One of the most commonly seen succulents here in the tropics are the agaves, which are often used in landscaping. The symmetrical rosettes of spiny leaves give them an ornamental architectural appearance in the garden. There are about 200 to 250 or so species of agaves, all of which originally come from North America (mainly the United States and Mexico), Central America and the West Indies. Aside from being ornamental plants, agaves have many uses. The fibers obtained from Agave sisalana are used for weaving mats while the alcoholic drinks mescal, pulque and the famous tequila are all derived from agaves.
Agaves are quite easy to identify – they can easily be distinguished by their low rosettes of spiny fibrous leaves (as opposed to the very succulent leaves of the aloes which are not fibrous at all and break easily) and they come in a variety of sizes – from rosettes of about one to two meters in diameter to miniature species with rosettes of about one or two inches in diameter. Individual leaves of the agaves can be wide or thin, "painted" in white stripes like in Agave victoria-reginae and Agave parviflora or plain green as in Agave bovicornuta or grayish blue green as in Agave potatorum and Agave parryi. The margins of the leaves can have large tortuous spines as in some forms of Agave potatorum or fibrous filaments as in Agave filifera and Agave toumeyana, while some species like Agave bracteosa are virtually spineless.
Growing agaves in the tropics is quite easy. They are one of the few succulents that can tolerate much watering as long as the medium used to plant them in is well-drained and porous. A mixture of garden soil, well-rotted compost and sharp sand is a good medium to start with. Regular feeding with a mild fertilizer is recommended as most agaves are heavy feeders. A bright and sunny position will bring out the real beauty of these plants, making them grow into very compact rosettes. This is especially true for plants with bluish grey leaves such as Agave titanota, Agave potatorum, Agave patonii, Agave pygmae and the like. Given the right growing conditions, agaves rarely get any pests and diseases. Some of the more sensitive types, such as Agave victoria reginae, rot or produce unsightly brown spots on their leaves when overwatered.
Agaves are usually propagated from offsets or seeds. Many agaves usually produce offsets which can be removed when they are sufficiently large enough and potted individually. Unfortunately, the agave plant usually dies after flowering and producing seeds – this may take several years as the plant grows and stores energy reserves to produce its flowers. Some nurserymen usually cut off the flowering stalk when it emerges from the plant to divert the plant’s energies to produce offsets rather than flowers before it dies.
As most large agaves, such as Agave franzosinii, Agave angustifolia, Agave salmiana, Agave americana, etc., are used in garden landscaping, the smaller agaves can easily be grown to adult size in containers. Some of the choicest plants for succulent collectors are the medium and small-sized agaves such as the following:
• Agave victoria-reginae and the related A.fernandi-regis are named after Queen Victoria and King Ferdinand, and are quite slow-growing. When grown well, they produce beautiful tight rosettes, with each leaf having prominent white markings. Variegated versions of these plants are even more slow-growing, owing to the lack of chlorophyll in large parts of the leaves, thus limiting the plant’s ability to produce food and energy for its growth.
• Agave americana var. mediopicta is a beautiful and elegant-looking variegated plant which can grow quite large. It has a yellowish white stripe running along the center of the leaves, from the base to the tip. The white striped version is named var. mediopicta alba. There are also other variegated versions of Agave americana, such as the var. marginata which has variegations along the sides of the leaves and the var. striata which has more or less irregular variegations along the entire length of the leaves.
Agave potatorum and its varieties are one of the more sought-after agaves by collectors. The plant has powdery bluish grey leaves with black, brown or red spines, depending on the variety. Spines may also range from small and fine to thick and tortuous. Small varieties such as Shoji-Raijin and Kichiokan originating from Japan are beautiful compact plants that stay small. Variegated varieties of Agave potatorum are rare and hard to come by.
Agave patonii looks rather similar to A. potatorum. However, the leaves of the young plants recurve whereas in A. potatorum, the leaves are more or less straight or incurved. Adult plants of A. patonii make very beautiful symmetrical compact rosettes when grown well. This plant is a medium-sized agave and will make a beautiful landscape specimen provided it is protected from too much rain.
Another blue grey leafed plant is Agave parryi, which is also a very variable species. The spines of this plant are usually red colored when new and turn to buff brown when the leaves get older. These plants also form beautiful compact rosettes, especially the var. truncata which has shorter and wider leaves than those of the typical plant.
One of the smallest agaves is the Agave parviflora and the similar-looking A. toumeyana var. bella, which when grown well makes a sort of ball of numerous thin succulent leaves with prominent white markings and white frayed filaments along the edges of the leaves. These plants make very beautiful collector’s items when grown properly.
Agave filifera and the similar A. multifilifera are some of the more interesting varieties. As their names suggest, they have frayed filaments along the edges of their somewhat thin and long leaves. The leaves also have light white markings. A choice variety and one sought after by collectors is A. filifera var. compacta, a dwarf variety with short wide leaves that grows to only a few inches in diameter.
Agave pumila may perhaps be considered the smallest agave – in its juvenile stage, which may persist for many years, it is only about an inch in diameter with a few short and fat green leaves, very compact and succulent-looking. However, after many years, it may reach its adult phase and can grow much larger, reaching about 8 inches in diameter.
Another interesting agave is Agave nizandensis, which has a few fat succulent leaves that are dark green in color. Looking more like an aloe rather than an agave, the individual leaves of this plant have a pale stripe running along the length of its leaves.
Hybrid agaves can also be interesting. Agave x leopoldii, which is a hybrid derived from Agave schidigera and Agave filifera, is rather easy to grow. This plant has many long, thin leaves with curly frayed filaments along the leaf edges and faint white markings on the front and back of the leaves.
There are still many small- to medium-sized collectible species of agaves such as Agave stricta, especially the var. nana which is its dwarf variety, Agave colorata, Agave gemminiflora, Agave ocahui, Agave poliantheflora, and many others and their numerous varieties. The challenge for the collector is to find and grow these plants to perfection.