Whorled Marsh Pennywort

Year-round

Whorled marshpennywort is a wetland plant that is native to Tennessee. In the Memphis area it belongs in a pond edge, bog garden, or water-filled container, not regular garden soil, and it wants to stay wet or sit in an inch or two of water all year.

• It is native to Tennessee, so it fits naturally into wetland edges, rain gardens, and pond margins in the Memphis area.
• Keep the soil wet or standing in up to about four inches of water. Letting it dry out is the main way to lose this plant.
• It grows in sun to part shade, so either a sunny pond edge or a partly shaded bog garden spot will work.
• It is a fast spreader that grows by runners along the water surface, so give it a container or a defined edge if you want to keep it contained.
• Trim stems back with scissors any time it gets leggy. Cutting encourages thicker, bushier growth instead of long runners.

Fall

As nights cool into October and November, whorled marshpennywort slows down and heads into dormancy. This is the time to stop feeding it and tidy it up before Memphis's first frost, usually around November 3.

• Memphis's average first fall frost lands around November 3, so plan your last major trim and any plant moves before then.
• Stop fertilizing by early fall. That tells the plant to put energy into its roots instead of new top growth heading into winter.
• Cut away yellow, brown, or dying foliage so it does not fall into the water and decay over winter.
• A clean fall cutback along a visible pond edge reads as intentional upkeep instead of an overgrown corner, which helps if you are in a neighborhood with an HOA.

A tidy fall cutback around a pond edge or bog garden reads as intentional, cared-for landscaping and helps avoid a violation letter about an overgrown yard.

Winter

Memphis winters bring occasional hard freezes, so whorled marshpennywort needs help surviving if it is not rooted in deep water. Move it to deeper water or a frost-free spot until spring.

• If it is growing in a pond, move pots into water at least 20 inches deep. That extra depth insulates the roots even if the surface ices over.
• If it is in a shallow container or small water feature, bring it into an unheated garage or basement that stays above freezing.
• Do not expect new growth or feed it during winter. It is normal for it to sit dormant until temperatures rise again in spring.
• Memphis's coldest stretch usually lands in January, so watch for hard freeze warnings and move plants ahead of a deep freeze, not after.

Keeping the dormant plant contained over winter, in a garage or deep water instead of a bare pot sitting on the pond edge, reads as intentional and helps avoid a violation letter about winter yard clutter.

Spring

Spring is when whorled marshpennywort wakes back up in Memphis. Once the average last frost passes in late March, it is the best time to divide crowded clumps and get new plants settled.

• Memphis's average last spring frost is around March 30, so hold off moving containers back outside or restarting an outdoor pond setup until after that.
• Divide crowded clumps and replant the extra pieces. Since it spreads by runners, division is an easy way to make more plants for other wet spots in the yard.
• Start light feeding again once new growth shows up, after holding off over winter.
• Check that water depth is still around one to four inches. Spring rain in the Memphis area can also raise pond levels, so make sure runners are not washed loose.

Summer

Summer is peak growing season for whorled marshpennywort in Memphis's heat and humidity. Keep the water level steady and expect fast growth that needs regular trimming.

• Keep it in standing water or consistently wet soil through Memphis's hot, dry stretches. As a wetland plant, it will decline quickly if it dries out.
• It blooms with small white flowers from spring into early fall, though the flowers are easy to miss under the round leaves.
• Trim back runners every few weeks in summer so it does not crowd out other pond plants or cover the whole water surface.
• If algae or duckweed start competing for space in a full sun spot, a little afternoon shade can help it hold its own.