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The genus Agave can be intimidating
with over 300 species to choose from, so if you cannot keep them all
straight, you are not alone. These living sculptures provide
incredible design opportunities, but how can the average person sort
through all of the available species to find the best one for their
situation?
Take heart; help is available! Mary
and Gary Irish's great book, Agaves, Yuccas, and Related Plants, can
be ordered from Timber Press at (800) 327-5680, or go online at www.timberpress.com.
True agave lovers might also want
to invest in Dr. Howard Gentry's encyclopedia, Agaves of Continental
North America. This terrific resource was out of print for many
years, but is now available from the University of Arizona Press. To
order, call (520) 621-1441.
In the meantime, we have prepared
short descriptions of some agaves you might encounter in the trade.
First, here is some general information about this fascinating
genus.
Agaves produce leaves arranged in
rosettes on a nearly invisible stem. This handy arrangement allows
for efficient water channeling during the slightest rainfall. The
leaves are typically thick and full of juicy tissue, giving it a
succulent nature. Most people who handle agaves come to appreciate
(or despise) the rigid spines that may be produced on the tip and/or
the margins of the leaves. The spine arrangement, length and shape
help to differentiate between species. To the layman, it is the
arrangement of the spine imprint upon the bottom of the leaf that
provokes lust and admiration for these plants. Many species bear
this imprint for life.
Nearly all of the agaves bloom only
once, at the end of their life cycle. Maturation time varies with
species and cultural practices, but generally ranges from 8 to 25
years. You really can kill these plants with kindness; ample
fertilization and irrigation can cause plants to mature more
rapidly.
The impressive flower spikes of
larger species can reach a height of 30 feet, and grow up to 3
inches a day. Most experts group agaves by the form of the
inflorescence, i.e., whether the inflorescence (essentially the
flower stalk) is an unbranched spike form (spicate) or a branched
form (paniculate).
Some species produce little plant
off-sets from underground stems known as rhizomes (these little
plants are known as pups in the trade) to keep the population going,
while others grow only as solitary plants. Some plants produce
bulbils (which are small clones of the mother plant) on the flower
stalk or inflorescence. Other species only reproduce from
seed.
Agaves prefer full sun to filtered
shade, deep and infrequent irrigation, and require well-drained
soil. They are ideal choices for containers or shallow planters with
limited soil volume. Agaves are relatively problem-free, except for
the aggravating agave snout weevil (sometimes referred to as sisal
weevil). This destructive and voracious insect seems to prefer the
larger, broad-leafed species. Infested plants will show leaf wilt,
followed by total collapse of the plant. If this occurs, promptly
remove and destroy the infected plant, as well as any weevils and
grubs you can find. Drenching the soil with a systemic insecticide
can help control problems as well. Be sure to check with your county
extension agent for appropriate control measures.
Agave
americana
(Century Plant) This giant has probably scared off more people
from planting agaves than any other species. It is relatively fast
growing, to about 6 feet tall by 8-10 feet wide. The wide, grey
leaves have stiff terminal spines and recurved teeth along the
margins. It is hardy to about 15° F. Unfortunately, it is the most
popular menu item for the agave snout weevil. As with most
agaves, the tall stalk of spectacular golden flowers signals the end
of the mother plant's life cycle, but this species pups freely.
Agave americana var.
marginata
This has creamy yellow stripes along the leaf margins. This
plant is fairly common in the trade.
Agave
americana var. mediopicta
This plant has been around for a long
time, but it hasn't been widely available. In fact, quantities are
still somewhat limited, so be sure to check availability if you plan
to use large numbers. This selection of Agave americana has a wide
cream-colored stripe down the center of the blue-green leaves. The
leaves have a wonderful arching form, similar to that of Octopus
agave (Agave vilmoriniana). The leaves are armed with a stout
terminal spine, and have teeth along the margins. This selection
seems to be smaller in stature than the regular Agave americana, to
about 4 feet tall and wide. It prefers full sun and well-drained
soil, and performs well in containers. It is hardy to at least 15°
F. As with nearly all agaves, blooming signals the end of the
plant's life cycle. However, this variety produces pups (offsets) to
keep the population going.
Agave angustifolia var. marginata
Native
to tropical Costa Rica and Mexico, this light green and cream
variegated agave is cold-hardy to about 25° F. The stiff leaves are
about 1 ˝ inches wide, with creamy yellow stripes along the
margins. This species forms clumps to 3 feet tall and wide. It
tolerates full sun, reflected heat, and part shade exposures.
However, the plant looks best when grown in filtered shade. It
can also handle more water than most agave species.
Agave
bovicornuta
Cow's horn agave is one of the most
ornamental agave species in cultivation. This fast-growing plant has
broad dark green leaves that are edged with decorative brown teeth.
This solitary agave reaches a mature size of 3-4 feet tall and wide.
Since full sun or reflected heat exposures can result in some
sunburn on the leaves, a filtered shade exposure is ideal. It makes
a stunning container plant! Agave bovicorunta is
cold-hardy to 20°F. After flowering, it will need to be
replaced.
 Agave
bracteosa
This is a relatively small growing species of agave
that rarely exceeds 12 inches in height. New plants are
produced from rhizomes or from the leaf axils often producing a
large mound on older plants. The virtually spineless pale
green leaves resemble a melted broadsword gracefully arching from
the rosette. Native to the Mexican states of Coahuila and
Nuevo Leon, this plant is not frequently in cultivation. It is
one of the few that does not die after blooming.
Agave colorata
This medium-sized agave
forms low clumps, to 3 feet tall by 4 feet across. Its striking
blue-grey leaves are short and broad, with intricate markings. They
are edged with large, dark brown teeth. Native to Sonora, Mexico,
this plant is reliably cold-hardy to 15° F. It has a slow to
moderate growth rate, and thrives in full sun and reflected heat
exposures. It also works in coastal areas, provided that
drainage is excellent.
Agave desmettiana
Often confused with Octopus agave, this
fast-growing plant is smaller in stature, to about 3 feet tall and
wide. Its soft, fleshy leaves are light green in color, and have no
teeth along the margins. However, the leaves do have a stout
terminal spine. Although it can tolerate full sun and reflected
heat, it looks more attractive in filtered shade. In coastal
regions, it handles full sun easily. Agave desmettiana
needs well-drained soil, and can be planted in the ground or in
containers. Like most agaves, it blooms only once, and then
dies. However, blooming doesn't occur for about 10 years, and
the plant produces an abundance of small "pups", to keep
the population going. This species is cold hardy to 25°F..
Agave desmettiana 'Variegata'
A newer selection, has a narrow band of yellow along the leaf margins.
Both selections sucker prolifically.
Agave
geminiflora
Winner of the popularity contest, this
versatile agave tolerates a wide range of exposures, from full sun
to full shade. Twin-flowered agave is a solitary plant, rapidly
forming a 3-4 foot symmetrical rosette of narrow, dark green leaves.
The smooth leaves have a terminal spine, and the margins are often
edged with fine white fibers. When grown in some shade the leaves
are arching and flexible, so the terminal spines are not a big
safety concern.
Twin-flowered agave has amazing
versatility, tolerating exposures ranging form full sun and
reflected heat to full shade. This accent plant forms a dense
symmetrical rosette of narrow, dark green leaves, to about 3 feet
tall and wide. In full sun, the leaves are stiff and straight,
and the terminal spines can be a hazard. In shady exposures,
the leaves reflex to form a softer silhouette. As with most
agaves, this plant blooms once, and then dies. At the end of
its life cycle, which averages about 10 years in cultivation, this
plant will send up a spectacular 15-18 foot tall flower spike.
Twin-flowered agave should be planted in well-drained soil, and
receive minimal irrigation. Although it suffers frost damage
at 20° F, gardeners in colder climates can plant Agave
geminiflora in portable containers and move them indoors when
temperatures plummet.
Agave havardiana
This agave is native to rocky grasslands in west Texas and northern
Mexico, at elevations of 4000 to 6000 feet. The stout grey leaves
are armed with marginal teeth and a sharp terminal spine. Single
plants can reach a size of 2 ˝ feet tall by 4 feet wide, and
occasionally produce offsets. It is quite cold-hardy, to at least
10° F, and prefers full sun exposures. In the low deserts,
some light shade is beneficial.
 Agave murpheyi
Those of you
in cold climates will appreciate Agave murpheyi's ability to
tolerate temperatures down to at least 10° F. This Arizona native
has narrow grey-green leaves, reaches a medium size of 3 feet tall
and wide, and produces offsets. Plant Agave murpheyi in full sun for
best growth and form.
Agave ocahui
This cold-hardy native of Sonora,
Mexico, handles temperatures to at least 15° F. Symmetrical and
compact, this attractive agave forms a tight rosette to 2 feet tall
and 3 feet across. To ensure a tight, compact form, plant it in full sun or
reflected heat exposures and water sparingly. Its stiff, dark green
leaves are about 1 inch wide, with smooth margins and a sharp
terminal spine. Agave ocahui does not produce offsets.
 Agave palmeri
(Palmer agave)
This high-elevation agave tolerates temperatures as
low as 10° F, and probably lower. It forms compact rosettes to 3
feet tall by 4 feet wide. The blue-green lance-shaped leaves are 2
feet long by 4 inches wide, with reddish teeth along the margins.
This plant is solitary is the wild, but sometimes produces offsets
under cultivation. At the end of its life cycle Agave palmeri will
send up a spectacular branched flower stalk to 10 to 18 feet tall.
Plant Agave palmeri in full sun and well-drained soil, and away from
high traffic areas, as its terminal spines are wicked. Like other
agaves and yuccas, this species is susceptible to the agave snout
weevil
Agave parrasana
This cold-hardy little agave is native to
Coahuila, Mexico, at elevations from 4500 to 8000 feet. It is very
similar in appearance and growth habit to the more common Agave
parryi. This solitary plant forms a tight rosette 2 feet tall and
wide. The stout grey leaves are edged with small teeth, and end in a
sharp spine. It is cold hardy to at least 15° F, and tolerates full
sun to part shade exposures.
Agave parryi var. truncata
(Artichoke agave) Many
people have fallen head over heels for this plant after seeing it
growing at the Huntington Botanical Garden. The dense symmetrical
form and wide blue-grey leaves make this one of the most ornamental
agaves available. Found only along the Durango-Zacatecas border in
Mexico, this agave grows in grasslands at 7500 feet in elevation,
and is hardy to about 10° F. Although this agave forms large
colonies, individual plants will grow to about 3 feet tall and wide.
Plant in full sun or light shade.
Agave scabra
(Rough leafed agave)
Agave scabra has thick, wide, gray-green leaves that are rough on
the back. The leaves are edged with recurved teeth and end in a
stout terminal spine. Although there is great variation in the wild,
the selection we are growing forms a rosette to 3-4 feet tall and
wide, and suckers freely. It is a smaller alternative to Agave
americana. Agave scabra is abundant in the Chihuahuan Desert region
of northeastern Mexico, from elevations of 3600 to 5700 feet. Plants
will thrive in full sun and reflected heat. Agave scabra is hardy to
at least 15° F.
Agave schidigera Durango Delight™
Symmetrical and compact,
this selection of Agave schidigera is sure to become a
favorite for tight planting spaces, and as a container plant. This single agave forms a dense rosette of bright green,
swordlike leaves to 2 feet tall by 3 feet wide. The smooth-edged
leaves are decorated with white markings and marginal fibers, and
end in a sharp spine. It thrives in full sun exposures, but can also
tolerate light shade. It is hardy to at least 15° F.
Agave sisalana
(Hemp plant) Sisal, or hemp, is one of the most widely-produced
natural fibers in the world. This agave is a major crop in Chiapas,
Mexico, where it is believed to have originated. It is also a
striking ornamental plant, producing bold rosettes of wide green
leaves. Be sure to allow this agave plenty of room to develop. It
grows quickly to at least 6 feet tall and wide. The leaves have no
teeth, but do have a sharp spine at the tip. Agave sisalana is only
hardy to about 25° F.
 Agave victoria-reginae
(Queen Victoria agave)
This petite agave is one of the best choices for containers or small
planting areas. Its short, stout leaves are deep green with white
markings, and form a tight rosette to 18 inches across. Queen
Victoria agave is very slow-growing and long-lived, taking many
years to reach flowering size. Plant it in full sun and water
sparingly to maintain the tightest form. Hardy to at least 10° F,
this species is native to the Chihuahuan Desert, at elevations from
4000 to 5000 feet.
Agave vilmoriniana
(Octopus agave) The most
user-friendly agave, this fast-growing species is completely unarmed
and can be used in pedestrian areas such as entries, patios, and the
perimeters of swimming pools. Its unusual light green, arching
leaves have made it a favorite of landscape designers. Octopus
agave forms a loose, open single rosette to 6 feet tall and
wide. It handles full sun in coastal regions, and looks best
if it receives some shade in low deserts. At the end of its
life cycle, it sends up a spectacular spike of golden flowers.
It is cold hardy to about 20° F.
Agave weberi
This agave is
often seen in the southwestern United States and parts of Mexico,
but only in cultivation as there does not appear to be any wild
specimens left. This is a potentially large plant that may
reach 5 feet in height and up to 10 feet across. The grey-green
leaves have fine teeth along the margin of the lower end of the leaf
and a sharp terminal spine. The flower spike is branched and
contains yellow flowers and occasionally bulbils as well.
Plants require full sun to part shade to look their best.
Yellowing of the foliage may indicate heat stress and a requirement
for more water. Hardy to 12° F.
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