Ailanthus altissimus (Mill.) Swingle



CC = *
CW = 5
MOC = 20

© SRTurner

Family - Simaroubaceae

Habit - Small to medium sized tree, to 20 m, incompletely dioecious, colonial from root suckers.

Stems - Trunks 1 or few, stout, the bark light grayish brown, initially relatively smooth, eventually developing thin, pale grooves and thin, darker ridges. Twigs stout, tan to reddish brown with numerous, slender, pale lenticels and large, prominent, more or less kidney-shaped leaf scars, the winter buds axillary (sometimes appearing asymmetrically terminal), depressed-globose, with several broadly rounded scales, densely short-hairy.

Leaves - Leaves 40-100 cm long, relatively short-petiolate. Leaf blades pinnately compound with 11-41 leaflets, these opposite, lanceolate, the lateral ones often somewhat curved toward the leaf tip, rounded to shallowly cordate and usually somewhat asymmetrical at the base, sharply pointed, the margins entire or with 1-3 pairs of blunt teeth toward the base, the surfaces short-hairy and also with scattered, minute glands, sometimes becoming nearly glabrous with age, the upper surface dark green, the undersurface pale or lighter green. One or more small, rounded projections often present on leaflet surface near base. Crushed leaves emit an unpleasant stench.

Ailanthus_altissimus_leaf1.jpg Leaf (partial), adaxial.

© SRTurner

Ailanthus_altissimus_leaf1a.jpg Leaflet adaxial surface.

© SRTurner

Ailanthus_altissimus_leaflet2a.jpg Leaflet abaxial. Note thickened nodule at margin.

© SRTurner

Ailanthus_altissimus_leaflet2.jpg Leaflet abaxial.

© SRTurner

Inflorescence - Terminal, large, diffusely branched panicles, lacking bracts, the numerous, individually stalked flowers solitary or in small clusters, each cluster subtended by a pair of minute, linear, reddish bracts that are shed before the flowers open.

Ailanthus_altissimus_inflorescence.jpg Staminate inflorescence.

© DETenaglia

Flowers - Mostly imperfect, but pistillate flowers sometimes appearing perfect due to presence of staminodes. Sepals 5, sometimes fused at base, triangular, spreading. Petals 5, to 4 mm long, alternating with sepals, somewhat concave, greenish, densely tomentose. Staminate flowers - Fetid. Stamens 10, erect to spreading. Filaments densely pubescent (at least in the basal 1/2), white, 2.5 mm long. Anthers yellow, 1.2 mm long. Pistillate flowers usually with 3-5 staminodes. Nectar disc present, irregularly lobed, dark purple to purplish brown. Ovary of 2-5 carpels, 2-5-locular. Style 1 per flower, with twisted, longitudinal lines equal to the carpel number, the stigma capitate and deeply 2-5-lobed.


© DETenaglia

Ailanthus_altissimus_flowers2.jpg Calyx.

© DETenaglia

Fruits - Schizocarps, appearing as small clusters of 2-5 samaras, these sessile, 3.0-5.5 cm long, 7-13 mm wide, narrowly oblong-elliptic, often somewhat spirally twisted toward the tip, usually strongly dark reddish-tinged at maturity, but becoming tan before dispersal. Seed 1 per samara, positioned near its midpoint, 5-8 mm long, ovate, strongly flattened, the seed coat fused to the samara wall.

Ailanthus_altissimus_fruits1.jpg Infructescence.

© SRTurner

Ailanthus_altissimus_fruits2.jpg Immature fruits.

© SRTurner

Ailanthus_altissimus_fruits.jpg Mature fruits.

© SRTurner

Flowering - May - June.

Habitat - Waste ground, along streams, base of bluffs, thickets, roadsides, railroads, commonly cultivated.

Origin - Native to Asia.

Lookalikes - Sumacs, especially Rhus glabra (smooth sumac).

Other info. - This common tree has been collected from scattered locations in Missouri but is probably far more common than collections indicate. It has been widely cultivated and is especially prevalent around urban areas. It grows rapidly and is resistant to disease and tolerant of air pollution. Although it mainly colonizes disturbed areas, in Missouri it has been known to badly invade forest margins. Once established it is difficult to control, and it should never be deliberately spread in the wild. The common name is extremely inappropriate, at least in Missouri.

Trees can be staminate, pistillate, or perfect. The staminate flowers and crushed foliage emit a disagreeable odor. The thickened nodules near the leaflet margins, particularly near the base of the leaflet, are a diagnostic character for identification.

A. altissimus has been used medicinally in the past. A tea made from the bark is used to treat diarrhea, dysentery, and tapeworms. Large doses of the tea, however, may be toxic. The tree has also been shown to have antimalarial properties. In China, some cases of hay fever have been attributed to the plant. The wood of this species can be mixed with other hardwoods for pulp in the paper-making process. Sap from the wood has been known to cause rashes in some people. Absorption of the sap through wounds may cause myocarditis.

Photographs taken at the Kansas City Zoo, 5-18-00 (DETenaglia); also along the Katy Trail in St. Charles County, 3-5-2012, and near Pacific, St. Louis County, MO, 7-23-2020 (SRTurner).