Scientific: Lysiloma watsonii (formerly L. thornberi or Lysiloma microphylla var. thornberi)
Common: feather bush or fern-of-the-desert
Family: Fabaceae
Origin: Small riparian tree found SE of Tucson in Rincon Mountains and south into the mountain foothill washes of Sonora

Pronounciation: Lye-sil-LOO-ma wat-SONE-ee-i

Hardiness zones
Sunset
12-13
USDA 9-10 (arid regions only)

Landscape Use: Small multi-trunk residential shade tree casting light shade, xeric and oasis landscape design themes, flowering accent tree, background screen. Some list this as a poolside or patio tree; however, Lysiloma watsonii tends to be too messy for use around pools. Also, not for use in or around turf.

Form & Character: Graceful, lacy, large shrub or small multiple trunk tree if pruned as such, more upright when young to spreading with age

Growth Habit: Slow to moderate to 20 feet with greater spread, will produce root and trunk suckers profusely at its base

Foliage/texture: Pinnately compound foliage w/ 6-8 pairs of pinnae (secondary rachis) and 20 to 35 pairs of tiny leaflets per leaf that are each linear to oblong to 3/16 inch long, leaves turn golden yellow and fall off in Spring, but quickly replaced in Spring, stems have prominent lenticels, wood is somewhat brittle, fine texture

Flowers & fruits: Creamy white small 'puff-ball' flowers in terminal clusters in late Spring, ugly very hard bean pod fruit to 4-6" long in Summer, glaucous

Seasonal color: None of outstanding significance, although yellow foliage in April and cream flowers in May may be considered an accent by some

Temperature: Tolerant

Light: Full sun

Soil: Tolerant

Watering: Supplemental water encourages growth

Pruning: Feather bush wants to be a 'giant shrub on steroids', so care must be exercised to train it well as a multi-trunk tree. Forget about training it as a standard - that's not going to happen. In general, select three major scaffold branches for crown support and slowly raise the crown over time as the tree matures. Remove any branch suckers as necessary.

Propagation: Seed propagation is successful only if acid scarification is used on the hard seed coats (95% sulfuric acid for 30 minutes or until one sees a color change in the seed coat from dark to light).

Disease and pests: None

Additional comments: Feather bush is a nice small Arizona native multi-trunk tree (if trained properly) for urban landscapes. It's a versitle little tree that can be used in a myriad of situations. I do not recommend it's use as a lawn tree, though many do use it in this way. This tree will caste litter debris onto the ground throughout much of the year. Spent flowers can densely carpet the ground underneath this tree in May and June, and fruit pods will litter the landscape during the fall and early winter months. A deciduous habit in mid-spring also means leaf litter at that time of year. Feather bush will reseed in Phoenix landscapes near sources of water.