When selecting perennials, choosing plants that are suitable for the site is important. Garden sites can vary tremendously. Some areas are hot and dry. Others are wet. Wet sites can be challenging, but they also provide gardening opportunities. The following perennials perform well in moist to wet soils.
Jack-in-the-pulpit (Arisaema triphyllum) is a native woodland wildflower. It is commonly found in moist woodland sites. Jack-in-the-pulpit consists of 1 or 2 three leaflet leaves and a separate flower stalk. The flower structure consists of a club-like spadix (the preacher or Jack ) and a leaf-like spathe (pulpit), which curves up and over the spadix. The spathe may be green, purple-brown, or striped. A cluster of berries develops after flowering. These berries turn bright red in fall.
Goat's beard (Aruncus dioicus) is another native woodland wildflower. Goat's beard grows 4 to 6 feet tall and 6 feet wide. Its pinnately compound leaves are 2 to 3 feet long. Dense spikes of creamy white flowers are produced in early summer. Goats's beard performs best in partial shade. In the home landscape, goat's beard is best used as a background plant because of its large size.
The flowers of turtlehead (Chelone species) somewhat resemble a turtle's head. Chelone glabra is native to Iowa and produces white flowers. Chelone lyonii has rose-pink flowers. Both plant species grow 2 to 3 feet tall. Turtlehead prefers moist to wet soils in partial shade.
Black snakeroot (Actaea racemosa syn. Cimicifuga racemosa) is an erect 4- to 6-foot-tall plant that blooms mid-summer. The small, white flowers are borne on 2- to 3-foot-long, wand-like flower stalks. Black snakeroot performs best in moist, shady locations. Other common names include black cohosh and bugbane.
A tall, spectacular plant of moist prairies is queen-of-the-prairie (Filipendula rubra). It produces large, fluffy flower plumes in June through July. The individual flowers are 1/4 to 1/2 inch in diameter and peach to pink. Plants grow 6 to 8 feet tall. Its large size makes it unsuitable for small gardens. Queen-of-the-prairie performs best in cool, moist, partially shaded locations. 'Venusta' is a widely grown variety with deep pink flowers.
Japanese iris (Iris ensata) flowers in early to mid-summer. The large, flat flowers may be up to 10 inches wide. Numerous cultivars are available. Flower colors include white, blue, purple, reddish-purple, and lavender pink. The flowers often have veins, stripes, or blotches of a contrasting color. Japanese iris requires moist, acid soils. It grows in partial to full sun. Compared to bearded iris, Japanese iris has few insect or disease problems.
Yellow flag (Iris pseudacorus) has sword-shaped leaves and blooms in late spring. The light yellow flowers have brown blotches on their falls. Yellow flag is an excellent plant for wet areas along streams and ponds. It performs best in moist to wet soils in partial shade to full sun. Plants may grow 3 to 4 feet tall when provided ideal growing conditions. In spring, the newly emerged leaves of 'Variegata' have yellow stripes. The variegation gradually disappears by mid-summer.
Cord grass (Spartina pectinata) is a native prairie grass. It is a tall, warm-season, perennial grass usually found in wet prairies. Cord grass normally grows 4 to 6 feet tall but can grow up to 10 feet tall in favorable sites. Cord grass spreads aggressively via underground stems or rhizomes. Its spreading, aggressive nature makes cord grass a poor choice for small gardens. However, it can be effectively used on steep banks and along lakes for erosion control. The leaf blades of 'Aureo-marginata' have yellow margins.
Several species of spiderwort (Tradescantia) are native to Iowa. Plants have grass-like foliage and produce clusters of blue to purple, occasionally white or pink, flowers. Though individual flowers last only one day, spiderworts continue to bloom for several weeks from late spring to mid-summer. Spiderworts are easy to grow. They perform well in full sun to partial shade and moist to wet soils. Several hybrid cultivars are available. These cultivars are better than the native species for landscaping purposes. The native species freely reseed themselves and often become weedy in perennial beds. The cultivated varieties are more restrained.
Other Perennials for Wet Conditions
Other perennials suitable for moist to wet soils include:
- swamp milkweed (Asclepias incarnata)
- marsh marigold (Caltha palustris)
- rose mallow (Hibiscus moscheutos)
- globeflower (Trollius europaeus)
- Ferns (various species)