Rain Garden Plant Guide Part I: The Best Perennials for Damp Conditions

When it comes to designing a rain garden, selecting the right plants is essential. These plants not only thrive in wet conditions but also contribute to the overall beauty and functionality of the garden. In this post, I will introduce you to a variety of perennial options that are my go-to's for garden beds that maintain moist-to-wet conditions (I.e., are next to a downspout, or are the low spot of a garden, etc.). Since light conditions are just as critical in plant selection, I've listed this with each plant to help you narrow down which ones will work for your space. Let's dive in!

Lobelia cardinalis (Cardinal Flower)

Conditions: Prefers moist to wet soil and thrives in full sun to part shade.

With its striking red blooms and tall, upright growth, the cardinal flower adds a vibrant splash of color to any rain garden. This native perennial also attracts hummingbirds and butterflies, making it a delightful addition to your garden ecosystem.

Lobelia cardinalis is perfectly suited for consistently damp, part-shade sites like this rain garden in Atlanta. Image courtesy Staghorn NYC.

Asclepias incarnata (Swamp Milkweed)

Conditions: Flourishes in moist to wet soil and thrives in full sun to part shade.

Asclepias incarnata, also known as swamp milkweed, is a native plant that supports pollinators like butterflies and bees (including Monarch butterflies). Its pink blooms arrive in mid-summer and at roughly 4' tall, these leggy plants are perfect in the middle and back portions of a border.

I have swamp milkweed planted near two different sunny downspouts in the front garden at Winterhill and they are thriving! It's a joy watching the Monarch butterflies flock to them.

Rudbeckia fulgida (Black-Eyed Susan)

Conditions: Adapts well to a variety of soil conditions, including both wet and dry areas, and thrives in full sun and can take part shade.

The cheerful yellow blooms of Rudbeckia fulgida are one of my favorite signals that summer is here. These drought-tolerant plants attract tons of pollinators and are known for their long-lasting flowers, adding a burst of color from June into September. I love pairing them with ornamental grasses for an instant meadow-effect.

Nothing says "summer" like Rudbeckia. This perennial is so easy going in both damp and dry conditions. Here it is in the front garden at Winterhill.

Astilbe chinensis (False Spirea)

Conditions: Enjoys consistently moist soil and thrives in part shade to full shade.

Astilbes are known for their feathery plumes of flowers, which come in a range of colors from soft pinks to vibrant reds. These shade-loving shrubs add texture and dimension to rain gardens while providing a pop of color in areas with less sunlight. I love Astilbe "Pumila" for a lower-growing variety with lavender flowers or "Delft Lace" for a larger variety with burgundy-tinged foliage and pink flowers.

Astilbe "Pumila" is a great shade/part-shade perennial for the front of the border. Image courtesy iStock.

Iris versicolor (Blue Flag Iris)

Conditions: Enjoys moist soil; does well in full sun to part shade.

Our native blue flag iris displays elegant blue or purple blooms that add a touch of sophistication to any rain garden. With its sword-like foliage and striking late-spring flowers this iris variety provides vertical interest - almost like an ornamental grass when not in bloom - and thrives in wet conditions.

Blue flag iris is often found growing wild nexts to streams, rivers and ponds, but will happily grow in your garden as well. Image courtesy Gardenia.net.

Chelone glabra (Turtlehead)

Conditions: Flourishes in moist to wet soil and thrives in full sun to part shade.

Chelone, also known as turtlehead, boasts unique snapdragon-like flowers that resemble the head of a turtle. Its late-summer blooms and glossy foliage provide visual interest, while also attracting pollinators like butterflies.

Chelone "Hot Lips" brings vibrant pink blooms to the shady parts of the front garden at Winterhill in late summer.

Eupatorium purpureum (Joe Pye Weed)

Conditions: Prefers moist to wet soil and thrives in full sun to part shade.

Joe Pye weed is a tall, native perennial with clusters of mauve-pink flowers that bloom in late summer into fall. It attracts butterflies and other pollinators, and its robust growth and architectural form make it a striking addition to rain gardens. I love the height and drama these bring to the back of the border.

A beautiful behemoth. If space allows, Joe Pye Weed brings so much volume and character to a garden bed. Image courtesy Staghorn NYC.

Carex muskingumensis (Palm Sedge)

Conditions: Adapts well to various soil conditions, including wet areas, and thrives in part shade to full sun.

Carex, or sedge, is a versatile plant with numerous varieties that offer different colors and textures. It is an excellent choice for rain gardens due to its ability to retain moisture and prevent erosion. Palm sedge is particularly well-suited to damp, shadier areas that need quick coverage for weed suppression and erosion control.

Palm sedge grows in dense colonies providing a helpful groundcover in shady, damp areas where other plants may not take well. Image courtesy Knoll Gardens.

Juncus (Rush)

Conditions: Thrives in consistently moist to wet soil and tolerates full sun to part shade. Juncus, commonly known as rush, is a grass-like perennial that adds a textural and architectural element to rain gardens. Its cylindrical stems and attractive seed heads provide visual interest and help stabilize the soil. Like palm sedge, this is an ideal option when quick coverage for weed suppression and erosion control is needed.

Dark green juncus has perfectly upright foliage and is incredibly tolerant of damp spaces. Image courtesy Hoffman Nursery.

By incorporating these perennials into your rain garden, you can create a beautiful and functional landscape that thrives in wet conditions. Remember to consider the specific requirements of each plant and their compatibility with your local climate, sun and soil conditions. Happy gardening!

A rain garden I designed for my brother and sister-in-law in Atlanta. I've put all of these plantings listed below to the test! Image courtesy Staghorn NYC.

This rain garden often gets fully submerged by large rainstorms in spring and summer.