Introduction to the Furcraeas, the giant Agave Look-alikes
For years I have been fascinated by Agaves and have grown hundreds of them in my yard. But on one of my trips to an arboretum, I saw some huge plants I thought were Agaves, and I was surprised to find that these were NOT agaves, but members of a related genus called Furcraea. For those who are as confused as I was, here's another interesting twist. One of the common names for Furcraea in the nursery trade is "century plant," a name often associated with some of the Agaves, which just adds to the confusion. I never understood the reason for this common name, as neither Agaves nor Furcraeas live anywhere near a hundred years.
But Furcraeas are indeed a separate genus, differentiated biologically primarily by their distinct flower shape (bulbous versus filiform). I never cease to be amazed at the little things that can keep two very similar plants from being closely related. In general, Furcraeas are New World members of the family Agavaceae and are basically large Agaves (though there are a few Agaves larger than the largest Furcraeas.) They are non-suckering rosette plants with thick, stiff, succulent leaves. Some form tall stems while others remain stemless. Some have armed leaves (like many Agaves) while others have smooth, ‘user-friendly' leaves. Some are variegated (though I don't know if that is a completely ‘manufactured' look or if plants in the wild are similarly variegated). Like most Agaves, Furcraeas are monocarpic. However since they do not sucker, this is their only shot at passing on their genetic materials so they do it quite flamboyantly. Furcraea inflorescences are very tall (up to 40 feet in some species) and produce hundreds if not thousands of bulbils, on thin branches, which fall to the ground and root--that's the strategy, at least.
Furcraea foetida 'Mediopicta' flowering unopened flowers flowers
bulbils on Furcraea selloa and Furcraea permentieri (photo Jay9)
Bulbil photos (second photo by cactus-lover)
Wikipedia lists dozens of species of Furcraea, but only a handful are common in cultivation. It's those species that will be briefly covered in this article.
Furcraea foetida (Mauritius hemp) This is probably the most common Furcraea in cultivation partly due to is economic important as a source of hemp fiber (grown in massive quantities on the island of Mauritius, though this is originally a South American species) and partly due the plant being a fairly user-friendly as well as beautiful and manageable in the landscape. The variegated forms (primarily one called 'Mediopicta', but there are striped and marginate forms as well) of this species are far more common than the plain green forms, thanks to their excellent ornamental appeal. As mentioned this is a ‘safe' species with no sharp edges to speak of. It is a stemless to short-stemmed species forming a many-leaved clump about 4 feet by 4 feet. It has moderate cold hardiness into the mid- to high- 20s F. Claims of Furcraea foetida surviving temps below 20 F exist... I just doubt them. This species is happy in a large variety of climates, from hot arid to moist tropical. Furcraea gigantea is a synonym.
Furcraea foetida 'Mediopictas'
Furcraea foetidas (first photo by Monocromatico)
Furcraea selloa (wild sisal) is probably the next most commonly grown species in cultivation and is a much larger and less friendly plant, best used in wide open spaces or far from walkways. This plant has long stiff leaves (up to 5 feet) that tend to widen near the tip before narrowing to a sharp, stiff point (creating a sort of spoon shape with a needle at the end). The leaf margins are heavily armed with very sharp teeth. As is the case with Furcraea foetida, the variegated (marginate) form is by far the most commonly seen thanks to its superior ornamental value. This plant forms a stem eventually (though some individuals flower before this happens) and some plants can develop trunks up to 10 feet tall. The flowers of this species are exceptionally tall and fairly sparsely branched.
Furcraea selloa with tall trunks Furcraea selloa 'Marginata' Furcraea selloa 'Marginata' with about 10 feet of trunk
leaf detail showing marginal teeth (photo by cactus_lover)
Furcraea macdougallii is not nearly as common as the two previously mentioned species, but it is my favorite of the available Furcraeas in cultivation. This is huge plant forming a large trunk fairly reliably and these trunks can grow over 20 feet tall (I have not seen any taller.) The leaves are narrow, deep blue-green and have soft marginal teeth. The texture of the leaves is rough like shark skin. Young plants tend to have an upright habit with only the very oldest leaves protruding laterally. But as plants age, the effect matures to form a silhouette of a pine tree or possibly a Phoenix palm. Large older specimens are imposing plants indeed. This is a moderately user-friendly species with few dangerous sharp edges. This plant is cold hardy down to the mid-20s and prefers full sun in very warm arid conditions.
Furcaea macdougalliis, young potted, maturing but still no trunk, and older, trunking plant
clump of plants in Los Angeles (not suckering, but planted nearly on top of each other); second photo shows close up of leaf bases; third shows plant that has flowered and all leaves gone now
The only other species I have come across in cultivation (though there may be more, of course) is Furcraea roezlii. This is another blue-green-leaved species but these leaves are flatter and much wider like the two first Furcraeas discussed. Furcraea bedinghausii may be the same species but tends to be a larger, longer-leaved version. These plants are stem-formers and older plants tend to keep petticoats of old dead leaves nearly the entire length of the trunks.
Furcraea bedinghausiis (behind Agaves in first photo, and beside a Yucca in second)