Juniperus horizontalis

Juniperus horizontalis, the creeping juniper or creeping cedar,[3] is a low-growing shrubby juniper native to northern North America, throughout most of Canada from Yukon east to Newfoundland, and in the United States in Alaska, and locally from Montana east to Maine, reaching its furthest south in Wyoming and northern Illinois.

Juniperus horizontalis
Foliage and cones
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressaceae
Genus: Juniperus
Species:
J. horizontalis
Binomial name
Juniperus horizontalis
Moench 1794
Natural range of Juniperus horizontalis
Synonyms[2]
  • Juniperus prostrata Pers. 1807
  • Juniperus repens Nutt. 1818
  • Juniperus racemosa Risso 1826
  • Juniperus hudsonica Forbes 1839
  • Sabina prostrata (Pers.) Antoine 1857
  • Sabina racemosa (Risso) Antoine 1857
  • Sabina horizontalis (Moench) Rydb. 1912

It lives up to both its scientific and common names, reaching only 10–30 cm tall but often spreading several metres wide. The shoots are slender, 0.7–1.2 millimetres (0.028–0.047 in) diameter. The leaves are arranged in opposite decussate pairs, or occasionally in whorls of three; the adult leaf blades are scale-like, 1–2 mm long (to 8 mm on lead shoots) and 1–1.5 millimetres (0.039–0.059 in) broad, and derive from an adnate petiole. The juvenile leaves (on young seedlings only) are needle-like, 5–10 mm long. The cones are berry-like, globose to bilobed, 5–7 millimetres (0.20–0.28 in) in diameter, dark blue with a pale blue-white waxy bloom, and contain two seeds (rarely one or three); they usually have a curved stem and are mature in about 18 months. The male cones are 2–4 millimetres (0.079–0.157 in) long, and shed their pollen in early spring. It is dioecious, producing cones of only one sex on each plant.

It is closely related to Juniperus virginiana, and often hybridizes with it where their ranges meet in southern Canada. Hybrids with Juniperus scopulorum also occur.

Cultivation and uses

Well over 100 different cultivars have been selected for use as ornamental plants in gardens, their strictly prostrate growth habit being valued for ground cover. Popular examples include 'Bar Harbor', 'Blue Acres', 'Emerald Spreader', 'Green Acres', and 'Wiltonii' ("Blue Rug Juniper"). Many of the most popular cultivars have strikingly glaucous foliage, while others are bright green, yellowish or variegated.

  • Plant at Pancake Bay sand dunes, Ontario, Canada
  • Juniperus horizontalis 'Wiltonii' as a garden plant

References
  1. Farjon, A. (2013). "Juniperus horizontalis". IUCN Red List of Threatened Species. 2013: e.T42237A2965318. doi:10.2305/IUCN.UK.2013-1.RLTS.T42237A2965318.en.
  2. Juniperus horizontalis The Plant List (2010). Version 1. Published on the Internet; http://www.theplantlist.org/ 22 Nov. 2011
  3. Bailey, L.H.; Bailey, E.Z.; the staff of the Liberty Hyde Bailey Hortorium. 1976. Hortus third: A concise dictionary of plants cultivated in the United States and Canada. Macmillan, New York.
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