BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Agave lechuguilla | Lechuguilla 



GENERAL BOTANICAL CHARACTERISTICS : 
Lechuguilla is a perennial, evergreen leaf succulent.  Up to 50 thick
and rigid, ascending to erect, sharply pointed, linear-lanceolate, light
green to yellow green, 10- to 20-inch-tall (25-50 cm) leaves form a
basal rosette [15].  Lechuguilla often occurs in extensive colonies with
several thousand rosettes per acre because clones or offsets are
produced on rhizomes [15,23].  Rhizomes are fleshy and thick, and the
roots are fibrous and shallow, seldom extending more than 4 or 5 inches
(10-12 cm) below the soil surface [23,24].  Individual rosettes flower
once and then die.  When they flower, the central bud of the rosette
grows into a 8- to 11.5-foot-tall (2.5-3.5 m) stalk, with purplish or
yellow flowers occurring in clusters in a spikelike panicle at the apex
[15,35].  The fruit is a brown to black, oblong nearly cylindrical
capsule, about 0.6 to 1.0 inch (1.5-2.5 cm) long [35].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte
   Geophyte


REGENERATION PROCESSES : 
Reproductive Strategy:  Because lechuguilla occurs in an environment
where seedling survival is rare, it reproduces almost entirely by
rhizomes, with populations composed primarily of a series of clones
[10,12].  Nevertheless, lechuguilla produces large numbers of seeds, and
sexual reproduction may occasionally occur when conditions for
germination and seedling establishment are optimal.

Vegetative reproduction:  Young offset clones are produced by rhizomes
of the parent plant [23].

Flower and fruit production:  Individuals are monocarpic, flowering only
once at the end of the plant's life cycle, which may be between the age
of 3 and 20 years [11,31,35].  In general, populations flower
extensively each year [11].  Flowers are pollinated by numerous insects
and animals which feed on the sweet nectar.  Pollinators include moths,
bees, wasps, beetles, bats, and hummingbirds [11,23].  Many capsules are
produced along a spikelike panicle, each producing up to several hundred
seeds [10].

Seed dispersal: The erect capsules are longitudinally dehiscent.  The
seeds are gradually shaken out of the cracks by animals and wind [15].
Most seeds fall near the parent plant, but strong winds may blow some
seeds several hundred feet [15].  

Germination and establishment:  Lechuguilla seeds are not dormant and
may germinate as soon as they fall to the soil surface if moisture is
sufficient [10].  Light is not required for germination.  In laboratory
experiments, seeds germinated well whether placed on the soil surface or
buried beneath soil [10].  Optimal germination temperatures are between
77 and 86 degrees F (25-30 C), although seeds will germinate over a
broad range of temperatures (59 to 104 degrees F [15-40 C]) [10].  Only
about 50 percent as many seeds germinate if temperatures are 21.6
degrees F (12 C) below optimum or 14.4 degrees F (8 C) above optimum
[23].  Germination is suppressed by alternating temperatures which
include exposure to 104 degrees F (40 C) for only 4 hours each day [11].
Under natural conditions, germination appears to occur primarily in
protected microhabitats toward the end of the summer rainy period when
soil temperatures are close to those optimal for germination [23].


SITE CHARACTERISTICS : 
Lechuguilla is restricted to the Chihuahuan Desert.  It is most commonly
found above the shrubby plains, on rocky, limestone derived soils of
mountain slopes, foothills, bajadas, and mesas [4,11,15].  These
habitats are often dominated by leaf (Agave spp., Hechtia spp.) and stem
(Yucca spp., Dasylirion spp.) succulents [4].  Lechuguilla may be the
primary plant, with dense stands averaging up to 12,145 rosettes per
acre (30,000/ha) [15] or it may codominate with other shrubs, such as
smooth sotol (Dasylirion leiophyllum), creosotebush (Larrea tridentata),
skeleton goldeneye (Viguiera stenoloba), oneseed juniper (Juniperus
monosperma) and ocotillo (Fouquieria splendens) [7,8,14,29,36].  Other
common associates include grama grasses (Bouteloua spp.), threeawns
(Aristida spp.), cacti (Opuntia spp.), mariola (Parthenium incanum),
rocktrumpet (Macrosiphonia spp.), and smallseed sacahuiste (Nolina
microcarpa) [7,8,14,29].

Soils:  Lechuguilla is primarily restricted to light-colored and highly
calcareous, limestone-derived soils [10].  It occasionally occurs on
igneous and sandy substrates, but on these soils, populations are much
less dense [11].  Limestone soils may be derived from either primary
sedimentaries or caliche [15].  Lechuguilla is usually absent from
volcanic areas [15].  In Big Bend National Park, smooth
sotol-lechuguilla-dominated communities occur on both limestone and
igneous rock, with soil textures of fine sands, silts, and silt-clay
loams [7].  The pH of igneous and limestone soils in Big Bend National
Park is similar, ranging from 8.0 to 8.9 [7].

Elevation:  Lechuguilla occurs from about 972 to 5,906 feet (300-1,800
m) in elevation [12] but is most common below 4,922 feet (1,500 m) [11].
Along the Guadalupe Escarpment in New Mexico and Texas, lechuguilla is
usually the dominant shrub between 3,800 and 4,600 feet (1,158 and 1,402
m) [14].  At elevations above 4,000 feet (1,219 m), lechuguilla often
occurs in the understory of oak chaparral (Quercus grisea, Q. gravesii)
and woodlands which may be dominated by Mexican pinyon (Pinus
cembroides), ponderosa pine (P. ponderosa), alligator juniper (Juniperus
deppeana), oneseed juniper, Texas madrone (Arbutus texana), and bigtooth
maple (Acer grandidentatum) [7,36].


SUCCESSIONAL STATUS : 
Obligate Climax Species

Lechuguilla is characteristic of climax Chihuahuan Desert shrub
communities. 


SEASONAL DEVELOPMENT : 
New lechuguilla leaves unfold from the central spike during the
relatively wet summer and early fall.  About one new leaf unfolds per
month during this time of the year, for a total of about six or seven
new leaves per plant over the entire year [24,27].

During most years flowering occurs during May and June; however,
flowering may be infrequent or extend as late as October if the
preceeding rainy season or winter was particularly dry [11].  Near El
Paso, Texas, flower shaft growth was found to be rapid, peaking at 7.8
inches (20 cm) per day and reaching an average shaft length of 8.5 feet
(2.6 m) in 3 to 4 weeks [11].  Resources for flower stalk growth are
drawn mainly from the leaves.

Related categories for Species: Agave lechuguilla | Lechuguilla