Senna marilandica (Maryland Senna) is an erect, herbaceous perennial boasting a handsome foliage of compound, medium to blue-green leaves adorned with 6-12 leaflets. They provide an excellent backdrop for the large clusters of beautiful bright yellow flowers in mid to late summer. Borne atop a stout central stem and in the leaf axils, they bloom for up to 3-4 weeks.
I. Appearance and Characteristics
Senna marilandica, commonly known as Maryland senna, Maryland wild senna, and wild senna, is a perennial flowering plant in the pea family (Fabaceae).
S. marilandica is native in the United States from Nebraska to the west, Florida and Texas to the south, Wisconsin to the north, and New York to the east. It is a species of special concern in Wisconsin. The plant is found in woodland edges, open fields, and thickets, and in moist areas such as riverbanks and moist prairies.
Senna marilandica has green, round, unbranched stems rising from a shallow, fibrous root system, reaching a height of about 2 m (6 ft). The compound leaves are alternate and pinnate with four to eight pairs of opposite leaflets on each leaf. Leaflets are up to 6 cm (2.5 in) long and 2 cm (0.75 in) wide and are ovate to elliptic in shape.
The inflorescences are racemes of six to nine yellow flowers, appearing both from the leaf axils (axillary) and at the end of the stems (terminal). The axillary inflorescences are up to 15 cm (6 in) long, and the terminal inflorescence is about 15–30 cm (6–12 in) long. Each flower is about 2 cm (0.75 in) across, with five yellow petals and five greenish yellow sepals. The stamens have prominent brownish anthers. The flowers do not have nectaries. After the flowers are fertilized, drooping pea-like seed pods, up to 8 cm (3 in) long, appear.
The foliage of maryland senna(Senna marilandica) gives off a malodorous scent when it’s ground up. Because of the unpleasant taste, this species is usually ignored by deer.
The flowers bloom from early July through late August, and the seed pods form from early August through late September. Bumblebees, butterflies, and solitary bees visit the flowers. Although the flowers do not have nectaries, extrafloral nectaries are located at the base of the leaves that are higher on the stem, in the inflorescence, and ants, parasitic wasps, and lady beetles feed on the nectar.
Unlike many members of the pea family, S. marilandica is not nodulated by nitrogen-fixing bacteria.
S. marilandica is a larval host to the cloudless sulphur (Phoebis sennae), orange-barred sulphur (Phoebis philea), sleepy orange (Eurema nicippe), and little sulphur (Eurema lisa) butterflies.
II. How to Grow and Care
Maryland senna is recognized for its adaptability and low maintenance requirements, making it suitable for a variety of garden settings. The plant thrives in full sun to partial shade and prefers well-drained soil. A special care point for maryland senna is its tolerance for drought, which eliminates the need for frequent watering once established.
Sunlight and Soil
Performs best in full sun in rich, medium moisture, sandy or clay, well-drained soils.
Watering
Maryland senna thrives in conditions that mimic its native environment, which includes periodic dry spells followed by substantial rainfall. This species is drought-tolerant and has adapted to efficiently utilize water when it’s available. For optimal growth, maryland senna should be watered once every two weeks, allowing the soil to dry out between watering sessions. Typically grown outdoors due to its resilience and adaptability, maryland senna benefits from a well-draining soil composition that prevents waterlogging, crucial for maintaining healthy roots during wetter seasons.
Fertilizing
For maryland senna, optimal flourishing requires balanced nutrition fertilizers (N-P-K in equal parts, e.g., 10-10-10) to maintain robust growth, and high phosphorus fertilizers to bolster flowering. Fertilize sparingly in spring at the onset of new growth, and again mid-summer if growth seems sluggish. A modest amount, following label instructions, prevents nutrient overload. Fertilization demands oscillate with growth stages; younger plants benefit from more frequent feeding.
Use slow-release formulas to minimize runoff and environmental impact. Always water thoroughly after application to aid in nutrient absorption. A practical tip: observe maryland senna’s response to feeding and adjust practices accordingly.
Pruning
Pruning is generally not necessary, but can be done to maintain the desired shape and size or to remove any damaged foliage.
Propagation
Maryland senna is effectively propagated through sowing. To maximize success, it is advisable to use fresh seeds which should be sown in a well-draining soil mix. Prior to sowing, an overnight soak in warm water can enhance germination rates by softening the seed coat. Sow the seeds at a shallow depth and keep the soil moist but not waterlogged. Consistent warmth and light will assist in germination, so a sunny spot is ideal for maryland senna.
Transplanting
The best time to transplant maryland senna is between S1 and S2, as this promotes robust growth. Choose a well-drained position bathed in full or partial sunlight for maryland senna to thrive. Remember, keeping the rootball intact during transplantation ensures a smooth shift for the plant.
Pests and Diseases
No serious pest or disease problems.
III. Uses and Benefits
Maryland senna is very useful and adaptable in the garden, this is a fine choice for mixed borders, cottage gardens, wild gardens, prairies and meadows, and naturalized areas.