BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Scirpus americanus | Olney Threesquare 



GENERAL BOTANICAL CHARACTERISTICS : 
Olney threesquare is a coarse, rhizomatous, perennial sedge.  It has
erect, sharply triangular and deeply concave-sided culms growing up to 5
feet in height (1.5 m) [10,21].  It generally bears only a few short
leaves up to about 4 inches long (10 cm) which arise from the lower part
of the culm.  The inflorescence consists of a cluster of 5 to 12
sessile, crowded spikelets [28].  Rhizomes are located within 6 inches
(15 cm) of the soil surface [28].


RAUNKIAER LIFE FORM : 
   Geophyte
   Helophyte


REGENERATION PROCESSES : 
Sexual reproduction:  Olney threesquare seed production has been
variously reported as very poor to heavy, with seed yields ranging from
0 to 24 pounds per acre (0-27 kg/ha) [28].  The seeds undergo a long
period of afterripening, often requiring 18 months or more before
germination can occur.  The seeds remain dormant as long as they are
submerged in water and thus become a component of the marsh seed bank.
Germination and seedling establishment potentially occur on exposed
mudflats following marsh drawdown, yet seedling establishment under
these natural conditions appears to be rare [19].  Under laboratory
conditions, maximum germination of only 25 percent was achieved in
distilled water under fluctuating temperatures between 68 and 95 degrees
Fahrenheit (20-35 deg C) [20].  Germination decreased with increasing
salinity with a 50 percent reduction at 4 parts per thousand (ppt) and
no germination at above 13 ppt [20].

Vegetative regeneration:  Olney threesquare perennates and spreads by
rhizomes, which is primarily responsible for the maintenance and
expansion of stands.


SITE CHARACTERISTICS : 
In coastal regions, Olney threesquare grows primarily on peat in
brackish tidal marshes, where soil salinities range from 2 to 17 ppt,
and water levels range from -2 to +4 inches (-5 to +10 cm) [11,18].
Inland, it primarily grows in marshes, wet meadows, and playas that are
somewhat alkaline, but also grows in fresh water [6].  In an alkali
meadow in Utah, Olney threesquare dominated the area surrounding the
water source (a spring), but became rarer farther away from the spring,
and was replaced by inland saltgrass and creeping spikerush as water
depth decreased and salinity increased [26].  At this Utah meadow, soils
under Olney threesquare stands had higher levels of organic matter and
phosphorus than other marsh plant communities.


SUCCESSIONAL STATUS : 
Obligate Initial Community Species (Gulf Coast)
Obligate Climax Species (Atlantic Coast and western U.S.)

The successional status of Olney threesquare varies regionally.  Along
the Gulf coast, it is a seral species, and gives way to seashore
saltgrass and marshhay cordgrass in the absence of periodic (every few
years) burning or other disturbance.

In Utah, Olney threesquare is considered climax.  Referring to Olney
threesquare stands at Fish Springs, Utah, Bolen [2] stated "Scirpus
olneyi stands contain no other marsh species of comparable status and
are considered to represent closed stands of vegetation.  It is
completely successful in its niche and competition from other
communities and/or species was not observed."  

Along the East Coast, Olney threesquare forms climax stands that are
apparently maintained more by the slowly rising sea level than by fire
[28].


SEASONAL DEVELOPMENT : 
In Louisiana, Olney threesquare begins spring growth in March when soil
temperatures 4 inches (10 cm) below the soil surface reach 60 degrees
Fahrenheit (16 deg C) [11,19].  Culms grow at a uniform rate until
August, but by October, nearly all the culms are dead.  A small
percentage of the culms remain green throughout the winter [19].

In Utah, spring growth began on March 27 in marshes near warm springs,
and on April 14 in marshes far-removed from warm water [2].

Flowering and fruit production dates are as follows:

Delaware - flowers from early June to September [28]
New England - flowers from July 20 to August 8 [25]
Louisiana - flowering begins in late March and is finished by late May.
            Seeds are ripe by the end of June.  Seedfall begins in
            mid-July [19].
North and South Carolina - flowers from June to September [21]
Utah - flowers in early May [2]

Related categories for Species: Scirpus americanus | Olney Threesquare