Juniperus horizontalis

Shrubs dioecious, prostrate to decumbent; crown depressed. Bark brown, exfoliating in thin strips, that of small branchlets (5–10 mm diam.) smooth, that of larger branchlets exfoliating in wide strips or plates. Branches creeping; branchlets erect, 3–4-sided in cross section, ca. 2/3 or less as wide as length of scalelike leaves. Leaves green but turning reddish purple in winter, abaxial gland elliptic, conspicuous, exudate absent, margins entire (at 20× and 40×); whip leaves 4–8 mm, not glaucous adaxially; scalelike leaves 1.5–2 mm, mostly overlapping to 1/3 their length, apex rounded or obtuse to acute and apiculate, spreading. Seed cones mostly maturing in 2 years, of 2 distinct sizes, generally with curved peduncles, globose to ovoid, 5–7 mm, blue-black to brownish blue when mature, lightly glaucous, soft and resinous, with 1–2(–3) seeds. Seeds 4–5 mm. 2n = 22.

Habitat: Sand dunes, sandy and gravelly soils, prairies, slopes, rock outcrops, and stream banks
Elevation: 0–1000 m

St. Pierre and Miquelon, Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon, Alaska, Ill., Iowa, Maine, Mass., Mich., Minn., Mont., Nebr., N.H., N.Y., N.Dak., S.Dak., Vt., Wis., Wyo.

Discussion

Juniperus horizontalis, a prostrate species, hybridizes with the trees J. virginiana and J. scopulorum (R. P. Adams 1983; N. C. Fassett 1945; M. Palma-Otal et al. 1983) and is closely related to both. The hybrid between J. horizontalis and J. scopulorum has been named J. × fassettii Boivin.

Selected References

None.

Lower Taxa