Century Plant (Agave)

Agave is a long-leaved succulent plant that naturally forms a rosette shape and produces a flower spire of attractive cup shaped blooms. The plant is drought tolerant and perennial, making it ideal for the mature arid garden. Many agave plants are native to North America and are adaptable to colder climates in the Pacific Northwest and even Canada.

I. Appearance and Characteristics 

Agave (; ; Anglo-Hispanic, ) is a genus of monocots native to the arid regions of the Americas. The genus is primarily known for its succulent and xerophytic species that typically form large rosettes of strong, fleshy leaves. Agave now includes species formerly placed in a number of other genera, such as Manfreda, ×Mangave, Polianthes and Prochnyanthes.

Many plants in this genus may be considered perennial, because they require several to many years to mature and flower. However, most Agave species are more accurately described as monocarpic rosettes or multi annuals, since each individual rosette flowers only once and then dies; a small number of Agave species are polycarpic.

The succulent leaves of most Agave species have sharp marginal teeth, an extremely sharp terminal spine, and are very fibrous inside. The stout stem is usually extremely short, which may make the plant appear as though it is stemless.

Agave rosettes are mostly monocarpic, though some species are polycarpic. During flowering, a tall stem or “mast” (“quiote” in Mexico), which can grow to be 12 meters (40 feet) high, grows apically from the center of the rosette and bears a large number of short, tubular flowers and sometimes vegetatively produced bulbils (a form of asexual reproduction). After pollination/fertilization and subsequent fruit development, in monocarpic species, the original rosette dies. 

However, throughout the lifetime of many Agave species, rhizomatous suckers develop above the roots at the base of the rosette. These suckers go on to form new plants after the original rosette desiccates and dies. Not all agaves produce suckers throughout their lifetimes; some species rarely or never produce suckers, while others may only develop suckers after final maturation with inflorescence. Some varieties can live for 60 years before flowering.

Agaves can be confused with cacti, aloes, or stonecrops, but although these plants all share similar morphological adaptations to arid environments (e.g. succulence), each group belongs to a different plant family and probably experienced convergent evolution. Further, cactus (Cactaceae) and stonecrop (Crassulaceae) lineages are eudicots, while aloes (Asphodelaceae) and agaves (Asparagaceae) are monocots.

Adaptations

The agave root system, consisting of a network of shallow rhizomes, allows the agave to efficiently capture moisture from rain, condensation, and dew. In addition to growing from seeds, most agaves produce ‘pups’ – young plants from runners. Agave vilmoriniana (the octopus agave) produces hundreds of pups on its bloom stalk. Agave leaves store the plant’s water and are crucial to its continued existence. The coated leaf surface prevents evaporation. The leaves also have sharp, spiked edges. The spikes discourage predators from eating the plant or using it as a source of water and are so tough that ancient peoples used them for sewing needles. The sap is acidic. Some agaves bloom at a height up to 9 m (30 ft) so that they are far out of reach to animals that might attack them. Smaller species, such as Agave lechuguilla, have smaller bloom stalks.

II. How to Grow and Care

Sunlight

Agave plants prefer a spot with full sun, meaning at least six hours of direct sunlight on most days. But they can tolerate a little shade. The hotter the climate is, the more shade they can handle.

Temperature and Humidity

Most agave plants can’t tolerate frost and can only grow as far north as USDA growing zones 8 or 9. But some, such as Agave parryi, are reliably perennial to zone 5. Moreover, most agaves prefer a climate with low humidity. High humidity can lead to crown rot on the plant

Watering

Because agaves store moisture in their leaves, they don’t need large amounts of it to survive and are more likely to die from too much of it rather than too little. In summer, water them no more than once per week, cutting back to no more than once every 2 or 3 weeks in winter. Of course, If Mother Nature provides water through rainfall, you won’t have to. If she provides too much water in your climate, so that the agaves rot, consider placing them in raised beds, on mounds, or in containers for better drainage.

Agaves growing in containers need regular and sufficient watering. However, always check to make sure the container’s mix is at least half-dry before giving it more water.

Soil

Agave plants tolerate any well-draining soil but prefer rocky or sandy soil. Poor soil drainage can lead to root rot, killing a plant. Moreover, they like a slightly acidic to neutral soil pH.

Fertilizing

Because they originated in “poor” soil, agaves don’t need many nutrients to survive, and some gardeners don’t fertilize them at all. If you prefer to do so, use a type of plant food intended for cacti and succulents such as 1-2-2, in which the first (nitrogen) number of the ratio generally is smaller than the last two. If you prefer to use a balanced all-purpose fertilizer such as 10-10-10, apply only about a fourth of the amount recommended once in early summer.

Fertilizing agave might force it to bloom sooner, so keep that in mind. If you fertilize an agave, only do so during its growing season, not in winter. Container-grown agaves might benefit more from fertilizer.

Propagation

Mature agave plants produce pups, or tiny new plants, around their base. They can be propagated from these pups. Not only is this an inexpensive way to get new plants, but it also prevents the mature plant from becoming overcrowded by young plants. The pups generally can be propagated at any time, but it’s best to wait until they’re a few inches in diameter. Here’s how:

• Loosen the soil around the pup to find the root connecting it to the parent plant. Cut that root with a sharp trowel, be careful not to cut any roots growing from the pup.
• Gently dig up the pup, leaving as many of its roots as possible intact.
• Place the pup in a shaded, ventilated area for a few days, so the root you cut can form a callus.
• Using succulent potting mix, plant the pup in a small container with drainage holes. Lightly moisten the soil, and place the container in a bright, warm spot.
• Continue to water when the top inch of soil dries out, but don’t saturate the soil. The pup should be ready for transplanting outside in a few weeks if you wish. 

Potting and Transplanting 

As with many succulent plants, many agave species have shallow roots. So you can grow them in a shallow container because they don’t need much soil. Just make sure the container is sturdy and can anchor the weight of the plant. An unglazed clay pot is ideal because it will allow excess soil moisture to evaporate through its walls. Also, make sure the container has ample drainage holes.

Use a well-draining potting mix made for succulents. Water the container about once a week in the summer and monthly in the winter. Wait until the soil is dry a few inches down before watering.

Plan to repot or transplant your agave plant every few years as it matures. The best time is in the spring or summer. Use a slightly larger container and fresh potting mix. Once it’s mature, you can leave the plant in the same container, but plan to refresh the potting mix every couple of years.

Pests and Diseases

Agaves commonly suffer from crown rot due to an overabundance of moisture collecting inside their rosettes of leaves. To prevent this, grow them in a very well-draining location and water the plants from the side to avoid pouring water directly into the rosettes.

The plants also attract inch-long black agave weevils, which chew holes in the agaves to lay their eggs there, introducing a bacterial rot exacerbated by larvae digging deeper into the foliage. Dispose of all affected plants. You could also try applying an organic insecticide that kills grubs in the soil.

III. Overwintering Agave Plants

Gardeners growing agaves in pots likely will want to bring them indoors over winter to protect them either from freezing temperatures or too much precipitation.

When is the best time to bring agave indoors?

In zones where agaves aren’t hardy, bring them indoors before your first fall frost. Although some tolerate mild frosts, freezing temperatures may turn the more tender types—such as the foxtail agave—to mush. Others, such as the artichoke agave, can survive temperatures below zero, but usually only in dry climates.

How do you overwinter agave?

Don’t fertilize your agave during fall or winter. Plants growing outdoors might need a blanket or thermal wrap if temperatures dip below normal lows for the region. For wintering agave indoors:

• Place your plant next to a south-facing window where it will receive at least 5 hours of sunlight per day.
• If possible, choose a cool site where the temperature remains between 50 and 60 degrees all winter.
• Allow the plant’s soil to dry out completely before you water it again.
• Rotate the pot a half turn (180 degrees) about once every 2 weeks to keep the plant growing upright rather than leaning toward the light

IV. Uses and Benefits 

• Food and fiber

Each agave plant produces several pounds of edible flowers during its final season. The stalks, which are ready during the summer, before the blossom, weigh several pounds each. Roasted, they are sweet and can be chewed to extract the sap or aguamiel, like sugarcane. When dried out, the stalks can be used to make didgeridoos. The leaves may be collected in winter and spring, when the plants are rich in sap, for eating. The leaves of several species also yield fiber, for instance, A. sisalana, the sisal hemp, and A. decipiens, the false sisal hemp. A. americana is the source of pita fiber, and is used as a fiber plant in Mexico, the West Indies, and southern Europe.

The agave, especially A. murpheyi, was a major food source for the prehistoric indigenous people of the Southwestern United States. The Hohokam of southern Arizona cultivated large areas of agave.

The Navajo similarly found many uses for the agave plant. A beverage is squeezed from the baked fibers, and the heads can be baked or boiled, pounded into flat sheets, sun dried, and stored for future use. The baked, dried heads are also boiled and made into an edible paste, eaten whole, or made into soup. The leaves are boiled, and the young, tender flowering stalks and shoots are roasted and eaten as well. The fibers are used to make rope, the leaves are used to line baking pits, and the sharp-pointed leaf tips are used to make basketry awls.

During the development of the inflorescence, sap rushes to the base of the young flower stalk. Agave syrup (commonly called agave nectar), a sweetener derived from the sap, is used as an alternative to sugar in cooking, and can be added to breakfast cereals as a binding agent. Extracts from agave leaves are under preliminary research for their potential use as food additives.

• Beverages and tequila

The sap of A. americana and other species is used in Mexico and Mesoamerica to produce pulque, an alcoholic beverage. The flower shoot is cut out and the sap collected and subsequently fermented. By distillation, a spirit called mezcal is prepared; one of the best-known forms of mezcal is tequila. A. tequilana or A. tequilana var. azul is used in the production of tequila. A. angustifolia is widely used in the production of mezcal and pulque, though at least 10 other Agave species are also known to be used for this.

• Research

Agave can be used as the raw material for industrial production of fructans as a prebiotic dietary fiber. Agave contains fructooligosaccharides, which are naturally occurring oligosaccharides that support safely subjecting peanut-allergic people to allergen immunotherapy. Resulting from its natural habitat in stressful environments, agave is under preliminary research for its potential use in germplasm conservation and in biotechnology to better anticipate the economic effects of global climate change. It may also have use as a bioethanol or bioenergy feedstock.