Shrub · Sonoran native
Triangle-leaf bursage
Ambrosia deltoidea · Asteraceae
Also called: Triangleleaf bursage, Triangle bur ragweed, Rabbit bush
Triangle-leaf bursage (Ambrosia deltoidea) is a very low-water shrub native to the Sonoran Desert region well suited to Tucson and the low desert. It grows to 18-24 in H x 24-36 in W in full sun, with a slow to moderate growth rate.
Triangle-leaf bursage at a glance
- Water use
- Very Low (established)
- Sun
- Full sun; tolerates reflected heat
- Mature size
- 18-24 in H x 24-36 in W
- Growth rate
- Slow to moderate
- Bloom
- Inconspicuous yellowish-green (wind-pollinated), Late winter to spring (Feb-Apr), again with summer rains
- Cold hardiness
- Hardy to about 20-25 F; USDA zones 8-11
- Soil
- Well-drained native desert soils; tolerates rocky, gravelly, calcareous ground; poor fertility no problem
- Native range
- Sonoran Desert (Arizona Upland), Arizona and Sonora, Mexico; also Baja California
- Best used as
- Revegetation and restoration, Erosion control, Native/wildlife habitat gardens, Filler in desert landscapes, Nurse plant for cacti and trees
- Wildlife
- Key understory nurse plant of the Sonoran Desert, sheltering saguaro, paloverde, and ocotillo seedlings; provides cover and seed for small mammals, rabbits, and birds.
- Toxicity
- Not toxic to people or pets, but male flowers produce abundant wind-borne pollen that is a significant hay-fever allergen, and foliage can cause contact dermatitis in sensitive individuals.
How to grow Triangle-leaf bursage in Tucson & the low desert
Watering
Essentially no supplemental water once established; survives on rainfall. New transplants need occasional deep watering the first summer, then taper off completely.
Fertilizer & nutrients
None required; thrives in lean native soil and excess fertilizer or water causes leggy, weak growth.
Pruning & care
Little needed; lightly cut back in late winter/early spring to renew growth and remove frost-killed or dead stems. Avoid shearing.
Notes
A defining understory shrub of the Arizona Upland Sonoran Desert and the principal saguaro nurse plant. Drought-deciduous, dropping leaves and going dormant in dry spells. Best for naturalistic/native plantings rather than refined ornamental settings due to its allergenic pollen.
Sources: Arizona-Sonora Desert Museum (Ambrosia deltoidea plant care sheet); University of Arizona Cooperative Extension; Southwest Desert Flora; Mountain States Wholesale Nursery