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Robert H. Mohlenbrock. USDA SCS. 1989. Midwest wetland flora: Field office illustrated guide to plant species. Midwest National Technical Center, Lincoln. Provided by USDA NRCS Wetland Science Institute (WSI)., no rights reserved (CC0) · Wikimedia Commons

Senna, Genus, marilandica, Species,

Genus & species

maryland senna

Fabaceae Eastern and central United States

Attracts Pollinators Attracts Butterflies Deer Resistant

SunFull Sun – Part Shade

WaterMedium

HardinessZones 4–8

Overview

Senna marilandica is a clump-forming herbaceous perennial of the eastern and central United States, growing 3–6 feet (0.9–1.8 m) tall on stout, upright stems. The pinnately compound leaves are 6–8 inches (15–20 cm) long with four to eight pairs of oval leaflets and a small club-shaped gland near the base of the leaf stalk. Clusters of yellow flowers about 0.75 inch (2 cm) across, each with five petals and dark-tipped anthers, open from July to August in the upper leaf axils. Flat, slightly curved pods 2.5–4 inches (6–10 cm) long follow, turning black and persisting into winter. S. marilandica grows in moist open woods, prairies, stream banks, and roadsides from Pennsylvania and Iowa south to Texas and Florida. The leaves carry nectar glands that draw ants, and the foliage is a larval food for sulphur butterflies. All parts contain anthraquinone compounds that act as a strong laxative if eaten. The plant spreads slowly by rhizomes and self-seeds, and the tall stems can lean in rich soil or shade.

Native Range

Senna marilandica is native to the eastern and central United States, from Pennsylvania and Iowa south to Texas and Florida. It grows in moist open woods, prairies, stream banks, floodplains, and roadsides.

Suggested Uses

Used in rain gardens, native meadows, pollinator plantings, and the back of moist borders. Spaced 24–36 inches (60–90 cm) apart, it supports bees and serves as a larval host for sulphur butterflies.

How to Identify

Identify S. marilandica by its 3–6 foot (0.9–1.8 m) stems, pinnately compound leaves of four to eight pairs of oval leaflets with a club-shaped gland near the leaf-stalk base, and clusters of yellow flowers with dark-tipped anthers in mid to late summer. Flat curved pods turn black as they ripen. The leaf-stalk gland and oval leaflets separate it from the pointed-leaflet Senna hebecarpa.

Appearance

Size & Dimensions

Height3' - 6'

Width/Spread2' - 3'

Colors

Flower Colors

yellow

Foliage Colors

green

Bloom Information

Bloom Period

~5 weeks

Flowers: July–August

Summer

Flowering occurs from July to August. Clusters of yellow flowers about 0.75 inch (2 cm) across, with five petals and dark anthers, open in the upper leaf axils and draw bees. Flat curved pods follow, turning black and holding through winter.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5 (Acidic to alkaline)

3579

Soil Types

clay loam silt

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Grow S. marilandica in full sun to part shade in moist, average to rich soil. It tolerates clay, seasonal wetness, and stream-side ground and suits rain gardens, meadows, and the back of borders. Soil pH from 5.5 to 7.5 is suitable. As a legume, it fixes nitrogen and grows on lean as well as fertile soil. In rich soil or shade the tall stems may lean and need support. It is hardy in USDA zones 4 through 8 and dies back to the ground each winter.

Pruning

Cut the dead stems to the ground in late winter before new growth emerges. Stems can be shortened by one-third in late spring to reduce height and limit leaning, which delays bloom slightly. The black pods can be left through winter or cleared to limit self-sowing.

Pruning Schedule

Prune: February–March

winter