Bladderpod

Bladderpod (Peritoma arborea) is a small but distinctive shrub native to Southern California, Baja California and northwestern Mexico. In spring it bears clusters of bright yellow flowers, which attract hummingbirds, butterflies and many types of bees. Flowers are followed by conspicuous leathery, inflated seed pods, which hang from the branch ends and give the plant its common name.

Bladderpod is a host of the colorful harlequin bug, which sucks sap from the flowers, pods and leaves. Look closely at a bladderpod and you will usually find one or a few of these black and orange bugs. Harlequin bugs can be serious pests on crop plants in the mustard family, particularly cabbage. Just what keeps them under control on bladderpod is an ecological puzzle, the subject of scientific research.

Description ^2,4,11,23,59

Bladderpod is a small, rounded evergreen shrub that grows to 10 feet (3 meters) high, but is usually much smaller. It is dense with pale, interwoven branches. Stems, leaves and fruit are covered with a waxy coating and contain strong smelling compounds,  mustard oils, produced from glucosinolates in the plant tissues when the tissues are damaged. These compounds, which give cabbage and broccoli their piquant flavor, give the bladderpod a disagreeable odor. The odor has been called sulfurous⁴ and compared to burned popcorn;¹⁶⁹ some detect a strong green pepper component.²⁷¹

The gray-green leaves are palmately divided into three leaflets less than 1 3/4 inches (4.5 cm) long. Leaves decrease in size toward the flowering end of the branches; those nearest the flowers are often undivided.

The showy flowers are bright yellow, up to 5/8 inch (1.6 cm) long and clustered at the branch ends. There are four green sepals, less than half the length of the flower; these are fused at their bases, and four lobed above. The four petals are unfused, flaring outward beyond the sepals. There are six stamens of equal length, projecting beyond the petals. A well-developed pale green nectary disk in the base of the flower produces abundant nectar. The elongate anthers are attached to the filaments at one end and project beyond the petals; anthers are straight when young, coiling tightly after the pollen is released. The pistil has a large, superior ovary on a long stalk that projects beyond the petals when young and further elongates as the fruit matures. The style is short and the stigma is minute. In some flowers, the pistil fails to develop, creating male flowers in the same clusters as bisexual flowers. The main bloom period is April and May,¹ but flowers may be found in all months.

The fruit is a conspicuous, leathery, inflated, egg-shaped bladder that hangs from the branch ends. Fruits have been likened to fat pea pods,^4,23 and lanterns;²⁴ boxing bags (“speed bags”) also come to mind.²⁷¹ The bladder is green, sometimes purplish when young, aging to paper-bag brown and usually contains up to 12 spherical brown seeds. The fruit  may persist on the plant unopened for some time.

Classification ^2,7,59,143

Note: Since this writing, the scientific name of bladderpod has been changed to Cleomella arborea.

Bladderpod is a dicot angiosperm currently placed in the spiderflower or bee family (Cleomaceae). In the past it has been placed in the caper family (Caperaceae)^11,23 and in the mustard family (Brassicaceae).¹ The spiderflowers are closely related to the members of the mustard family, both having four petals and six stamens. In the mustards, two stamens are shorter than the other four; in the spiderflowers they are all of equal length. There are also differences in fruit morphology.

Members of the spiderflower family typically have leaves with three palmate leaflets, also four sepals, four petals and six stamens of equal length. The ovary is attached to the receptacle by a long stalk. The spiderflower family is a small family with about six genera and 14 species in California. Bladderpod is the only shrub; all other California species are are annual or short-lived perennial herbs.

There are three varieties of bladderpod in California characterized by the shape of the seed pods. The plants in the Reserve are var. arborea.

Ecology

Bladderpod, like most species in the sage scrub, has adaptations that buffer it from the climate and promote rapid growth and reproduction during the cool, wetter part of the year. Like toyon (Heteromeles arbutifolia) and coyote brush (Baccharis pillularis),  bladderpod’s pale, waxy coating helps limit water loss and keep the plant cool by reflecting the hot sun. Like the leaves of laurel sumac, bladderpod leaflets fold up along the midvein during drought to minimize direct irradiance and evaporation.²⁴

Human Uses

The flowers of bladderpod were (and are) valued by the Kumeyaay as a vegetable.^16,272 Flowers are hand-picked carefully to avoid the leaves. They are then boiled, often with several changes of water, to remove the bitterness. The remaining mass is hand-squeezed to remove the water. It is eaten plain or stewed with other vegetables such as onions, tomatoes and peppers. It is usually eaten with tortillas or mush.

Bladderpod is recommended as a plant for native gardens,^24,169,168 with the caveat that, because of the strong odor of the foliage, it be placed away from paths. Because of it’s bright color and copious nectar, it will attract a variety of bees, butterflies and hummingbirds.^109,134,168

Interesting Facts

Rarely will you find a bladderpod that is not accompanied by a small population of yellow-orange and black, shield-shaped harlequin bugs (Murgantia histrionica).^59,275 All stages of the bug have piercing mouthparts that they use to feed on the sap of the bladderpod. This sap contains mustard oils (glucosinolates), organic compounds similar to those in the related mustard plants. Mustard oils are toxic to most insects. Harlequin bugs have developed a tolerance to these compounds allowing them to feed on bladderpod.

Harlequin bugs are serious pests on mustard crops; if left unchecked, they can quickly destroy a field of cabbage or broccoli.⁴¹However, bladderpods persist for years, even while supporting a population of harlequin bugs. The factors that limits the damage of harlequin bugs to bladderpods have been the subject of study by scientists at the University of California.²⁷⁴ Harlequin bugs have two parasitoids (distinct from parasites because they ultimately kill their harlequin bug hosts). One parasitoid preys on both the harlequin bug and on the second parasitoid. The second parasitoid appears to have a greater tolerance for changing conditions. The feedback interactions of the bladderpod, the harlequin bug and the two parasitoids seem to allow a long-term, balanced coexistence of all four.