keys to the vascular plants of east texas - Botanical Research ...

1034 POACEAE/PIPTOCHAETIUM
sometimes weedy colonies covering large areas (often excluding other vegetation); nearly
throughout East TX w to Cross Timbers and Prairies (Borowski et al. 1996); se U.S. from MD s to
FL w to AR and TX, also OR. We have seen only one flowering collection from East TX. Native
of China. [Bambusa aurea Hort] Like many bamboos, Phyllostachys species generally flower
synchronously only after intervals of many years. In some species, these flowering cycles are up
to 120 years in length, apparently based on an internal physiological calendar (Janzen 1976;
Judd et al. 1999). Janzen (1976) reported the intermast period (= time period between successive
fruit/seed production events) in P. aurea to be “28–29 (2� 14–15)” years, based on specimens cultivated
in Europe. However, he also indicated that cultivation and other factors can affect the
flowering interval. Texas plants may thus have lost synchrony and not display such a flowering
pattern. It has been hypothesized that such long intervals between flowering evolved as a
mechanism to escape seed predation (Janzen 1976). Large amounts of seed produced at intervals
would hinder the buildup of populations of seed predators and lead to satiation of any
seed predators present—only so much can be eaten at one time and thus many seeds would escape
predation. This species was introduced to the U.S. prior to 1870 (Rehder 1927) as an ornamental,
for barrier planting, and for erosion control and soil stabilization (Borowski et al. 1996).
The young shoots are reported to be “very palatable” (Barkworth & Clark ined.) and the mature
culms are sometimes used as fishing poles. I
A variety of other exotic bamboos, including Bambusa species (e.g., B. multiplex (Lour.) Raeusch.
ex Schult. & Schult. f., HEDGE BAMBOO) and additional species of Phyllostachys (e.g., P. nigra
(Lodd.) Munro, BLACK BAMBOO, with black culms) are cultivated in East TX. Our only native
bamboo, Arundinaria gigantea (GIANT CANE), occurs in moist woods and low areas from the
Pineywoods and n Gulf Prairies and Marshes w to at least Lamar Co. (BRIT) in the Red River
drainage.
PIPTOCHAETIUM J. Presl SPEAR GRASS
AA New World mainly temperate C3 genus of 36 species (Cialdella & Giussani 2002), ranging
from the U.S. to Argentina, with most in South America, and particularly abundant in Argentina
(Barkworth ined.). Migration between North and South America is thought to have occurred
during the late Tertiary Period, in association with the movement of herbivorous mammals
(Williams 1975; Thomasson 1980). Recent studies (Cialdella & Giussani 2002) suggest the
genus is monophyletic. Piptochaetium species have sometimes been put into Stipa (e.g., Gould
1975b) and also resemble species of Nassella. However, according to Clayton and Renvoize
(1986), while the genus can imitate Stipa and Nassella, “but is readily distinguished by its
grooved palea.” Also, Piptochaetium can be distinguished unambiguously from Nassella (with
strongly overlapping lemma margins) by its involute, non-overlapping lemma margins
(Barkworth 1990, ined.) and palea protruding from the lemma (versus not protruding in
Nassella) (Cialdella & Giussani 2002). (Greek: pipto, to fall, and chaite, long hair, mane, or
bristle, in reference to the deciduous awns of the type species) (subfamily Pooideae, tribe Stipeae)
REFERENCES: Hitchcock 1925; Parodi 1944; Thomasson 1978, 1980; Clayton 1983; Barkworth
1990, 1993, ined.; Tucker 1990; Cialdella & Arriaga 1998; Cialdella & Giussani 2002.
Piptochaetium avenaceum (L.) Parodi, (resembling Avena—OATS), BLACK-SEED SPEAR GRASS,
BLACK-SEED NEEDLE GRASS, BLACK OAT GRASS, OATS NEEDLE GRASS, EASTERN NEEDLE GRASS. Perennial,
tufted, (35–)50–80(–100) cm tall; ligule membranous, (0.4–)1.5–4.5 mm long; leaf blades ca.
0.8–1.5(–3) mm wide; panicles with few spikelets; spikelets 1-flowered, disarticulating above the
glumes; glumes acuminate, (9–)10–12(–15) mm long, � equal; lemma 8–12 mm long (including
callus), indurate, dark (brown or purplish) at maturity, the margins involute, not overlapping
(rounded portions abutting), with a very long (3.5–10 cm), geniculate, twisted awn; lemma apex
without a white neck or crown (as in some Nassella species) but with a fringe of brown hairs