Senna mexicana var. chapmanii: Bahama Cassia, Bahama Senna, Chapman’s Sensitive Plant

This Florida-Friendly Landscaping™ publication is part of a series originally written by Edward F. Gilman. Visit https://ffl.ifas.ufl.edu/ to learn more about creating and maintaining attractive landscapes that protect Florida's water resources and environment.

Introduction

Chapman’s sensitive plant (Senna mexicana var. chapmanii) is an evergreen short-lived perennial shrub native to extreme south Florida, the Florida Keys, and parts of the Caribbean. This plant has an upright growth habit, and reaches a height of 2 to 4 feet, and spread of 3 to 6 feet (Figure 1). This plant has evergreen foliage, that is pinnately compound, with leaflets which have pointed tips (Figure 2). This species generally has 2 to 6 pairs of leaflets. This species is commonly confused with privet senna (Senna ligustrina), which is another closely related species also native to Florida; however, privet senna has linear to lanceolate shaped leaflets, 4 to 8 pairs of leaflets, and a larger growth form. This shrub produces small yellow showy flowers that are quite attractive next to the dark green compound leaves. Flowers are composed of five yellow petals, and seven stamens with red-orange anthers (Figure 3). This plant flowers throughout the year and produces slender seed pods that turn brown at maturity (Figure 4).

Chapman’s sensitive plant is relatively short-lived and may begin to decline after only four or five years. However, it often produces seedlings in the landscape. This plant is classified as being threatened in Florida. When sourcing this plant, be sure to purchase from a native plant nursery, or verify the species, as it is commonly confused with non-native Senna species, some of which are classified as High Invasion Risk in Florida (https://assessment.ifas.ufl.edu/assessments/senna-pendula-var-glabrata/).

Chapman’s sensitive plant is very attractive to pollinators, including butterflies, bumblebees, and other solitary bee species, and serves as the larval host plant for the cloudless sulfur (Phoebis sennae) and sleepy orange (Eurema nicippi) butterfly species. It is well-suited for use as a shrub or border planting, as a specimen, or in mass plantings.

General Information

Scientific name: Senna mexicana var. chapmanii

Previous name(s): Cassia bahamensis, Cassia chapmanii

Pronunciation: SEN-nuh mek-sic-KAHN-nuh variety chap-MAN-e

Common name(s): Chapman’s sensitive plant, Chapman’s wild sensitive plant, Bahama cassia, Bahama senna

Family: Fabaceae

Plant type: shrub

USDA hardiness zones: 10A through 11 (Figures 5 and 6)

Planting month for zones 10 and 11: year-round

Origin: native to Florida

Invasive potential: native plant that can often spread by seed into nearby landscapes

Uses: specimen; screen; border; mass planting; attracts butterflies; small parking lot islands (< 100 square feet in size); medium-sized parking lot islands (100–200 square feet in size); large parking lot islands (> 200 square feet in size)

Availability: grown in small quantities by a small number of nurseries

Description

Height: 2 to 4 feet

Spread: 3 to 6 feet

Plant habit: upright; round; sprawling

Plant density: moderate

Growth rate: moderate

Texture: fine

Use and Management

Chapman’s sensitive plant should be located in the landscape in a sunny to partially shaded location. This shrub prefers well-drained sandy soil, with alkaline pH. This plant is highly drought tolerant and tolerates nutrient poor conditions. Prune the plant back to the ground in the spring every few years to rejuvenate it. Chapman’s sensitive plant is not tolerant of freezing temperatures and should be protected from cold exposure. This plant may exhibit dormancy in drought or cold conditions.

Propagation is by cuttings or seed.

Design Considerations

With its low, mounding form and fine, airy texture, Chapman’s sensitive plant provides a splash of golden-yellow color to the front of the garden in fall and winter. Its primary function is to provide a mass of seasonal color and soft texture as a groundcover.

Use it in the foreground of mixed borders, as a foundation planting beneath windows, or massed as a sprawling groundcover to soften the edges of paths and patios. Give it room to achieve its 3-to-6-foot spread, allowing it to form natural drifts. To create layers, position it in front of taller backdrops like ornamental grasses.

For contrast, pair it with the airy plumes of Muhly grass (Muhlenbergia capillaris) behind it, the cool tones of blue porterweed (Stachytarpheta jamaicensis), or the bold, evergreen texture of coontie (Zamia integrifolia). Beyond its beauty, it also serves as a vital host plant for sulfur butterflies.

Pests and Diseases

No pests or diseases of major concern. As this species is a host plant, caterpillar damage to the foliage may occur but should not result in plant death.