Plant Guide
REDTOP
Agrostis gigantea Roth
Plant Symbol = AGGI2
Contributed by: USDA NRCS Idaho Plant Materials
Program
Figure 1. Redtop (Agrostis gigantea). Photo by Robert Soreng @
USDA-NRCS PLANTS database.
Alternate Names
Agrostis alba auct. Non. L.
Agrostis depressa Vassey
Agrostis palustris Huds.
Agrostis stolonifera L. var. major (Gaudin) Farw.
Black bent
Carpet bentgrass
Redtop bent
Redtop bentgrass
Redtop has undergone numerous name changes over time,
and the actual placement of the multiple species and
varieties remains confused due to hybridization.
Linnaeus apparently based the original description of
Agrostis alba on a specimen of Poa nemoralis
(Hitchcock, 1971). Historically, several varieties have
been described, yet other authors have combined A.
gigantea under a broader A. stolonifera (creeping
bentgrass) (Cronquist et al., 1977). Currently the
PLANTS database recognizes A. gigantea as a separate
species from A. stolonifera with A. gigantea being
primarily rhizomatous while A. stolonifera typically
produces stolons. This plant guide addresses A. gigantea
in the broad sense which includes earlier treatments of A.
stolonifera var. major.
Uses
Livestock:
Cattle prefer nearly all other cultivated grasses to redtop.
It remains green summer long and is useful in western
states in pasture plantings in mountain meadows. It is
considered preferred feed for cattle and horses in spring
and summer and a desirable feed in fall and winter. It is
considered a preferred feed for sheep in spring and a
desirable feed in summer (Ogle and Brazee, 2009).
Hay: One of the primary uses of redtop is for grass hay.
Turf:
Though creeping bentgrass (A. stolonifera) is much more
prevalent in the turf industry than redtop, this species is
used throughout North America and Europe in lawns and
golf courses. It is also used for overseeding as a winter
lawn grass in the South East.
Erosion control:
Redtop is commonly used for erosion control in plantings
along riparian zones and wetlands. It germinates very
rapidly and performs well on acidic low fertility soils. Its
root system is well suited for holding soils on wetlands,
waterways, ditchbanks and burned or cutover-timberland
(Wasser, 1982).
Revegetation:
This species has been used to recapture sites which are
very acid to land affected with heavy metals and poor soil
quality such as mine spoils. It has been shown to have a
higher tolerance of acidic soils than Kentucky bluegrass
(Balasko et al., 1995).
Wildlife:
Redtop is a preferred feed for elk in spring, but is used
sparingly by deer (Ogle and Brazee, 2009). It is
commonly used as cover by numerous species of birds
and small mammals. Ducks and geese use redtop for
nesting cover, and it is grazed by geese.
Status
Consult the PLANTS Web site and your State Department
of Natural Resources for this plant’s current status (e.g.,
threatened or endangered species, state noxious status,
and wetland indicator values).
Weediness
Redtop has been described as weedy or invasive in some
states and European countries. It may become weedy or
invasive in some regions or habitats and may displace
desirable vegetation if not properly managed. Consult
your local NRCS Field Office, Cooperative Extension
Service office, state natural resource, or state agriculture
department regarding its status and use. Weed
information is available from the PLANTS Web site at
plants.usda.gov
Description
. Consult related web sites on the Plant
Profile for this species for additional information.
Figure 2. Line drawing of redtop. Hitchcock, A.S. (rev. A. Chase). 1950.
Manual of the grasses of the United States. USDA Miscellaneous
Publication No. 200. Washington, DC
General:
Grass family (Poaceae). Redtop is a cool season (C-3),
sod-forming, perennial grass native to Europe (Wasser,
1982). The plant produces culms up to 4 feet in height
which can be erect, decumbent or semi-prostrate in form.
The leaf blades are flat, folded or curled, approximately
1/8 to 3/8 inches wide with a prominent ligule at the
junction of the leaf blade and sheath. The inflorescence is
an open panicle with ascending branches. The spikelets
are small with the lemma reaching 0.08 inches long
(Cronquist et al., 1977). The name redtop is derived from
the reddish coloring of the panicle. The scaly, creeping
rhizomes make a coarse, but fairly dense turf. The roots of
redtop can reach 4 ft deep under favorable conditions
(Troughton, 1957). There are approximately 4.85 million
seeds/lb (USDA NRCS, 2010).
Distribution:
Redtop is native to Eurasia and North Africa and was
introduced to North America in the 18th century as a lawn,
meadow and pasture grass (Monsen et al., 2004). It has
since become naturalized and widely distributed
throughout the U.S. and Canada. It grows better in the
moist mountain areas of the West and humid areas of the
Northeast than in the warmer climates of the southern
states. For current distribution, consult the Plant Profile
page for this species on the PLANTS Web site.
Habitat:
Redtop has been cultivated and planted extensively
throughout North America and has been widely
naturalized in numerous habitats. It occurs in areas with
shallow water, wet meadows and stream banks from sea
level to 8,000 ft (Monsen et al., 2004). Redtop can be
found growing in pure stands or with other wetland/wet
meadow species such as sedges, rushes, and other grasses.
It is also common in riparian areas growing in association
with cottonwood, alder and willow species.
Adaptation
This species is broadly adapted to a wide range of soil and
weather conditions. It thrives in cool moist habitats and is
best adapted to the northern states but has been
successfully established throughout North America,
especially with management and irrigation.
Redtop is best adapted to mesic to semi-hydric soils, and
is well suited to areas receiving 18 to 40+ inches mean
annual precipitation. The plants are tolerant of poorly
drained and sub irrigated sites and sites that are frequently
flooded.
This species performs best on clay loam to loamy soils,
but under irrigation will perform on nearly any soil type
with the exception of limestone based soils. Redtop is
adapted to soils with a pH of 4.5 to 8.0. It has a low
tolerance to salinity.
Redtop displays good grazing resistance due to its
rhizomes, its low palatability and semi-prostrate growth
form. Stands of redtop often increases in pasture mixes
and will decrease under light to non-grazed situations.
Establishment
Redtop can be established by seed, sprigs, or sod. For
seeding, plant at a depth of 0-1/4 inch into a smooth, firm,
well-drained, weed free seed bed. For turf plantings, seed
at a rate of approximately 1 lb/1000 ft². For pasture and
range plantings a rate of 0.5 lbs/ac is recommended (Ogle
et al., 2009). Broadcast and lightly harrow to cover seed.
Compaction of soil over seed may cause crusting which is
impenetrable by seedlings. Use of an inert carrier or
dilutent when drill seeding can improve seed flow and
metering small seed such as redtop.
The soil surface should be kept moist during
establishment. Early fall seeding is recommended which
allows a minimum of 45 growing days prior to frost for
good establishment if irrigation is available. If irrigation
is not available, an early spring seeding is recommended.
Do not apply nitrogen until the second growing season.
Seedlings have low vigor and seeding often results in
poor stands; however, once established, stands of redtop
will readily spread and persist for many years (Monsen et
al., 2004).
Redtop is seldom seeded alone. Better forage and high
quality hay is produced if redtop is mixed with species
such as timothy, creeping foxtail and/or clover species.
Redtop grows rapidly after seeding and excessive seeding
rates are not recommended, particularly in mixtures.
Management
Stands of redtop should not be grazed until the plants are
at least 8 inches tall. Pasture mixes will need to be grazed
closely in a rotation to keep plants producing palatable
regrowth on wet and sub-irrigated sites. Redtop should
not be grazed closer than three inches (USDA NRCS,
1995).
Cut hay in early flowering stage for best quality. Forage
contains 8 to 9 percent protein when cut at full bloom and
12 to 14 percent when cut before bloom. (USDA-NRCS,
1995).
Stands respond well to applications of fertilizer and lime.
Low fertility critical areas should be fertilized prior to
seeding.
Pests and Potential Problems
Redtop is known to develop ergot which can lead to
livestock poisoning (Ontario, 2010). This species can also
develop leaf rusts, spotting and snow mold, but these have
generally not been a problem (Wasser, 1982).
Environmental Concerns
Redtop is an introduced species which can displace native
vegetation under ideal conditions. It should not be planted
in sites where revegetation of native species is desired. It
hybridizes with other Agrostis species, so numerous non-
typical plants can be found in most populations.
Seeds and Plant Production
Seed production fields should be soil tested before
planting to determine soil nutrient levels and fertilizer
needs.
Stands should be combined or swathed when plants are in
the hard dough stage. Seed shatters readily, so delaying
harvest can significantly reduce yields. Seed should be
cleaned with air screens or clippers with a 28x28 upper
screen and 50x50 lower screen (Wasser, 1982).
Seed production fields yield approximately 75 lbs/ac with
90 percent purity and 90 percent germination (Monsen et
al., 2004).
There are approximately 4,850,000 seeds per pound.
Cultivars, Improved, and Selected Materials (and area
of origin)
There are several released materials of the stoloniferous
creeping bentgrass, which are used readily as lawn and
golf course varieties. There is currently only one known
released variety of redtop.
‘Streaker’ redtop was released in 1982 by Jacklin Seed
Company and Lofts Seed. It was chosen from among 21
lots of seed which were evaluated for uniformity, vigor,
seed yield and mechanical purity and cleanliness. It’s
intended use is for overseeding of dormant warm season
grasses; low maintenance turf, reclamation and pasture
(Alderson and Sharp, 1994).
References
Alderson, J. and W. C. Sharp 1994. Grass varieties in the
United States. Agriculture Handbook No. 170. USDA,
SCS, Washington, DC.
Balasko, J.A., G.W. Evers, and R.W. Duell. 1995.
Bluegrasses, ryegrasses, and bentgrasses. In: Barnes,
R.F., Miller, D.A. and C.J. Nelson. Forages. 5th ed.
Iowa State University Press. Ames, IA.
Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L.
Reveal, and P.K. Holmgren. 1977. Intermountain
Flora. Vol. 6. The monocotyledons. Columbia Univ.
Press, NY.
Hitchcock, A.S. 1971. Manual of the grasses of the
United States, 2nd edition. Dover Publications, Inc.
New York, NY.
Monsen, S.B., Stevens, R. and N. Shaw. 2004. Grasses.
In: S.B. Monsen, R. Stevens, and N.L. Shaw
[compilers]. Restoring western ranges and wildlands.
Fort Collins, CO: USDA_FS-RMRS. General
Technical Report RMRS-GTR-136-vol-2. p. 295-424.
Ogle, D., and B. Brazee. 2009. Estimating initial stocking
rates. USDA-NRCS, ID-TN 3. Boise, ID.
Ogle, D., L. St. John, M. Stannard, and L. Holzworth.
2009. Grass, grass-like, forb, legume, and woody
species for the Intermountain West. USDA-NRCS,
ID-TN 24. Boise ID.
Ontario. 2010. Poisoning of livestock by Plants-Fact
Sheet. Ontario Ministry of Agriculture, Food and
Rural Affairs. Ontario, Canada.
Troughton, A. 1957. The Underground Organs of
Herbage Grasses. Commonwealth Agricultural
Bureaux. Farnham Royal, Bucks, England.
USDA Forest Service. 1937. Range Plant Handbook.
Washington, D.C.
USDA NRCS. 1995. Hay and pasture management of
redtop. USDA-NRCS. Columbia, MO.
USDA NRCS. 2010. The PLANTS Database [Online].
Available at http://plants.usda.gov (accessed 19
January 2010). USDA-NPDC, Baton Rouge, LA.
Wasser, C.H. 1982. Ecology and culture of selected
species useful in revegetating disturbed lands in the
west. USDI-FWS. Biological Services Program.
FWS>OBS-82/56.
Prepared By
Derek Tilley; Range Scientist, USDA NRCS Plant
Materials Center, Aberdeen, Idaho.
Dan Ogle; Plant Materials Specialist, USDA NRCS,
Boise, Idaho.
Loren St. John; Team Leader, USDA NRCS Plant
Materials Center, Aberdeen, Idaho.
Citation
Tilley, D., D. Ogle, and L. St. John. 2010. Plant guide for
redtop (Agrostis gigantea). USDA-Natural Resources
Conservation Service, Idaho Plant Materials Center.
Aberdeen, ID. 83210.
Published July, 2010
Edited: 07Apr2010 djt; 07Apr10 dgo; 20Jan2010 lsj
For more information about this and other plants, please
contact your local NRCS field office or Conservation
District at http://www.nrcs.usda.gov/ and visit the
PLANTS Web site at http://plants.usda.gov/ or the Plant
Materials Program Web site http://plant-
materials.nrcs.usda.gov.
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