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Plant Highlight: Arctostaphylos refugioensis
by Brian Kemble
About the genus and area of occurrence
Arctostaphylos is a genus of shrubs (or sometimes small trees) in the family Ericaceae. This is a family well represented in horticulture, since it includes genera such as Erica (heath), Calluna (heather), Rhododendron, and Vaccinium (blueberry). While the family occurs around the world, the genus Arctostaphylos is mostly native to western North America, from Canada to Mexico, with the greatest concentration of species found in California. The exception is the most northerly species, Arctostaphylos uva-ursi, which is adapted to subarctic climates in the far north of Europe, Asia and North America. The common name for plants in the genus is manzanita, which means little apple in Spanish. This is a little confusing, because there is one widespread species In California whose botanical name is Arctostaphylos manzanita, but the common name manzanita is applied not only to this, but to all the other species as well. The various species of Arctostaphylos are found from the coast to the mountains, in a wide variety of habitats. One particular species, Arctostaphylos refugioensis, is endemic to Santa Barbara County in Southern California.
Arctostaphylos refugioensis occurs along the coast in places such as Refugio Beach, west of Santa Barbara, as well as in the Santa Ynez Mountains a little farther inland. Because of its very limited distribution, it is considered a vulnerable species.
About the plant
A. refugioensis is a well-branched shrub reaching a height of 6½ to 13 feet (2 to 4 m), or occasionally even more. The trunk and lower branches have the beautiful smooth reddish-brown appearance typical of the genus, while the newer twigs are light green and covered in long sticky hairs. The leaves are glaucous green, sometimes with a reddish rim or flushed red, and they are 1.2 to 1.8 inches long (3 to 4.5 cm). They may be oval in shape, with a pointed tip, but often the lower part of the leaf is more or less parallel-sided, imparting a boxy look. The petiole (leaf stalk) is very short or absent altogether, and there are rounded lobes at the base of the leaf on either side of the point of attachment; these can wrap around the branch and make it look almost as if the branch has perforated the lower part of the leaf. The margins may be smooth or have small teeth, and there are sometimes bristly hairs along the pale midrib. The two surfaces of the leaf look the same.
About the flowers and fruits
While A. refugioensis is generally winter-flowering, the timing varies from year to year. In an early year, our plants at the Ruth Bancroft Garden may finish flowering by the end of November, while in a late year, they may flower in January-February. As is usual in the genus, the inflorescences are multi-branched but short and compact, emerging at the tips of the branches with the small downward-pointing urn-shaped flowers bunched together. The dainty flowers are only about .32 to .4 inch long (8 to 10 mm), and they may be white or tinged with pink. The pedicels (the stalks of the individual flowers) are .28 to .35 inch long (7 to 9 mm), and covered with sticky bristly hairs like the branches from which they spring. The smooth shiny spherical fruits are .4 to .6 inch in diameter (10 to 15 mm) and red to reddish-brown at maturity, often with the persistent style jutting out from the tip like a wiry extension. The round red fruits bear a resemblance to miniature apples, and they are eaten by various mammals and birds. The seeds within are fused into a hard sphere, well adapted to passing unharmed through an animal’s digestive system.
Plants in cultivation
Although A. refugioensis grows relatively near the coast and does not often experience temperature extremes, it has proved quite adaptable in cultivation and can tolerate summer temperatures in excess of 100° F (38° C) as well as winter lows down to 10° F (-12° C). While it occurs on sandstone in nature, in soils with a neutral to slightly acidic pH, it is not picky as a garden subject and can be grown in a variety of soils if provided with good drainage. Once established, it needs very little water in summer, but occasional irrigation will not cause problems. Give it plenty of sun.
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