Known for their yellow blooms, coarse leaves, and super long stems, cup plants attract butterflies, birds, bees, and other beneficial insects throughout the growing season, or July through September. If you’re wondering where the name “cup plant” comes from, look closely at the plant’s leaves—they form a small basin that enables water to pool around the stem. It’s not uncommon to see birds and other animals or insects sipping water from these tiny basins on a hot day. The cup plant is a large plant that requires ample growing space and may overwhelm smaller plants. Although the cup plant can appear weed-like to some gardeners, it is well-suited for prairies, wildflower gardens, naturalized areas, or bordering a stream or pond. Fortunately, cup plants are generally resistant to serious insect infestations or diseases. Large crops of cup plants may be susceptible to the fungus Sclerotinia, but it’s rare in gardens.
Light
Although cup plants are extremely hardy, six to eight hours of full sun is recommended for optimal growth. If full sun isn’t available, the cup plant can thrive in partial sun, too. If you live in a colder zone, consider planting your cup plants in a spot with full sun and little to no wind.
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.
Water
The cup plant can tolerate heat and drought but prefers regular watering. Be careful not to overwater your cup plants.
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).
Fertilizer
Thanks to its hardiness, commercial fertilization isn’t required for cup plants in gardens, prairies, or naturalized areas. If you want to give your cup plants additional protection, opt for compost or composted manure as a drop dressing on the roots. In larger crops, fertilizing is recommended as early as possible during the first year of the cup plant’s growth to protect the roots. Some studies of larger cup plant crops have shown that fertilizing is not required in the cup plant’s second year.
Types of Cup Plants
There are two recognized varieties of the cup plant:
Connatum (hairy stems; found in a handful of mid-Atlantic states)Perfoliatum (extremely common throughout the central and southern United States)
Propagating Cup Plants
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 Cup Plants From Seed
The easiest time to start a crop of cup plants from seed is in late fall: If you’d like to plant in the spring, you’ll need to stratify (chill ) the seeds for 60 days before planting:
