BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cornus sericea | Red-Osier Dogwood 



GENERAL BOTANICAL CHARACTERISTICS : 
Red-osier dogwood is a deciduous, many-stemmed shrub which varies in
height from 3 to 19 feet (1-6 m) [60,142].  The young stems and twigs
are dark red, gradually fading to gray-green, and becoming red again in
the fall and winter [60,142].  The leaves are opposite with prominent
lateral veins that curve toward the tip and smooth edges [93].  Many,
small white flowers are borne in a flat-topped cyme and, unlike many
dogwoods, there are no large, showy bracts.  The flowers are followed by
berrylike fruits that are white or lead colored at maturity [126,143].

Red-osier dogwood's wide range and ability to tolerate extremely cold
temperatures (laboratory temperatures as low as -320 degrees F [-196
degrees C]) [96,126] have prompted a number of studies of its physiology
and cold acclimation [14,15,16,17,42,56,63,74,75,76,90,91,102,119,
120,139].  Red-osier dogwood avoids freezing injury caused by ice
forming within living protoplasm by having freezable water frozen
extracellularly [96].  The factors that seem to affect cold acclimation
the most are low temperatures, short days, water stress, and the
developmental stage of the plant [15,75,76,159].  Key points in the
developmental cycle, chilling requirements, and temperature effects have
been described and modeled [75,76,119,120,159].  Far red light,
characteristic of the long twilights at high latitudes, and short day
length promote cold acclimation [90].  Water-stressed plants have an
increased tolerance of freezing and increase their freezing point [16].
In plants exposed to short days, tissue changes occur that reduce the
plant's ability to take up water and simultaneously increase water loss
so that the plant partially dehydrates even when water is plentiful
[91,102].

A study of different geographic races found that stem pubescence and
leaf size and form vary, and plant form can vary from very upright to
decumbent between races, although there are no clear patterns [126].
Growth rates of more northern races are slower under shorter
photoperiods than those of southern races growing in their own
geographic areas.  Total growth of northern races was reduced because
they stopped growth and started cold acclimation earlier than more
southern races [126].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Natural regeneration of red-osier dogwood is both sexual and asexual
[60,126].  The flowers of red-osier dogwood are self-sterile and
outcrossing is obligate [34,47].  This is controlled by a single,
multiallelic gene that inhibits full pollen tube growth in the style of
the plant [62].  Pollinators include the honey bee, bumble bee, solitary
bee [47] and possibly beetles, flies, and butterflies [34].  Seeds are
dispersed primarily by songbirds, although other animals including
bears, mice, grouse, quail, partridges, and even ducks and cutthroat
trout may eat the fruit and disperse seeds [34,126,143].  The seeds may
be stored in seedbanks [117].  Individual plants generally first bear
fruit at 3 to 4 years of age, but older plants are more prolific [125].

Red-osier dogwood seeds have dormant embryos and need cold
stratification for 1 to 3 months [9,55,121].  Sometimes hard seed coats
are also present and scarification is then necessary [125].  Germination
rates increased after passage through a black bear's digestive tract
[115] but were inconsistant after passage through a pheasant's digestive
tract [80].  The seeds will remain viable in cold storage for 4 to 8
years [9].  Details of seed collection and nursery germination can be
found in several studies [9,80,121,144,148].

On good sites red-osier dogwood can form dense thickets through
vegetative reproduction [48,52].  Red-osier dogwood spreads by layering
when the lower stems touch or lie along the ground and root at the nodes
[48,60].  In the northeastern United States, production of new plants
from stolons is most likely for plants in very moist situations and wet
meadows [125].  Plants may also produce new shoots from the roots and
new branches from the bases of dying branches [125].  If 27 percent or
more of the stem is girdled by small rodents, the stem will die back to
the injury, and new growth begins below that point on the stem [104].
Red-osier dogwood resprouted promptly from the roots in riparian zones
in the airfall area and more slowly in the devastated zone following the
eruption of Mount St. Helens [92].


SITE CHARACTERISTICS : 
Red-osier dogwood is a characteristic species of swamps, low meadows,
and riparian zones; it is also found in forest openings, open forest
understories, and along forest margins [48,142].  It is a facultative
wetland plant [111].  It is found on warmer, more productive sites in
the taiga [141], in rich swamps [57], and generally on very rich, very
moist sites [66,116].

Red-osier dogwood's southern limits appear to be determined by high
temperatures [125].  Near its southern limit in New Mexico, it is only a
riparian species [27], and in other southwestern states and the southern
Great Plains, it is primarily a riparian species [46,70,85,143,147].  In
the Sacramento-San Joaquin Delta of California, it grows just above the
tidal zone and on hummocks and higher areas of marsh in oxbows and
overflow basins [21,151].  In bluestem (Andropogon spp.) prairie in
Minnesota, red-osier dogwood grows in sedge (Carex spp.) dominated
swales that are inundated during the spring [31].

Although red-osier dogwood grows on a variety of soils, it prefers rich,
moist soils [48,56,125,150].  Ratings in several western states give
growth on gravel as fair to poor; growth on sand, sandy-loam, and loam
as good; growth on clay-loam growth as fair to good; and growth on clay
or dense clay as poor [28].  Opinions differ on its pH preference which
is given as 5.5 to 7.5 [149] or 7.0 to 8.0 [138].  It needs high levels
of mineral nutrients for vigorous growth [57,149].  Growth on acidic
soils is rated as fair in Montana and Wyoming but poor in Colorado [28].
Growth on organic soils, saline soils, sodic soils, and sodic-saline
soils in Montana, Wyoming, and Colorado is rated as poor, and optimum
soil depth is given as over 20 inches (51 cm) [28].  Soil temperatures
can change root morphology and the mineral content of the stem and
leaves of red-osier dogwood [6].  The best root growth occurs at lower
soil temperatures than the best shoot growth [6].

Red-osier dogwood can tolerate flooding and, consequently, is found on
floodplains and wetlands and is often one of the first shrubs to invade
wet meadows [48,125,129].  Its seeds germinate above water level, but
after several years growth, the plants can live with the roots submerged
in water for most of the growing season [129].  Plants on such wet sites
are found in mineral rich swamps or fens and not in ombrotrophic,
sphagnum bogs [57].

Elevation:  Elevational ranges in several western states are as follows
[28,71,143]:

                            Minimum              Maximum
                         feet     meters      feet     meters
Arizona                  5,000     1,524      9,000     2,743
Colorado                 4,500     1,372     10,000     3,048
Montana                  3,400     1,036      6,600     2,012
Utah                     4,800     1,463      9,500     2,896
Wyoming                  5,500     1,676      8,300     2,530

Associates:  The plants most closely associated with red-osier dogwood
are willows and alders (Alnus spp.).  Other plants frequently found with
red-osier dogwood include cottonwoods, aspen (Populus tremuloides),
birch (Betula spp.), Wood's rose (Rosa woodsii), gooseberries (Ribes
spp.), hawthorne (Crataegus spp.), horsetails (Equisetum spp.), thistle
(Cirsium spp.), and Kentucky bluegrass (Poa pratensis).


SUCCESSIONAL STATUS : 
Red-osier dogwood is an early to mid seral species [11,140,148] that is
supressed in shade and is not normally found in the understory of closed
canopy forests [125].  It is found in the understory of mixed open
forests [48].  Red-osier dogwood needs moderate to full sunlight [11].
A shade-frame study found that red-osier dogwood grew best in 75 percent
of full light intensity.  Its natural occurrence in full sunlight may be
facilitated by its growth in wet situations where it encounters no water
stress [122].

Red-osier dogwood is a dominant understory shrub in the early
successional willow and balsam poplar (Populus balsamifera) communities
that follow oxbow lakes in Alberta, and it has 60 to 75 percent canopy
cover in these communities [140].  It is also the most important species
in the seral shrub-carrs of Wisconsin that succeed wet prairies, fens,
or sedge meadows and are followed by lowland forest or conifer swamp
[148].  Red-osier dogwood is not a primary invader in these areas.  It
enters the stand later in succession and is least common in greatly
disturbed stands [148].  Red-osier dogwood is also a successional
species in this area following fire or when a bog basin is partially
drained by stream downcutting [21].

In Ontario sugar maple-beech (Acer saccharum-Fagus grandifolia) and
eastern hemlock-yellow birch (Tsuga canadensis-Betula lutea) forests,
red-osier dogwood is a pioneer in open and disturbed areas [11].  In New
York wetland forest gaps caused by American elm (Ulmus americana)
mortality, red-osier dogwood is frequent and abundant in multiple-tree
gaps but rare beneath the closed canopy and in single-tree gaps [160].


SEASONAL DEVELOPMENT : 
One consequence of red-osier dogwood's wide geographic range has been
the development of geographic races with different seasonal responses.
A comparison of 21 clones from different areas grown together in a
Minnesota plot found that spring events, such as bud break, flowering,
and greening of the bark are, determined by temperature, and all of the
clones responded to the same temperature [126].  In contrast fall bud
set, red bark color, leaf abscission, and cold acclimation were
determined by photoperiod, and the geographic races responded to
different photoperiods [8,126].  This indicated genetic control and
genetic differences between the races.  Not all the races were able to
acclimate in time to avoid winter cold injury in Minnesota, but once
cold acclimated, all the races were able to withstand -130 degrees F
(-90 degrees C) without injury.  Another study [8], however, indicates
that clones from Montana, Oregon, and Idaho have different hardiness
levels than clones from North Dakota and Washington.

Comparisons of the timing of fall events between different climatic
races of red-osier dogwood growing at the same location in Minnesota are
as follows (Onset of rest is the point in the growth cycle beyond which
plants or cuttings moved into a favorable environment will not grow)
[127]:

                   Onset of Rest   Red bark Color   50% leaf Abscission
Seattle, Wash.       Oct. 15           Nov. 2              Nov. 6
Cadillac, Mich.      Aug. 18           Oct. 10             Oct. 31
Moscow, Idaho        Aug. 31           Oct. 10             Oct. 31
Wayland, Mass.       Sept. 17          Oct. 4              Oct. 31
Excelsior, Minn.     Aug. 30           Oct. 10             Oct. 27
Ottawa, Ontario      Aug. 18           Sept. 20            Oct. 27
Madison, Wisc.       Sept. 2           Oct. 3              Oct. 27
Dickinson, ND        Aug. 10           Sept. 20            Oct. 21
College, Alaska      Aug. 10           Aug. 10             Oct. 17
Dropmore, Manitoba   Aug. 10           Sept. 19            Oct. 14

Flowering times for red-osier dogwood in some western states are as
follows [28]:

                 Utah    Colorado    Wyoming    Montana   North Dakota
Begining of
  Anthesis:      May       May        June        May          May
Anthesis:        June      June       July        July         June
End of 
  Anthesis       July      July       August      July         July

Comparisons of spring phenology in different parts of the country
include [9,47,99,131]:

                   Leafing Out       Blooming        Fruit ripe
Massachusetts                          May             mid-July
n Minnesota                          June-August       
n Idaho           late April-May      May-June      late July-August
Great Plains                           June         August-September

Related categories for Species: Cornus sericea | Red-Osier Dogwood