Arctous

Illustrator: Yevonn Wilson-Ramsey

Copyright: Flora of North America Association

Shrubs, not burled; bark brownish, exfoliating in papery sheets from older stems. Stems prostrate, extensively branched, glabrous. Leaves deciduous (leaf or leaf bases marcescent), bifacial; blade ovate or obovate to oblanceolate, subcoriaceous, margins crenate-serrate, ± plane, surfaces glabrous (margins ciliate toward base). Inflorescences racemes (formed on current year’s growth), 2–7-flowered; bracteoles absent. Flowers bisexual; sepals persistent, 5, distinct, broadly ovate; petals 5, connate nearly their entire lengths, white, cream, yellow, or green, corolla urceolate; stamens 10, included; filaments dilated, (usually hairy at base); anthers (reddish), with 2 (recurved), dorsal awns, dehiscent by 2 terminal pores; ovary 4–10-locular; stigma capitate. Drupes black-purple, brick red, or scarlet, globose, juicy, smooth; pyrenes 4–5, distinct. Seeds 4–5, distinct, (ovoid), not angled; (testa bony). x = 13.

Distribution

North America, Europe, Asia.

Discussion

Species 3 or 4 (2 in the flora).

The genus Arctous differs vegetatively from Arctostaphylos in having leaves with winged petioles and crenate to serrulate margins, fruits that are bright red or black and juicy (in Arctostaphylos the fruits are mealy or granular), and only five nutlets with hard, smooth endocarps (in contrast to Arctostaphylos, where the fruits have ten sculptured nutlets). Arctous has flowering buds that develop in the spring, as opposed to Arctostaphylos, in which buds form in the summer and autumn and lie dormant during the winter. Phylogenetic studies employing molecular methods place Arctous as the sister group to Arctostaphylos. Both species of Arctous in the flora area turn bright orange-red in autumn and are suitable for the alpine or rock garden.

Selected References

None.

Lower Taxa

Arctous alpina, Arctous rubra

Key

1	Leaf blades 4-15 mm, surfaces rugose, hairy toward base and on petiole (hairs 1-2 mm); twigs clothed with persistent old leaves or petioles; corolla lobes 0.5 mm; fruits black- purple; stones 2.7-4.6 × 2-3.6 mm.	Arctous alpina
1	Leaf blades (10-)15-30(-60) mm, surfaces not or only slightly rugose, glabrous; twigs bare of old leaves; corolla lobes 1 mm; fruits brick red or scarlet; stones 2.5-3 × 1.6-2.2 mm.	Arctous rubra