasp.
Strong gusts may cause it to topple over because it is a tall, lanky plant. Additionally, the weight of the flowers may cause this. You can either let the plant alone or try to stake it because this is a typical trait of the plant.
Relation with Nature
The flowers of cup plants offer native bees a delicious feast as well as a stable construction and ingredients for nesting. Native populations can use the water collected in the cup-shaped leaves as a birdbath, and the huge seed head is highly alluring to birds. Hummingbirds, monarchs, skippers, moths, and a variety of bees, wasps, and bee flies are attracted to cup plants. Gold Finches are known to huddle in the thick stems and drink water from the cups.
Any grassland, wooded area, bank, or butterfly garden would benefit from the inclusion of cup plants. A perennial that grows to a large (tall) size adds a strong vertical accent to any space. The blooms will continue into September when the plant is encouraged to set seed by the colder evenings and will open in a manner resembling a sunflower. The 8′ height of the Cup Plant gives it the ability to overcrowd a smaller perennial garden. A big stalk will be supported by a core taproot, which will also spread by shallow rhizomes to support vegetative reproduction.
The term “cup plant” refers to the plant’s appearance, specifically its central leaves. You can observe that the opposite leaves are joined to form a cup and that there are no petioles. Insects and birds will use this cup to collect rainwater for drinking and nesting.