Spiny Redberry

Spiny redberry (Rhamnus crocea) is a small to medium, evergreen shrub native to coastal California and northern Baja California. It is often found found in valleys and canyons within the coastal sage scrub and chaparral. The smaller branches are short and stiff and pointed on the ends, giving the plant part of its name. Inconspicuous flowers are followed by bright red berries, which are quickly devoured by birds.

Several widely separated plants grow along the Rios trail. The best time to see them is in early summer when the red berries shine out against the bright green leaves.

Redberry is the only host plant for the Hermes copper butterfly, one of the rarest butterflies in Southern California. To date, we have found no Hermes coppers in the Reserve.

Description ^2,4,11,59

Spiny redberry is an evergreen shrub that is usually less than six feet (2 m) in height, although shrubs to 10 feet (3½ m) have been reported. The shrub is dense, with many short, stiff branches. The smallest branches are reddish, often sparsely leafed or leafless along the outer part and pointed at the end.

The small leaves are glossy and bright green, on short reddish petioles that are subtended by two inconspicuous stipules. Leaves are ovate or obovate, usually less than 3/4 inch (1.8 cm) in length. The margins are entire or sharply toothed. The midvein is prominent on the lower surface and depressed on the upper surface.

The tiny flowers, less than 3/16 inch (4.5 cm) across, occur in small inconspicuous clusters along young branches. Petals are absent, and the four spreading, triangular sepals resemble petals. Sepals are cream-colored, sometimes edged or tipped with red-brown. Flowers are usually (but not always) functionally male or female and the male and female flowers are usually (but not always) found on different plants. A male flower has four pollen-producing stamens that stand erect and alternate with the sepals and a vestigial pistil. The female flower is generally similar in appearance to the male, but it is slightly smaller, with narrower sepals and a more rounded base. There is a functional pistil with a two-chambered ovary and a style that is forked at its midpoint. Four rudimentary stamens are present. Spiny redberry blooms mainly in Feb. and May.¹

In spite of the common name, the conspicuous fruit is not technically a berry, but a “drupe” like the fruit of a plum or cherry. A drupe is characterized by a fleshy exterior layer usually surrounding a single seed, which is enclosed in a hard, leathery wall. The ripe spiny redberry fruit is spherical, about 1/4 inch (0.6 cm) in diameter and bright red, and there may be two seeds in each drupe.

Classification  

Spiny redberry is a dicot angiosperm in the buckthorn family (Rhamnaceae),² a large family with a worldwide distribution,⁴⁴ but most common in tropical and subtropical habitats.⁴¹ Species in this family are usually many-branched shrubs or trees with tiny four or five-petaled flowers clustered at the ends of branches. Stamens arise from the bases of the petals. Undivided leaves are subtended by stipules which may be conspicuous.

In California, the largest and best-known genus in this family is Ceanothus, the genus of our wild lilacs.⁷

We have three species of buckthorns in the Reserve.⁴⁸ The others are wart-stemmed ceanothus (Ceanothus verrucosus) and the rare California spinebush (Adolphia californica).

Subspecies have been described for spiny redberry,^41,67 but none are currently recognized in California, pending further study.²

Ecology  

Numerous birds are attracted to the fruit of spiny redberry.^59,290 Especially mentioned are Western Bluebirds²⁴ and Mockingbirds.²⁷² Birds are an important dispersal mechanism, but spiny redberries (and other plants in the same genus) have a unique two-staged dispersal procedure.¹¹ Each seed within the fleshy outer layer of the fruit is enclosed in a leathery seed coat, which is not digested by the avian consumer, but is instead regurgitated to land on the ground beneath – presumably along with the remains of the rest of the fruity meal. Once the rejected bit dries, the seed coat opens explosively, propelling the seed away from the original dumping ground and spreading out potential seedlings.

Human Uses  

The Chumash, of central California, used the roots of spiny redberry to make a yellow dye for buckskin.³⁶⁰

Given the conspicuous and tasty-looking berries, it is surprising that there are not more reports of consumption by native Americans. I found one brief mention that three geographically scattered California tribes “and others” ate the berries fresh during the summer.⁷⁵  Another study mentions berry consumption by the Kumeyaay of Baja California.²⁷² Our local Kumeyaay reportedly used the berries as pet food, feeding them to mockingbirds, which were kept for their song.¹⁶

Interesting Facts  

Spiny redberry is the only host of the Hermes copper butterfly (Lycaena hermes), a “fascinating little sprite”³⁸² and one of the rarest butterflies in San Diego. The Hermes copper is a small, quick butterfly that is patterned with brown and orange and yellow.¹¹⁶Although spiny redberry is widely distributed in coastal California, for reasons unknown, the Hermes copper is restricted to a very small area in western San Diego County and adjacent Baja California. These populations have been fragmented and isolated from each other by development, and individual populations are seriously threatened by wildfires.^382,383

The Hermes copper is listed as “Vulnerable” by the IUCN,¹⁷² as “Critically Imperiled” by NatureServe,¹¹³ and, as of 2018, it is a candidate for federal listing as threatened or endangered.³⁸³

Hermes coppers have not been reported from the Reserve.¹⁰⁰ Perhaps our present spiny redberry shrubs are too few and too isolated to support a butterfly population.