Hardiness zones:
Sunset 8, 9, 12-24
USDA 9 - 11
Landscape Use: Silhouette tree, street tree, great tree for narrow spaces if form is upright
Form & Character: Evergreen tree, strongly vertical, weeping, open, airy, variable in shape from strongly upright to spreading, glaucous
Growth Habit: Vigorous, upright when young to spreading with age, to 40'. Long, narrow young stems and branches are pendulous often crossing over other branches and growing back into the canopy
Foliage/texture: Gray 16" long linear phyllodes (modified petioles that look like and function like leaves) contrast well with maroon colored twigs and young stems, trunk smooth when young changing to roughened dark gray to brown age, fine texture
Flowers & fruits: 1/2" small, cream-yellow puff-ball flowers originate from axillary meristems in November to January; fruit a long "chain" pod to 8", constricted between seeds
Seasonal color: Flowers (only somewhat ornate) in late fall and winter.
Temperature: Very tolerant of lower desert heat
Light: Full sun
Soil: Well-drained soils are best
Watering: Deep water established trees about once per month during summer, otherwise little to no water needed.
Pruning: Stake rigorously when young. Prune regularly when young to establish scaffold branch system and elevate the canopy base
Propagation: From scarified (95% sulfuric acid best) seed, cuttings or transplanted root suckers. Seedling plants are variable in shape in form
Disease and pests: Can succumb to Texas root rot if soil is heavy and/or poorly drained soil
Additional comments: This is truly an excellent upright tree for light shade and silhouette effects. It takes intense desert heat and drought well, but needs aggressive training when young to establish structural integrity and aesthetic branch architecture. It will reseed in the irrigated urban landscapes of Phoenix and will shed relatively moderate amounts of phyllode and fruit pod litter, but it is not locally invasive. 100 miles south of Phoenix in the pueblo city of Tucson (slightly higher elvation and cooler desert climate - Sunset zone 12), shoestring acacia shows a tendency to more aggressively reseed and is considered by some to be invasive in and around the Tucson area. Shoestring acacia roots assist Rhizobium bacteria in fixing soil N2. It also has a beautiful wood grain and heartwood of high quality that is very hard and close-grained. The wood will take fine polish and useful for furniture.
