Coast Cholla

With its odd disjointed tree shape, cholla is an iconic image in the West, but it makes a poor hiking companion. The spiny terminal segments are easily detached by a passing boot or elbow and the spines secure the segments in place before the unwary hiker becomes aware. This activity has earned many species of cholla the name “Jumping Cholla.”

From the perspective of the cholla, spines are not a strategy of war, but an adaptation for reproduction and dispersal. When the spiny cholla hitchhiking segment becomes detached from its ride, it may be yards, or miles, from the parent plant. And even though weeks, even years may pass, when conditions are right, the wayward segment can sprout roots and become a new plant.

The flowers are a startling magenta, produced in the late spring on the terminal cactus segments. Oddly, these flowers rarely, if ever, produce fertile seeds, explaining, perhaps, cholla’s aggressive method of vegetative reproduction.

Description ^{2,4,59,96,554}

Coast cholla is a succulent plant, technically a shrub, up to 6-7 feet (2 m) high and often wider than high. One to several basal stems are ascending to erect and irregularly branched. The green outer stems are composed of cylindrical-sausage-shaped segments (joints) that are strongly constricted between segments. These segments are usually less than 12 inches (39 cm) long and 1.5 inches (4.3 cm) in diameter. The older stems are woody and lack conspicuous constrictions. Cholla surfaces are “bumpy” with helically arranged, oval elevations called tubercles.  Atop each tubercle is an “areole”, a highly modified bud that produces a cluster of spines. An areole may also produce a leaf, a flower and fruit or roots. Leaves are small, conical and short-lived.

Spines are of two types. There are five to twelve strong spines of various lengths, usually less than 1.5 inches (4.3 cm) in length, radiating outward. At their base is a small clump of tiny spines, “glochids”, < 0.10 inch (0.25 cm) long. The longer spines are barbless and strongly attached to the cactus pad. In contrast, the tiny glochids are armed with numerous barbs  and are easily detached, often in clumps. The glochids are clinging, irritating spines that easily penetrate the skin and are difficult to remove.

Conspicuous magenta flowers are sessile, usually less than 1.5 inches (4.3 cm) across, clustered at the tops of terminal segments. Flowers last one day. Sepals and petals are indistinguishable, collectively called tepals. Stamens are numerous, filaments grade from green to yellowish, turning magenta with age;  Anthers and pollen are yellow. The single pistil has an inferior ovary and one inverse-club-shaped style with usually, four pale greenish, stigmas exserted beyond anthers. Stamens are sensitive to touch and tilt inward when brushed. Major bloom period is late April through June.⁴⁶⁸

Flowers, and later fruits, may be produced from areoles of terminal segments or areoles of old fruit, leading to short lengths of two to five “chained” fruit. The fruit is a succulent, green sphere, with a flattened top covered with bark-like skin. Fruits bear tufts of glochids, but the long spines are generally fewer than on the stems, or they are lacking completely. The fruit of coast cholla is either seedless ^{59, 399} or produces seeds uncommonly. ^{96, 554}

Classification ^2,96,143,554

Coast cholla is a dicot angiosperm in the cactus family, Cactaceae, a family that has evolved in the New World.  Members of this family are characterized by succulent stems that contain chlorophyll and bear tufts of spines.

Species in the genus Cylindropuntia (cholla) were previously placed in the genus Opuntia (prickly pear). These two genera are distinguished from other cacti by the raised tubercles on the stems and the presence of glochids, tufts of very small, penetrating spines found at the base of the larger spines. Cholla are easily separated from prickly pears by their cylindrical stems and the occurrence of tubercles on stem surfaces.

Three cactus are presumed native to the Reserve: ⁴⁸  coast cholla, coast barrel cactus (Ferocactus viridescens), and western prickly pear, a hybrid swarm of Opuntia species. One other species of cholla, cane cholla (Cylindropuntia californica) has been planted in the revegetation area north of the Santa Carina trailhead. Cane cholla is most easily distinguished from coast cholla by its yellow flowers.⁵⁹

Ecology ⁹⁶

Coast cholla is one of a few chollas that has an extremely low rate of seed production ^{96, 554} – if it produces seeds at all. ^{59, 399}  One study of 100 coast cholla fruits, found only two seeds.⁵⁵⁴ Thus, its reproduction is limited to vegetative propagation. The terminal segments and old fruit are readily detached from the plant. With their internal store of water, these can survive detachment for weeks even years. Roots may form from the broken end, or even from the areoles.

In contrast to what most hikers think, the purpose of the “jumping” terminal segments may not be to deter hikers, but to hitchhike in the fur of passing animals, carrying the cholla propagule away from the parent plant. Sometimes the cholla passenger ends up in a favorable habitat and begins a new rooted plant, possibly a new population.

However, vegetative (asexual) propagation alone has evolutionary consequences. Since each offspring is identical to the parent, the development of genetic diversity within a population is curtailed. This is advantageous to a farmer or horticulturist, but  asexual reproduction is considered to be unfavorable for the long-term survival of a natural population. While many plants reproduce both sexually (through seeds) and vegetatively – a “covering your bets” strategy – very few reproduce only vegetatively (but see Bermuda buttercup).

The future of our coast cholla population is uncertain. The outcome of this strategy may be understood only with the passage of time.

Human Uses

Among numerous ethnobotanical references, virtually none mention the use of coast cholla by native Americans, although several species of cholla were used for food in other regions.²⁸²

Modern artisans, however, have found a rather unexpected use for this spiny plant. Most cactus species have an internal framework of wood in their perennial stems. Wood of cholla is cylindrical with an attractive pattern of lenticular spaces between “cables” of wood that reflects the surface arrangement of the tubercles.⁵⁵⁴ Modern artisans use skeletonized pieces of cactus, especially cholla and saguaro, for many things from sculptures, to jewelry to dried flower arrangements and aquarium decorations. ⁵⁴⁸

Skeptical? Try searching Google for “cactus wood”.

Interesting Facts

The Legend of a Gentle Rose and a Spiny Cholla ⁵⁵⁵

Once upon a time, gentle Rose had a birthday party and all the plants and animals were invited. Bird sang for her a beautiful song; Bee brought her tasty honey and Spider wove for her a silken scarf. But poor Cholla had nothing to bring and was very sad.

When it was Cholla’s turn to give a present, he shyly gave Rose the only thing he had – a cluster of his nastiest spines; perhaps they would  protect her delicate flowers. Rose was so touched with his thoughtfulness that she, in turn, gave Cholla a beautiful flower to liven up his spiny coat.

And so, to this day, Rose is defended by a spiny coat and Cholla brightens the world with lovely flowers.