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Plant Highlight: ×Mangave ‘Silver Fox’
By Brian Kemble
Taxonomic placement
The genus Agave contains many species with large rosettes of tough fibrous leaves, with surprisingly tall flower stalks, commonly known as century plants. However, there are related plants that have been moved in and out of the genus, considered by some to be “sister groups” with their own genus names, and included by others within Agave. A prominent example is Manfreda, first recognized as a genus in 1866, but now considered by many authors to be a subgenus within Agave. When considered as a separate genus, a cross between a Manfreda and an Agave is known as a ×Mangave, with the multiplication sign at the beginning serving as an indication that it is not a true genus, but rather a hybrid between two genera, its name being a combination of the two actual genera involved. If Manfreda is treated as a subgenus within Agave, then the name would become simply Agave ‘Silver Fox’, but it is widely known in horticulture under the former name.
The reason for separating out Manfreda (and treating it as its own genus) lies in the appearance of the plants, since they have a bulb-like swelling at the base and soft pliable leaves. In some cases, they go completely deciduous during their period of dormancy. Many Manfreda species also have red, purple or maroon spots on their leaves, though this is not true for all of them. One of the reasons for making hybrids between a Manfreda and an Agave is the desire to come up with a plant that has the sculptural solidity of the latter, along with the purple spots that can be found in the former. Even when the purple spots are only faintly present, the plants may retain an attractive purplish tinge.
About the plant
×Mangave ‘Silver Fox’ is one of the ×Mangave crosses with only a faint trace of spotting, but it has a beautiful silvery-bluish leaf color with a hint of purple. It is a cross between ×Mangave ‘Blood Spot’, a compact plant with prominent purple spotting, and Agave pablocarrilloi, a larger bluish plant from the Mexican state of Colima. The resulting hybrid has rosettes of elegantly arching toothy-edged leaves, initially single-headed, but eventually offsetting to form a small clump of heads. The rosette diameter is up to about 1½ feet (46 cm), with the leaves widest about ⅓ of the way up, and tapering to a spine-tipped point. It should not be surprising that ×Mangave ‘Silver Fox’ looks more agave-like than most of the ×Mangave crosses seen in horticulture, since its parentage is ¾ Agave and only ¼ Manfreda.
About the flowers
Plants of ×Mangave ‘Silver Fox’ at the Ruth Bancroft Garden have flowered at various times of the year, so apparently it does not have a regular flowering schedule. When a rosette gets ready to flower, the central growing tip elongates and extends upward to make a tall and slender flower stalk, reaching a height of up to 9 feet. In the upper half or two-thirds, the stalk has short lateral branches bearing small clusters of flowers. The flowers resemble those of their parent Agave pablocarrilloi, with a slender cylindrical lower portion, where the ovary is located, and a cup-like upper portion, with the stamens and the pistils extending well beyond. The flower is green at the base, while the cup formed by the tepals is an orangey shade of yellow (note that the term “tepals” is used in place of “petals” for flowers without distinct and separate sepals and petals, as is the case with agaves and their relatives). The stamens and the pistil are yellow, as is the pollen held on the anthers at the tips of the stamens. The flowers are on the small side for an agave, with a length of just over an inch (2.6 cm) to the tepal tips, and about 1.6 inches (4 cm) to the tips of the stamens.
Plants in cultivation
×Mangave ‘Silver Fox’ is not a difficult plant to grow if provided with good drainage and watered occasionally during the summer months (this is important in Mediterranean=climate regions like California, where little or no rainfall comes in the summer). It does well in full sun or in dappled sun, and it can take overnight dips below freezing in the winter. However, temperatures below 27° F (-3° C) should be avoided, as well as sustained freezes.
