Shrub
Desert Cassia
Senna artemisioides subsp. filifolia · Fabaceae
Also called: Shrubby Senna, Desert Senna, Feathery Cassia (related forms), Punty Bush
Desert Cassia (Senna artemisioides subsp. filifolia) is a very low-water shrub well suited to Tucson and the low desert. It grows to 4-6 ft H x 4-6 ft W in full sun, with a moderate to fast growth rate.
Desert Cassia at a glance
- Water use
- Very Low (established)
- Sun
- Full sun; tolerates reflected heat.
- Mature size
- 4-6 ft H x 4-6 ft W
- Growth rate
- Moderate to fast
- Bloom
- Bright yellow (small five-petaled flowers in clusters), Late winter through spring (peak roughly January-April), with occasional sporadic rebloom.
- Cold hardiness
- Hardy to about 15-20 F (USDA zones 8-11); generally root-hardy and recovers from light frost damage.
- Soil
- Adapted to poor, rocky, alkaline desert soils; requires excellent drainage. As a legume it fixes nitrogen and needs little soil fertility.
- Native range
- Native to arid and semi-arid inland Australia; widely cultivated and well adapted in the Sonoran Desert low desert. (Senna nemophila and Cassia nemophila are outdated synonyms for this taxon.)
- Best used as
- Mass planting, Informal hedge or screen, Foundation and filler shrub, Color accent in winter/spring, Median and parking-lot xeric plantings
- Wildlife
- Yellow flowers attract bees and butterflies; seeds eaten by some birds.
- Toxicity
- Senna species contain compounds that can be mildly toxic/purgative if ingested in quantity; seeds and foliage are best considered low-risk but not for consumption by people or livestock.
How to grow Desert Cassia in Tucson & the low desert
Watering
Very drought tolerant once established; deep-water every 2-4 weeks in summer, monthly or less in winter. Overwatering shortens its life and produces weak, floppy growth.
Fertilizer & nutrients
No fertilizer needed; as a nitrogen-fixing legume it thrives in lean native soil. Avoid high-nitrogen feeding, which promotes rank growth.
Pruning & care
Shear lightly right after spring bloom to remove spent flowers and seed pods and to maintain a compact mound; avoid hard pruning in heat. Light shaping keeps it dense; renewal-prune every few years.
Notes
Fine, thread-like (filiform) gray-green leaflets give a soft, airy texture. Tends to be relatively short-lived (often 8-12 years) and can look ragged if overwatered. Reseeds modestly. Frequently sold simply as 'desert cassia' or 'feathery senna.'
Sources: AMWUA / Water Use It Wisely (Cassias - Plant of the Month); Mountain States Wholesale Nursery (Senna nemophila / Desert Cassia); Green Things Nursery plant database; Plants of the World Online (Kew) for accepted nomenclature