By Bobbie Stephenson.
The evergreen bladderpod (Peritoma arborea; previously Cleome isomeris and Isomeris arborea), with its silvery-gray leaves, is native to southern California and Baja California. In native habitats, this mounding shrub grows from the coast through the inland valleys and foothills (up to 4,000 feet in elevation) to the high and low deserts. The bright yellow flower clusters, from which green 'bladder' seed pods hang, stay on the plant almost all year and attract hummingbirds, butterflies, and many kinds of bees. Quail, finches, sparrows, and doves flock to this plant. Some people consider the bladderpod to be pleasantly fragrant, but many consider the smell to be unquestionably disagreeable.
Whichever camp you're in with regards to your judgment of bladderpod's odor, there is one animal in particular that does not turn up its nose at this plant. When I was a graduate student at San Diego State University, a professor and his students were investigating the harlequin bug (Murgantia histrionica) and its relationship with bladderpod. The bug sucks sap from its host plant's flowers, leaves, and leathery, inflated seed pods. In addition to being a food source for the harlequin bug, chemical extracts from the plant are used as a defense against birds and other predators, who are warned by the bug's bright orange and black coloring. And if you have any doubt, as a member of the stink bug family, harlequin bugs definitely live up to their reputation!
A harlequin bug can spend its entire life on one bladderpod plant, or on a closely-related crop plant, such as cabbage, where its presence will not be appreciated as it can become a serious pest. If you are not growing cruciferous plants, however, and you're open to the possibility of observing the plant–animal relationship between harlequin bugs and bladderpod in your garden, setting the stage for this is as simple as getting some plants established.
Easy to grow from seed in the garden, bladderpod readily reseeds and will reach nearly full size (about five feet high and wide) in a year. These tough plants can grow in some difficult situations, such as south-facing slopes, salty coastal bluffs, and alkaline soils. As an added bonus, bladderpod is drought-tolerant and fire-retardant, and it can survive on natural rainfall, though it would prefer weekly summer watering in drought years.