BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Spiraea betulifolia | White Spirea 



GENERAL BOTANICAL CHARACTERISTICS : 
White spirea is a native, moderately shade-tolerant, deciduous,
rhizomatous shrub, with root development well into the soil profile
[2,9,14,19,35,37].  White spirea has cinnamon-brown scaly bark on its
erect stems, which are 1 to 3 feet (30-90 cm) tall [40].  The small
flowers are gathered in nearly flat-topped clusters about 1.5 inches (4
cm) across.  The flowers turn brown soon after fertilization and give
way to small, dry, podlike fruits [32].


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Cryptophyte (geophyte)
   Undisturbed State:  Phanerophyte (nanophanerophyte)
   Burned or Clipped State:  Cryptophyte (geophyte)


REGENERATION PROCESSES : 
White spirea is rhizomatous and usually grows in extensive colonies
[2,14,19,35].  Mechanical or natural disturbances rarely destroy the
white spirea root system, which usually will resprout within the next
growing season.  

White spirea stems often show signs of woody swellings due to the
fusion of adjacent segments.  Incipient perennating buds are well
distributed along the entire length of the rhizome [2].  Any section of
the rhizome is probably capable of generating new stems if it is large
enough to provide the carbohydrates necessary for sprouting.  White
spirea also appears capable of some layering from aerial stems.
Bradley [2] found a high proportion of white spirea perennating tissues
residing in the mineral soil at an average depth of 4.4 inches (11.2
cm).

White spirea produces small seeds that are occasionally dispersed via
small birds, rodents, and strong winds.  Overall seed production and
dispersal is low.  A soil seed-bank sampling study found white spirea
to be the least represented shrub species [25].  Seedlings of white
spirea are rarely found [35].


SITE CHARACTERISTICS : 
White spirea is common on brushy or open slopes, as well as in forests
from the foothills through the montane zone.  It is often abundant in
low-elevation (1,000 to 4,000 feet [305-1,219 m]) dry forests, but can
also be found in some high-elevation (10,000 feet [3,048 m]) wet forests
[19,23,32].  White spirea grows well on dry, rocky sites because of its
rhizomatous nature [15,32].  Soil moisture does not play a major role in
the distribution and phenology of white spirea [14].  White spirea
occupies forest habitat types associated with parent material ranging
from limestone to quartz [6,28].  Aspect had a major influence on the
survival of transplanted white spirea in northwestern Montana [21].
Survival was significantly lower on western aspects than on either
southern or eastern aspects.


SUCCESSIONAL STATUS : 
White spirea appears to be a satisfactory indicator plant for varying
climatic conditions [14].  Descriptions of northern and central Idaho
habitat types indicate that white spirea increased in importance as an
indicator species in the slightly drier and warmer conditions found in
ponderosa pine and Douglas-fir habitat types.

White spirea's canopy cover declines gradually beneath a tree
overstory, making it an indicator of late-seral to climax conditions.
In drier portions of Douglas-fir/ninebark (Physocarpus malvaceus)
habitat communities, which often border Douglas-fir/white spirea types,
white spirea may persist as a climax component of the shrub layer.  In
much of the Douglas-fir/ninebark habitat type, however, white spirea
gradually gives way to ninebark, making it a late seral indicator [35].


SEASONAL DEVELOPMENT : 
Seasonal development of white spirea is closely related to temperature
[14].  In eastern Washington, white spirea developed up to 2 months
later at higher elevations than at lower elevations [14].  Bud break
generally occurs in April, and first bloom occurs anywhere from May to
July.  Phenological development was drastically retarded for
transplanted white spirea (first bloom and seed production) in eastern
Washington [14].  Seasonal progression of white spirea phenology does
not relate well to calendar dates or photoperiodic tables, due to the
temperature differences between elevational sites.

Approximate timing of phenological events for white spirea at different
elevations on the Entiat Experimental Forest, eastern Washington, from
1972 to 1973 were as follows [14]:


Phenological Phase                  Elevation

                          590 m       1105 m        1635 m
                        (1,935 ft)   (3,624 ft)    (5,363 ft)

Bud Break              late March   early April  late April
4-6 leaf development   early April  mid-April    early May
Floral initiation      early May    mid-May      May-June
First bloom            May-June     mid-June     July
Peak bloom             mid-June     early July   July

Related categories for Species: Spiraea betulifolia | White Spirea