BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Agrostis gigantea | Redtop 



GENERAL BOTANICAL CHARACTERISTICS : 
Redtop is an introduced, perennial, rhizomatous, cool-season,
sod-forming grass with erect, stout, stems growing 2 to 4 feet (0.6-1.2
m) tall.  The panicle is 4 to 8 inches (10-20 cm) long and notably
suffused with purplish-red.  Lemmas are rarely awned [22,29].  Rhizomes
are less than 10 inches (25 cm) long [28] and are generally shallow
[27].  Rhizomes have been reported to occur to a depth of 6 inches (15
cm) [18].  Redtop apparently intergrades with creeping bentgrass; redtop
has mostly erect culms and rhizomes, and creeping bentgrass has mostly
decumbent, stoloniferous culms.


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Redtop regenerates vegetatively and by seed.  Germination rates are
high, generally 85 percent or greater [20,61].  No pretreatment is
necessary but light is required for germination [20].  Redtop seeds are
long-lived and accumulate in a seedbank [6,38].  Germination was 91
percent after 6 years of storage [61] and 50 percent after 20 years of
storage in an uncontrolled environment [32].

Redtop spreads rapidly with strong rhizomes [26,57].


SITE CHARACTERISTICS : 
Redtop is a facultative wetland species [47].  It grows in mesic to
semi-hydric conditions and is tolerant of some flooding [57].  It is not
tolerant of drought [27].

Redtop grows on a wide variety of soil types and textures.  It is
tolerant of moderately acidic soils and soils low in calcium,
phosphorus, and potassium.  It is not suited for limey soils or
limestone sites [57]. 

Redtop grows from sea level to subalpine elevations.  In California it
occurs below 7,500 feet (2,300 m) elevation [42].  It grows up to
timberline in Montana [59].

Redtop has good cold tolerance [57].  It successfully overwintered at
Prudhoe Bay in Alaska, and in Yellowknife and the Mackenzie River region
in the Northwest Territories [27].


SUCCESSIONAL STATUS : 
Redtop is considered shade intolerant [20] to moderately adapted to
shade [27].  It occurs in some open forested areas.  Redtop colonizes
disturbed sites.  It was present on a mudflow 1 year after the May 1980
eruption of Mount St. Helens [24].  It is a pioneering species on
recently exposed gravel and sandbars [26,39].  On the peatlands of
Wisconsin, a Kentucky bluegrass-redtop association may succeed the
bluejoint reedgrass (Calamagrostis canadensis)-sedge association,
especially under heavy grazing [19].

Older stands of redtop may be replaced by forbs.  In southeastern
Illinois, forbs such as western yarrow (Achillea millefolium), goldenrod
(Solidago spp.), common eveningprimrose (Oenothera biennis), common
cinquefoil (Potentilla simplex), white sweetclover (Melilotus alba), and
yellow sweetclover (M. officinalis) invade 3- to 4-year-old redtop
fields [60].
  
In the Midwest, reed canarygrass (Phalaris arundinacea), which forms
dense monocultures and threatens natural wetlands, invades redtop
meadows and inhibits its growth in 3 to 5 months [2].


SEASONAL DEVELOPMENT : 
Redtop begins growth in early to mid-spring and matures by mid- to late
summer [57].  In New York redtop flowers from June to July [10].  In the
Northwest, the southern Appalachian Mountains, and California, redtop
flowers from mid-June to early September [8,42,52].  It flowers from
June to August in the Great Plains [23].  Rhizomes undergo the greatest
development in July [13].

Related categories for Species: Agrostis gigantea | Redtop