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Plant Highlight: Agave microceps
By Brian Kemble
Taxonomic placement
When Howard Scott Gentry published his monograph Agaves of Continental North America in 1982, he placed the various species in informal groups, rather than in formal sections. One of the groups was called the Filiferae, and it included Agave filifera along with its closest relatives. In 2019, formal sections were designated for the genus, and the plants in Gentry’s group Filiferae were placed in the section Littaea (not to be confused with the much larger subgenus Littaea, which includes many sections, including the section Littaea). One of the other species included in the section Littaea is Agave microceps, first named Agave filifera subspecies microceps by Myron Kimnach in 1995. It was later raised to the level of a species in 2007. Because it had not yet been discovered and described in 1982, it is not mentioned in Gentry’s book. Although it is related to the widely grown Agave filifera, and to its close relative Agave schidigera, Agave microceps is a smaller plant with a much more slender flower stalk, and it makes sense to treat it as a distinct species.
Area of occurrence
Agave microceps was first described from plants growing in the south-central part of Sinaloa, on the west coast of Mexico. At this locality, the population is only about 1600 feet (500 m) above sea level, growing on rocky low hills not far inland from the Gulf of California. Though this habitat is a little north of the Tropic of Cancer, the climate is quite tropical and temperatures never get anywhere near freezing in winter. It was quite surprising when a second locality was found for the species in a very different habitat to the south, in the state of Nayarit and at a much higher elevation. Here the plants were growing in a mixed pine-oak-madrone woodland setting at 6900 feet (2100 m).
About the plant
This is an offsetting species, making clusters of a few to many heads, with large cumps attaining a diameter of up to 40 inches or more (1 m). Each head is from 9½ to 16 inches across at maturity (24 to 40 cm). The sharp-tipped sword-like leaves are 4¾ to 8 inches long (12 to 20 cm), deep green in color, but often with a pale green stripe down the center of the upper surface. Sometimes there are a few white streaks on the leaf face, as seen also on plants of the related Agave schidigera. With more exposure to sun, the leaves may show a purplish or reddish tinge (especially the outer leaves). There is a narrow light gray fibrous strip along the leaf margins, and this frays to make curling threads which can be quite decorative. On new leaves, the upper part of the marginal strips, and the sharp point at the tip where they meet, can be orange to brown, but this coloration does not persist for long.
About the flowers
In habitat, Agave microceps is reported to flower mainly in spring to summer, but plants in cultivation do not hold to a consistent pattern. At the Ruth Bancroft Garden, we have had it flower in the winter and in the fall. The inflorescence is short for an agave, with a height of 40 to 53 inches listed in the original description (plants in cultivation can exceed this; an inflorescence at the Ruth Bancroft Garden was measured at 9 ft, or 2.75 m). As is true of other plants in the subgenus Littaea, this species lacks evident floral branches, though the flowers come in pairs along the stalk, and these pairs are essentially much-reduced branches, so it would not be correct to refer to the inflorescence as spicate. The flowers are on the small side, with a length of 2 to 2.17 inches (50 to 55 mm). The flower bud (and the outside of the open flower) has a basic color of light green to greenish-yellow, but this is often overlain by a tinge of mauve-gray. The tepals* spread widely and curl back when the flower opens, so that the pale yellow of the flower’s inside is on full display. Sometimes this yellow color is tinged purple. Extending out from the mouth of the flower are the 6 stamens, with pinkish to purple filaments and bright yellow pollen-bearing anthers. At the middle of the stamens is the pistil, with its sticky tip (the stigma) ready to receive pollen from a visiting pollinator. The style (the shaft of the pistil) may be greenish or purple.
About the fruits and seeds
After being pollinated, the ovary at the gase of the flower expands to become an elliptical green seed capsule, with 3 chambers holding stacks of small black seeds. At maturity, the capsule dries and turns brown, splitting open to release the seed. The seeds are semicircular and flattened, with a length of about .16 inch (4 mm) or a little more.
*This term is used in place of petals for flowers that do not have a clear distiction between sepals and petals.
Last 2 photos were taken in habitat.
