Knife leaf Wattle

Evergreen shrub or small tree to 5 m tall, with stiff, prickle-tipped leaves. leaf Appearing simple, rounded-triangular, somewhat twisted, and oriented vertically on the branch; blade to 2.5 cm long. flower Yellow, many in dense globose heads about 1 cm diam., 5–15 heads clustered in a raceme; stamens showy. Mar.–May.

HABITAT / RANGE Introduced from e. Australia; commonly planted in Calif., occasionally escaping, 50–300 m.

Silver Wattle Acacia dealbata Link - The bluish-green bipinnately compound leaves with 20–42 primary segments, and 40–130 leaflets per segment, distinguish this species Evergreen unarmed tree, 6–15 m tall, with feathery bluish-green foliage. The spreading branches form a bluntly conical or rounded crown. Trunk erect, 1 to few, 10–30 cm diam. bark Young bark smooth and gray; older bark hard, brownish-black, shallowly fissured. twig Minutely angled, grayish-pubescent. leaf Alternate, bipinnately compound, blade 7–16 cm long, nearly as wide, petiole short. 

Primary segments 20–42, overlapping, raised glands present on the rachis between, or immediately below, pairs of primary segments; leaflets 40–130 per segment, each 2–3.5 mm long, oblong, crowded and touching, thin and flexible, bluish-green, minutely glandular. flower Bright yellow, about 13–42 in globose heads 6–7 mm diam., borne in axillary or terminal sprays of racemes. Feb.–Apr. fruit Legume straight or constricted between the seeds, flat, often slightly contorted, 3–8 cm long, 7–13 mm broad, papery or leathery, hairless, at first silvery blue, becoming reddish-brown or blackish, spreading or hanging, dehiscent.

HABITAT /RANGE Introduced from se. Australia; cultivated in sw. Ore. and c. and s. Calif., occasionally escaping, roadsides and disturbed areas, 0–500 m.

Similar Species - Cootamundra Wattle has fewer primary leaf segments and fewer leaflets. Green Wattle’s leaves are olive green and its twigs are winged. Black Wattle has olive-green leaves, angled twigs, and glands between primary segments and also along the rachis.

Notes Silver Wattle is commonly planted as a fast-growing ornamental, but it suckers aggressively, diminishing its desirability as a street tree. In some parts of the world where it has been introduced, it has become invasive. Its pollen is highly allergenic to some individuals.

Green Wattle “Acacia decurrens Willd”. Evergreen unarmed shrub or spreading tree to 15 m tall, easily confused with Silver Wattle. Twig Hairless, bearing raised wing-like ridges. Leaf Bipinnate, olive green, with 6–26 primary segments, and 40–80 well-separated linear leaflets per segment; glands on rachis not obvious. Flower Feb.–Apr.

HABITAT /RANGE Introduced from se. Australia; cultivated and escaping, mostly near the coast in Calif. in disturbed urban areas, 0–100 m.