Well-maintained flower beds have mass appeal, and more and more gardeners are opting to plant natural borders and landscapes consisting of native perennial flowering plants. Not only do native plants help create habitat for pollinators and wildlife, but they are also able to adapt and thrive in weather conditions specific to the growing region. This is especially beneficial in regions where drought is common. The cup plant, for example, is a wildflower that can show just how advantageous planting native perennials can be.
I. Appearance and Characteristics
Silphium perfoliatum, the cup plant or cup-plant, is a species of flowering plant in the family Asteraceae, native to eastern and central North America. Silphium perfoliatum grows in sandy moist bottom lands, floodplains, near stream beds, in or adjacent to open woodland.
The typical height of S. perfoliatum plant ranges from 1–2.5 m (3–8 ft). The stem is stout, smooth, slightly hairy (glabrous) , strongly 4-angled square, like mint plants. The leaves are opposite, toothed and ovate. The petioles are widely winged and fused around the stem, forming a cup. The first flower develops on the tip of the main stem, then more flowers develop on side branches.
The flowers, which appear from midsummer to autumn (fall), look very similar to sunflowers, but are a lot smaller; measuring about 2.5 cm in diameter, with golden yellow ray florets. In the middle of the flower there are small, sterile, tubular disk florets, which are structurally bisexual, but the stamens are the only fertile part, and they do not produce seeds. The corollas are tubular, 5-toothed, and the style is undivided.
The ray florets have female characteristics, and eventually develop to become thin brown achenes with a marginal wing utilized for wind dispersal. Insect pollinators including bees, butterflies, and skippers help to cross-fertilize flowers to produce seeds. 20 to 30 seeds are created in each flower head. Each seed is about 9 to 15 mm long, 6–9 mm wide, flattened in shape, with a thickness of 1 mm.
Silphium perfoliatum is able to establish colonies due to its central taproot system and shallow rhizomes. A multi-rhizomed clone originating from a single seed is believed to be 15 years old. The roots found in botanical gardens have been estimated to be more than 50 years old. S. perfoliatum has an extensive root system and does not transplant well except when very young.
II. How to Grow and Care
Sunlight
Cup plant grows best in full sun—at least 8 hours of direct sunlight a day. Native to North American prairies, cup plant thrives in planting spots with all-day sunlight. It tolerates a few hours of shade and is known to grow at the prairie edge, near woodlands, in its native habitat.
Temperature and Humidity
As previously mentioned, the cup plant is extremely hardy and can grow in a variety of climates and locations. Its growing zones range from the cold zone 3 (last frost around May 15th and first frost around September 15th) to the very warm zone 9 (last frost date of March 1st and first frost date of December 15th).
Watering
The cup plant can tolerate heat and drought but prefers regular watering. Be careful not to overwater your cup plants.
Soil
Because the cup plant has a large native range, it can grow in a variety of soils, but best tolerates medium-to-wet soil, or soil rich in clay. If you want to achieve taller cup plants; plant them in wetter soil; if you want shorter cup plants, drier soil is best.
Fertilizing
Cup plant doesn‘t need fertilizer. Boost the nutrients in the plant’s root zone and improve soil structure by spreading a 2-inch-thick layer of compost around the plant annually in spring. The compost will break down and move into the soil profile, adding nutrients and improving texture.
Planting Instructions
Fall is the best time to plant cup plant from seed. Scatter the seeds on a prepared bed and press them lightly into the soil. Cover the entire seed bed with a loose covering of straw, and water the bed. The seeds can also be sown in spring, but they require a two-month period of cold stratification before being sown.
Plant cup plant nursery starts in early spring at the same depth as they grew in the nursery pots.
Water new seedlings and transplants regularly during the first growing season to encourage strong root development. Spread a 2-inch-thick layer of mulch over the root zone to prevent soil moisture evaporation and keep weeds at bay.
Pruning
This perennial requires no pruning. If desired, reseeding can be limited by snipping off spent flower blossoms as soon as they fade. Removing the flower blossoms eliminates the potential for the plant to produce seed.
Propagation
Because cup plants are such vigorous and expansive growers, propagation is rarely a concern. If you would like to start a new patch of cup plants, simply dig up an existing plant and transplant it elsewhere in your landscape. Water well, and the plant should propagate itself.
You can also propagate cup plants from seed as described in the steps below.
How to Grow from Seed
The easiest time to start a crop of cup plants from seed is in late fall:
- Sprinkle seeds on open soil, and gently press the seeds into the soil.
- Cover the area with a light layer of straw to help retain moisture and prevent birds from eating the seeds.
If you’d like to plant in the spring, you’ll need to stratify (chill ) the seeds for 60 days before planting:
- Mix the seeds with moist sand and place them in a refrigerator or a cold location outdoors.
- After 60 days, in early spring, plant your seeds and keep the soil moist to ensure germination.
Pests and Diseases
Cup plant has no notable pests, but it reseeds aggressively unless it is deadheaded. Seedlings are usually easy to pull out of the ground when they are young. Established plants have an extensive, fibrous root system and are more challenging to eradicate. Remove unwanted seedlings as soon as possible.
III. Uses and Benefits
- Use as ornamental tree
Cup plant is grown in sunny spots in dry, warm gardens for its beautiful flowers, vigorous growth, and attractiveness to pollinators. It makes an excellent centerpiece or backdrop plant in butterfly gardens, looks great in wildflower gardens and is perfect for a prairie garden.
- Use as energy crop
Silphium perfoliatum is considered a potential energy crop plant, especially because it has low demands on the climate, the soil and previous crop and produces high amounts of biomass. Based on the results of the Thuringian State Institute of Agriculture the plant can be an alternative plant for biogas production. The annual biomass yields are very different according to the present literature: In the second cultivation year S. perfoliatumcan grow from 13 to 20 tons of biomass per hectare, an experiment done in Thüringen, Germany even showed that 18 to 28 tons of dry weight per hectare are possible.
- Use as animal fodder
Although its use as an energy crop prevails, S. perfoliatum can also be used as a fodder plant thanks to its ingredients. S. perfoliatum contains amino acids, carbohydrates (inulin in rhizomes), L-ascorbic acid, terpenes with essential oils, triterpene saponins, carotenoids, phenolic acid, tannins, and flavonoids. The cup plant is considered to have a high feed value for meat and milk producing farm animals because of its longevity and high protein levels. S. perfoliatum can be stored as silage. It is recommended to harvest the plant twice a year. Otherwise, the stem gets too tough due to the high content of fibre. The high water content at the first cutting in June is not a problem when letting the plant wilt shortly.
The blooming period of S. perfoliatum takes eight or more weeks. The long blooming period and abundance of flowers provides a rich source for bees and the cultivation of honey. The honey is rich in fructose and crystalizes therefore only slowly. 150 kg honey per hectare and year are reported as a possible yield from a cup plant field.
- Use for medical purposes
S. perfoliatum produces a resin that has an odor similar to turpentine. The plant contains a gum and resin; the root has been used medicinally. The resin has been made into chewing gum to prevent nausea and vomiting. Native Americans would cut off the top of the plant stalk and collect the resinous sap that was emitted from the plant. The resin was used for a chewing gum to freshen the breath. The Winnebagos Tribe believed that a potion made from the rhizome would provide supernatural powers. The people belonging to the tribe would drink this potion before hunting. The people of the Chippewas tribe used the root extract for back and chest pains, to prevent excessive menstruation, and to treat lung hemorrhage. During the spring, the tender young leaves were cultivated as an acceptable food source by cooking or a salad.
The powdered form of S. perfoliatum has diaphoretic and tonic properties. It can help alleviate the symptoms of fevers, dry cough, asthma, spleen illness, heart and liver disease. The extract from the leaves of the plant has shown to lower cholesterol and triglycerides levels in blood. Studies show that the presence of phenolic acids is responsible for the species’ antiseptic activity to stimulate generation of IgG and IgM antibodies. In addition, it stimulates bile production of the gallbladder.
- Use as pollinator and bird-friendly ornamental garden plants
The flowers of S. perfoliatum make it an attractive plant for many pollinators, the seeds along with the “cups” of water, formed along the stems, are attractive to birds as a food and water source. During the 1750s, the species was introduced to the United Kingdom and the Soviet Union, and has been prized as an ornamental plant since. It was named in 1759 by Carl Linnaeus. In the UK it has gained the Royal Horticultural Society’s Award of Garden Merit.
Silphium perfoliatum is sold by a good number of native plant nurseries and some specialty nurseries in the US and Canada; rarely in conventional nurseries. It is often used in prairie and native meadow restorations and in native, naturalistic landscapes and gardens; only infrequently in conventional landscapes and gardens by landscape designers and architects that know of it as a unique looking perennial. A large patch was planted at Millennium Park in Chicago, Illinois, near the Lurie Garden, in 2010. In gardening and landscaping it is best used in groups and not individually, as it is so vertical and the flower stalks are more likely to fall over when grown singularly.
Find Where to Buy the Best Cup Plant (Silphium perfoliatum)
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