BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Sambucus racemosa ssp. pubens | Red Elderberry 



GENERAL BOTANICAL CHARACTERISTICS : 
S. racemosa ssp. pubens is a deciduous shrub (occasionally var.
arborescens may be a small tree) from 20 inches to 20 feet (0.5 to 6 m)
in height [14,42,57,85].  Young twigs are soft and pithy, but the wood
is quite hard [70].  The stems may have a rank odor if bruised [49,113].
Elderberries have large, opposite, compound leaves with five to nine
leaflets [14,42].  The creamy white flowers are in pyramidal heads and
followed by round, berrylike fruits called drupes [14,33,42,49,63].  The
fruit normally contains two to four seeds [12] and is usually bright red,
although that of var. melanocarpa is black.

Information on differing morphology and growth forms of varieties is
summarized below [12,19,42,89,112,113].

    Var. melanocarpa has black or purplish black fruit.  The
    leaflets may be pubescent underneath, and it is usually 3 to 7 feet
    (1 to 2 m) tall.  It appears to have thicker foliage because it has
    shorter internodes.

    Var. arborescens may occasionally be a small tree, but it is
    normally a clumped shrub from 6 to 20 feet (2 to 6 m) tall which
    coppices freely.  It has bright red fruit with three poisonous seeds 
    or nutlets.

    Var. microbotrys has glabrous leaflets and may be from 20 inches
    to 6.5 feet (0.5 to 2 m) tall.  It is rhizomatous and forms clones
    which persist by vegetative reproduction.

    Var. leucocarpa is more or less stoloniferous, from 3 to 10 feet
    (1 to 3 m) tall, and usually has red fruit.  New stems are glaucus.
  


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual regeneration in S. racemosa ssp. pubens begins with small,
perfect flowers which are pollinated by insects [79], usually resulting
in three nutlets in a fleshy, edible drupe [19,42].  There are good seed
crops most years, and seeds are dispersed by birds and other animals
that eat the fruit [6,35,79].  Plants are able to reproduce by 3 to 5
years of age [44].  Elderberry seeds have a hard seed coat and dormant
embryos that delay germination [6,35,82], but heat treatment or sulfuric
acid scarification and stratification can hasten germination.  Several
authorities give detailed descriptions of seed gathering and germination
treatments [6,39,99,114,118].  Without treatment, germination of seedlings
may be delayed for 2 or more years after planting [39].

A Utah study of var. microbotrys found that only about 60 percent of the
seed was filled; 74 to 91 percent of that was viable; and 37 to 51
percent of the filled seed germinated following stratification in the
laboratory.  Germination of seed stratified under field conditions was 8
percent, and less than 1 percent of seed planted under aspen germinated.
None of the seedlings in the field survived, and the researchers
concluded that vegetative reproduction was more important to this
variety than sexual reproduction [12].

Viable seeds of S. racemosa ssp. pubens have been found buried in the
forest floor [1,32,48,54,55,66] at all sampled soil depths when soil was
stratified [48,54,55].  In Minnesota viability of the buried seeds was
25 percent [1].  A detailed study in Idaho found overall viability of
Sambucus seeds to be only 16 percent [54].  Theories about the origin of
seed found in seed banks include:  a) the seed has long-term viability
and remains from early seral stages; b) birds may bring in seed; and, c)
understory plants may occasionally produce some fruit [32,54,106].

S. racemosa ssp. pubens regenerates vegetatively from sprouts, rhizome
suckers, and layering [118].  A Utah study of vegetative regeneration in
var. microbotrys following clipping found new shoots arising from buds
at the base of old stems, but no new stems initiating from the rhizome.
When old growth was completely killed, however, numerous new stems
started from the rhizomes, suggesting that living stems growing from the
rhizome suppress rhizome bud growth.  Seedlings form a thickened crown
with buds which can become a rhizome by the third year [12].


SITE CHARACTERISTICS : 
S. racemosa ssp. pubens is not well adapted to warm climates and in the
southern part of its range is found in cooler uplands, swamps, and along
cool drainages [118].  Where its range overlaps with S. cerulea, it will
usually be found on higher, cooler sites, although they grow together in
the mountains [54,82,115].  Where it is found on upland sites, S.
racemosa ssp. pubens is relatively high in frequency and low in density,
so that the few plants are well scattered through the forest [15].  S.
racemosa ssp. pubens is found in riparian systems in California [87,90]
and in northern Ohio swamp forests [118].

Soils:  S. racemosa ssp. pubens prefers rich rocky soils with ample
moisture [13,33,113].  It will tolerate saturated soils (although not as
well as S. canadensis) [118].  In Utah growth on gravel and sand is fair,
growth on sandy loam, loam, and clay loam is good, growth on clay is
fair, and growth on dense clay is poor [9,20,24].  S. racemosa prefers
soils with a pH of 5.0 to 8.0 [118].  In Utah growth on acidic soils is
fair while growth on saline and sodic-saline soils is poor.  Best
development is on soils over 20 inches deep [20].  In Utah soils ranged
from loam to silt loam to sandy clay loam [12].  An Idaho study found S.
racemosa ssp. pubens on soils with high (5.6-8.0 percent) organic matter
[71].  A study of Douglas-fir plantations in British Columbia clearly
associates increasing frequency and cover of S. racemosa ssp. pubens
with moist, nutrient-rich soils along a gradient from very dry to moist
and nutrient-poor to nutrient-rich [53].

Elevation:  Elevational ranges in some western regions are as follows
[13,20,75]:

                            Minimum              Maximum
                         feet     meters      feet     meters
Utah                     7,300     2,225     11,000     3,353
Colorado                 5,400     1,646     11,300     3,459
Wyoming                  3,500     1,067     11,000     3,353
Montana                  3,800     1,158      8,300     2,530
California
(var. microbotrys)       6,000     1,829     11,000     3,353
California
(var. melanocarpa)       6,000     1,829     12,000     3,658
West-central Alberta     2,800       857      5,050     1,537


SUCCESSIONAL STATUS : 
In western coniferous forests S. racemosa ssp. pubens is primarily an
early to mid-seral species [48,71,104,113] which can persist in relatively
open conifer stands [4,8].  Thinning operations may produce an increase
in S. racemosa ssp. pubens, but it disappears again as overstory shade
redevelops [2].  In deciduous forests of aspen or red alder, S. racemosa
ssp. pubens may be a dominant part of a long-lived seral or climax
forest [4,40,72,73,74].  If conifers gain dominance, it disappears along
with other seral species [72].

Shade tolerance is important in determining a plant's role in
succession, and several authors list S. racemosa ssp. pubens as shade
tolerant or partially shade tolerant [35,89,112,118].  In forests with
dense shade S. racemosa ssp. pubens is chiefly found in openings with
higher light levels [6,15,70].  Where it grows under a canopy, it
develops poorly, is lower in height, and fruits sparingly, if at all
[32,71,116].  A Vermont study showed that S. racemosa ssp. pubens
presence went from 50 percent with light levels of 48 percent full
sunlight reaching the forest floor in deciduous forest to nothing when
light levels were 15 percent in boreal forest [97].  An Oregon study
along a gradient from red alder to conifer forest had similar findings
and attributed the difference to light levels [28].  S. racemosa ssp.
pubens would seem to be restricted to a seral role in dense, coniferous
forest but could be part of a climax deciduous forest community
[15,48,52,71,113].


SEASONAL DEVELOPMENT : 
In southern Quebec, Sambucus racemosa ssp. pubens flowers from April to
July, its fruit ripens from June to August, and its seed is dispersed
from June to November [66].  In the subalpine fir/beadlily (Abies
lasiocarpa/Clintonia uniflora) habitat type in northwestern Montana,
flowering is in early June with fruit set at the end of June to early
July.  Fruit ripens by late July to early August, and seed dispersal is
in September and October [121].  Flowering in Alaska is from May to July,
with fruit maturing in July and August [113].  In West Virginia fruit
ripens in early July and is dispersed by late August [77].  In Utah var.
microbotrys begins growth in early June, and flower buds begin to open
from mid-June to early July.  Fruits and seeds mature between late July
and mid-August [12].

Flowering times for S. racemosa ssp. pubens in some western states are
as follows [20]:

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

Blooming periods for the varieties of S. racemosa ssp. pubens in the
Pacific Northwest are as follows [42]:

    var. melanocarpa blooms from May to July
    var. arborescens blooms from March to July
    var. microbotrys blooms in June and July
    var. leucocarpa blooms in May and June

Related categories for Species: Sambucus racemosa ssp. pubens | Red Elderberry