BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Juniperus horizontalis | Creeping Juniper 



GENERAL BOTANICAL CHARACTERISTICS : 
Creeping juniper is a slow-growing, native, prostrate, mat-forming shrub
[5,20].  Creeping juniper usually grows to less than 8 to 12 inches (20-
30 cm); mats can grow up to 23 feet (7 m) across [23,26].  Plants which
are somewhat taller may occur in some locations where browsing inhibits
peripheral spread or where disease promotes abnormal growth [28].  Stems
of creeping juniper may be decumbent, procumbent, or prostrate [39].
The trailing stems are capable of rooting at nodes, producing
adventitious roots at irregular clusters [5,36].

Older branches are dark reddish brown to gray, whereas younger twigs are
reddish brown to yellow [20].  The bark is reddish brown and exfoliates
into thin flakes or strips [36].  Creeping juniper varies in color and
morphology.  Plants range from a bright green to dark green, yellow
green, or glaucous [13,20].  Leaves are opposite and scalelike at
maturity but more acicular when young [13,36].

Staminate cones are pale brown or yellowish, ripening to purple, and
cylindrical to ellipsoid [20,28].  Cones or fruits are globose and
green, ripening to a glaucous, bluish purple or bluish black [36,39].
The berrylike fruits are succulent and contain two to six reddish-brown,
ovoid to round seeds [20,23,28,36,39].


RAUNKIAER LIFE FORM : 
   Phanerophyte
   Chamaephyte
   Hemicryptotphyte


REGENERATION PROCESSES : 
Evidence suggests that creeping juniper rarely reproduces by seed [28].
It can readily root along horizontally spreading branches or leaders
[28].  The majority of new plants are formed by the breakup of older
shrubs [28].

Creeping juniper is dioecious [36] and produces berries which mature in
either 1 or 2 years [20,23,39].  Stephens [36] reported that cones are
fertilized in the spring of one season and reach maturity by the fall of
the following growing season.

Germination of creeping juniper seeds is poor.  Miller [28] reported
that only nine of approximately 9,500 new and 2-year-old seeds
germinated.  The seeds of most species of juniper must undergo a
distinct period of rest and afterripening [30].  Juniper seeds which
have not undergone afterripening generally exhibit very low germination
rates (approximately 1%) [30].  Juniper seeds are semipermeable with a
thick seedcoat [30].  Most juniper seeds are apparently resistant to
damage, and germination may actually be enhanced by disgestive processes
[3,10].  Many small mammals, birds, and deer consume creeping juniper
seeds and serve as dispersal agents [28].


SITE CHARACTERISTICS : 
Creeping juniper occurs on open prairies; dry, rocky hillsides; mountain
foothills; open woods; rock ledges or escarpments; dry montane ridges
and hilltops; and in wash areas [20,23].  This species is capable of
growing on dry, harsh, eroded sites or exposed pavement [28,36,37,42].

Creeping juniper commonly grows on thin, poorly developed rocky soils
[28].  It occurs on sand, bare rock, alluvium, clay loam or slightly
basic soils often low in organics [5,36,42].  Growth by soil type is as
follows [9]:

        gravel:  poor           organic:  poor
        sand:  fair             acidic:  fair-poor
        sandy loam:  good       saline:  good-poor
        loam:  good             sodic:  poor
        clay loam:  good        sodic-saline:  poor        
        clay:  fair
        dense clay:  poor
        
Creeping juniper commonly grows as an understory species with ponderosa
pine (Pinus ponderosa), limber pine, or Douglas-fir (Pseudotsuga
menziesia) [28].  Other plant associates include blue grama (Bouteloua
gracilis), western wheatgrass (Pascopyrum smithii), needle-and-thread
(Stipa comata), green needlegrass (S. viridula), prairie sandreed
(Calamovilfa longifolia), rough fescue, Idaho fescue (Festuca
idahoensis), shrubby cinquefoil (Potentilla fruticosa), silver
sagebrush, dotted gayfeather (Liatris punctata), and little bluestem
[28,34,41,42].

Growth occurs on a number of topographic positions including the summits
of ridges and on east- or north-facing slopes in the Dakota Badlands
[6,32].  Elevational ranges are as follows [9]:

        from:  3,700 to 3,700 feet (1,128-1,128 m) in CO
               4,300 to 8,000 feet (1,311-2,438 m) in MT
               5,200 to 7,000 feet (1,585-2,134 m) in WY


SUCCESSIONAL STATUS : 
Creeping juniper is climax dominant or indicator in a number of habitat
type classification schemes [24].  Its ability to survive on dry, rocky
sites enables it to become part of the topoedaphic climax vegetation in
portions of Montana and the Dakotas [21].  Creeping juniper is
relatively common in climax riverbreak vegetation of the Great Plains
[28].


SEASONAL DEVELOPMENT : 
Creeping juniper begins annual growth in early April when the plants
"green up" [28].  The complete process of seed formation and maturation
takes 2 years.  Strobiles typically mature and open in early April or
May [28,36].  Cones are usually fertilized during the spring of one
season and mature by August or September of the following year [36].
General phenological development is as follows [28]:

            Date                           Phenological stage
     ------------------              ------------------------------
     April 22 to May 7               pollen shed
        June 23                      new staminate cones
        June 25                      first berry formation
        mid-July                     last berry formation
        mid- to late July            curved penunclate twigs
                                     characteristic of new pistillate
                                     buds begin to form
        mid-November                 all "berries" had turned purple

Flowering dates for creeping juniper vary somewhat according to
geographic location, but flowering usually occurs during May or June
[20,23].

Fruit production peaks in late June to early July.  Ripe fruit remains
on the plants for 1 or 2 years [28].  In Montana, annual vegetative
growth is completed by September or early October [28].

Related categories for Species: Juniperus horizontalis | Creeping Juniper