In the United States the species of Agave are commonly called "century plants" because of the mistaken belief that the plants only flower after they reach an age of 100 years. But in reality they normally flower after 10-20 years when growing under favorable conditions. When grown in cultivation, especially in pots, many species only attain half their normal size and rarely bloom.

Agaves are in the family Liliaceae. Some authors put them in the family Amaryllidaceae if the ovary is inferior or in the Liliaceae if the ovary is superior. Agave americana was the first described species by Linnaeus in 1753 and probably the first to flower in Europe in an Italian garden.

Agaves include some 200-250 species. Central Mexico is the center of diversity. Mexico has more than 125 species while the U.S. has only 15 species. The rest are distributed through Central America, Baja California and the Caribbean basin. Agave pumila is only a few inches across and weighs less than a pound while Agave atroviriens can weigh over 2 tons and be 24 feet across. Each leaf may weigh more than 100 lbs.

The Genus Agave is divided into two subgenera. Littaea has spicate inflorescences. Agave has paniculate inflorescences.
	spicate inflorescences	paniculate inflorescences

Howard Scott Gentry published a monograph on the agaves in 1982 based solidly on the floral characteristics. The flowers are perfect and tube-like. They have six stamens and six tepals (3 petals and 3 sepals that are hard to tell apart). There is a three parted style and a three celled ovary. In the flowers the stamens ripen first and after the pollen is released then the stigma elongates and is ready to receive pollen. The flowers are pollinated by insects, bats or birds. The fruit is a dry capsule that splits longitudinally to release many seeds.

Most agaves, but not all, are monocarpic; that is the individual rosettes die after flowering. But in a few, like Agave parviflora, the rosette lives on.

Agave leaves are hard or rigid with many fibers inside. Agave sisalana has very strong fibers and is grown in Tanzania, Indonesia, Brazil, and the Philippines for its fibers. The leaves of many have sharp teeth along the sides and almost all have a rigid, sharp terminal spine. There may be twenty to two hundred leaves in a rosette and they have special cells for water and food storage. Leaf color ranges from a bright green to dull gray-blue. Leaves live 12-15 years, often the entire life of the plant. All of the water storage and energy storage of the plant is in the leaves.

The stems of agaves are usually short, but rhizomes are common and buds along the rhizomes form colonies. Agave roots are fibrous in nature and new roots form very quickly after a rainfall.

Bloom stalks may range from six feet in small species to more than forty feet in large ones. Flowering occurs from bottom to top and may last for two months. The flowers, which are very rich in nectar and pollen, are pollinated by hummingbirds, other birds, bats, bees, moths and other insects. Musky smelling flowers probably attract bats, while sweet smelling flowers attract the insects.

Agaves grow where temperatures regularly exceed 106^o Fahrenheit and where winter lows reach -15^o Fahrenheit. They occur from sea level to mountains over 8,000 feet.

Agaves were used as a food source as long ago as 1,000 AD. They were grown on terraced hillsides. The leaves were cut away and the large heads were placed in roasting pits. The buds and flowers of agaves can also be eaten raw or cooked. Agaves were outranked as important plants by the Aztecs, Mayans and other Indians of Mexico only by corn and potatoes. Agaves have been used for: food, drink, soap, clothing, rope and other fibers, needles and thread, paper, glue, weapons, military instruments, medicines, red coloring matter, forage, and ornamental and hedge plants.

Pulque, a mildly alcoholic beverage, is made from agaves, principally A. salmiana, A. mapisaga, A. atrovirens, A. hookeri and A. americana. Mescal is a distilled agave beverage. Tequila is mescal made in the state of Jalisco near the town of Tequila. By law that's the only mescal that can be called tequila.

Agave plants propagate by seeds, offsets or suckers and by bulbils. A particular species may propagate by one, two or all three methods.

The agaves have a relatively small root system and do well in containers. The soil should not be too rich and should have excellent drainage. Agaves should be planted a little high with all leaves above the lip of the container. Agaves can be slightly under potted to keep them smaller. Agave roots can be trimmed before (re) potting and allowed to dry for a few days. Or they can be planted in a dry mix and watered a week later. Container grown plants are about half the size of plants grown in the ground. Potted agaves can be grown in partial shade as the pots dry out more quickly. They should be grown quite dry in the winter.

Agaves are easily grown from seed which remains viable for up to five years or longer if frozen. Seeds germinate in one to three weeks. Germination is faster at warmer temperatures, above 80^o Fahrenheit. Seedlings should be grown in strong but indirect light. It should be noted that agave species hybridize very easily and it can be very difficult determining if the seed is pure.

Pests of agaves include rabbits and other rodents. The agave snout weevil, a one inch black insect, lays eggs at the base of a leaf, usually once the plant is getting ready to bloom. A sudden wilting of leaves is usually the first sign of infection. Fungal infections caused by wet weather or over watering can also occur. Fungicides will usually correct this problem if watering is reduced.

• A. cerulata 10^o F
• A. havardiana -10^o F
• A. lechuguilla O^o F
• A. lophantha 10^o F
• A. murpheyi 10^o F
• A. neomexicana -20^o F
• A. palmeri 10^o F
• A. parryi -20^o F
• A. parryi var. couesii O^o F
• A. parviflora 10^o F
• A. salmiana 5^o F
• A. scabra 10^o F
• A. schottii 10^o F
• A. toumeyana 10^o F
• A. utahensis -10^o F
• A. utahensis var. eborispina -10^o F
• A. utahensis var. kaibabensis -10^o F
• A. utahensis var. nevadensis O^o F
• A. victoriae-reginae 10^o F
• A. weberi 12^o F

The genus Yucca consists of some 50 species and Mexico with 30 species is a center of yucca diversity. The United States yuccas range from the Atlantic to the Pacific Oceans and north into the Canadian prairie provinces.

In the colder, northern parts of their range, yucca species tend to be small and trunkless; but in the warmer and tropical areas, some species may become many branched trees up to 30 feet high.

Yucca leaves can be rigid, pliable or even lax. The leaf end may bear a sharp or blunt spine or no spine at all. About half the species have marginal filaments which may be colored brown, yellow or white.

The bell-like flowers of yuccas have three sepals and three petals that are so similar that they are refered to as tepals. Tepals vary in color from greenish white to creamy white or clear white and they are thick and leathery.

Yucca ovaries are superior with three chambers that contain many ovules. This is common in the lily family. The six stamens are shorter than the three styles. Different species of white moths in the genus Pronuba are responsible for the pollination of yucca flowers. The female Pronumba collects a ball of pollen and flies to another yucca flower where she james the pollen down the pistil. But before she leaves, she lays a few eggs in the ovary where the larvae develop by eating some, but no all, of the maturing seeds. This is an example of mutualism, where each species depends on the other for its survival.

About half the yucca species have woody capsules similar to agaves, while the other half have fruits that are large and fleshy. These are eaten by native peoples and by many animals.

Agave parryi is one of the hardiest century plants. It will tolerate temperatures down to -20^o F. It grows from central Arizona down into the Mexican states of Durango and Chihuahua at elevations of 1500 to 8000 feet. This agave forms a tight, round rosette of light gray to blue-green leaves 12-20 inches tall and up to 29 inches wide, Rosettes may be solitary or form extensive colonies. The flowering spike grows up to 20 feet with 18-30 branches. Flowers are a bright lemon yellow with a touch of red or pink. Flowering occurs from June to August.

Agave utahensis grows further north than any other agave, reaching Utah and Nevada. It can withstand temperatures of -10^o F. for long periods of time. This small plant grows up to 12 inches tall and 16 inches wide. The gray-green leaves are 1 1/4 inches wide. A terminal spine may be 1 1/2 inches long or in some varieties even longer. The flower spike reaches 8 feet and the light yellow flowers are usually seen in May or June.

Yucca baccata is commonly called the banana yucca as the large fleshy fruits were an important source of food for many native peoples, being eaten either raw or roasted. This yucca grows over a wide range in the southwestern U.S. and northern Mexico. It is hardy down to -20^o F. The concave leaves vary in color from blue-green, gray-green to even a light blue-gray. They grow up to 2 1/2 feet long and are 2 1/4 inches wide. Most of the flowering panicle is buried within the head of leaves. The cream colored flowers, which are often striped in purple, hang down and only open at the tip.

Yucca harrimaniae can be as small as 5 inches or up to 22 inches tall. Single rosettes may reach 36 inches in diameter and it often grows in large clumps. Leaves range from 4 to 18 inches long and are 1/2 inch wide, rigid and bluish green. White filaments twist from the leaf margins. The flowering raceme may reach 3 feet and the flowers are greenish white. Found in the mountains and high plateaus of the Southwest up to 8500 feet, this yucca is cold hardy down to -20^o F.

Yucca brevifolia is called the Joshua Tree. This is a characteristic plant of the Mojave Desert and the primary reason why Joshua Tree National Park was created. Joshua Trees can grow to 30 feet with an equal spread. The rigid, gray-green leaves from 6-14 inches long and 1/2 inch wide are clustered tightly at the ends of the many branches. The cream to greenish-white flowers are in dense panicles at the ends of the branches. They only open at the tip and have a slightly unpleasant odor. Yucca brevifolia has proved hardy to -10^o F in Denver.

Yucca glauca, the Plains Soapweed, is probably the most cold hardy of all the yuccas. It grows as far north as Alberta and Saskatchewan, Canada. The very narrow leaves range from 1/4 to 1/2 inch in width and 8-36 inches in length. Leaves are gray-green in color and have filaments from the white marginal stripes. The greenish-white flowers are fragrant and pendulous. They occur in a dense spike up to 6 feet tall.

The Chinle Cactus and Succulent Club