Shrub
Feathery cassia
Senna artemisioides · Fabaceae
Also called: Feathery senna, Silver cassia, Wormwood senna, Cassia artemisioides (synonym)
Feathery cassia (Senna artemisioides) is a low-water shrub well suited to Tucson and the low desert. It thrives in full sun, with a moderate to fast growth rate.
Feathery cassia at a glance
- Water use
- Low (established)
- Sun
- Full sun; tolerates reflected heat. Best bloom and form in full sun.
- Mature size
- 3-6 ft H x 4-6 ft W (can reach larger if heavily watered)
- Growth rate
- Moderate to fast
- Bloom
- Bright yellow, fragrant, five-petaled flowers covering the plant, Mid/late winter into early spring (roughly January-April), heaviest in late winter.
- Cold hardiness
- Hardy to about 15-20 F; roughly USDA zones 9-11. Evergreen.
- Soil
- Needs well-drained soil; sandy or gravelly desert soils are ideal. Intolerant of waterlogged or poorly drained sites.
- Native range
- Native to arid inland Australia; not native to the Sonoran Desert. Widely used and well-adapted in low-desert Southwest landscapes.
- Best used as
- Winter-into-spring yellow color, Informal screen, hedge, or massing, Foundation and background shrub, Pollinator (bee) garden, Low-water residential and commercial landscapes
- Wildlife
- Flowers attract bees, butterflies, and other pollinators. Larval host for some sulphur butterflies (Senna/Cassia feeders).
- Toxicity
- Many Senna species contain mildly toxic compounds; seeds/pods are best considered not for ingestion and can be mildly toxic to pets if eaten in quantity. Generally low landscape concern.
How to grow Feathery cassia in Tucson & the low desert
Watering
Drought tolerant once established; deep-water infrequently (roughly every 2-4 weeks in summer, less in winter). Overwatering causes rank, leggy, overgrown growth and shortens life. Deep, infrequent irrigation keeps it dense.
Fertilizer & nutrients
None needed; as a nitrogen-fixing legume it does not require fertilizer and performs best in lean soil without it.
Pruning & care
Prune/shear ONLY right after flowering (late spring, roughly April-May), partly to remove the unattractive seed pods. Flower buds set in late summer for the following winter, so pruning in summer/fall sacrifices the next bloom. Avoid hard shearing into bare wood.
Notes
Often still sold as Cassia artemisioides; the accepted name is Senna artemisioides. Soft, fine, gray-green needle-like foliage with a clean evergreen look year-round and a heavy late-winter bloom. Key care points: keep it on the dry side and prune only after flowering to preserve next year's flower buds and remove seed pods. Can self-seed where overwatered.
Sources: AMWUA / Water Use It Wisely 'Plant of the Month: Cassias'; Arizona State University (Mary Irish / W. Feldman) desert landscape plant references; University of Arizona Cooperative Extension; San Marcos Growers (Senna artemisioides)