Calystegia stebbinsii

Calystegia stebbinsii is a perennial herb producing climbing, white haired, vine-like stems approaching a meter in maximum length. The leaves are up to about 5 centimeters long and palmate in shape with 7 to 9 long, narrow lobes; the distinctive shape of the leaves make the plant easy to identify among the morning glories native to the region.

The inflorescence bears flowers atop long peduncles, each flower about 3 centimeters wide and white or cream-yellow in color, sometimes tinted with pink. They are pollinated by bees and other insects.[5] Like many other chaparral plants, this species has seeds which are stimulated to germinate by exposure to wildfire.[4][1] It also reproduces via rhizome.[5]

The plant's type specimen was collected by G. Ledyard Stebbins in 1970 outside of Placerville, California.[3] The species was described to science and named for him in 1974.[6] The plant is known from only two locations, each containing a scattering of occurrences.[3] Both locations are on the Pine Hill intrusion, a section of gabbro-based rock that oozed as magma into the surrounding rock and then solidified there, eventually becoming exposed as the softer rock around them eroded away.[3] This gabbro intrusion yields red-colored soil that is rich in heavy metals, and some plants are adapted to this kind of substrate.[3] C. stebbinsii grows on the gabbro soil as well as the similar serpentine soil that can also be found in the intrusion.[3] Other species are completely limited to the gabbro sections.[3] The Pine Hill Ecological Reserve was established to protect these unique and often rare plant species.[5]

At the time it was placed on the endangered species list, at least one third of the known occurrences of the plant had been destroyed, mostly by development of its habitat.[3] Most of the sites that still existed were in danger of destruction.[1][3] With destruction and fragmentation of the habitat come associated activity such as road construction, trash dumping, off-road vehicle use, and herbicides.[1]

The plant does not tolerate shade, and when the brush around it grows too high and shades it out, it does not survive.[5] This suggests it requires disturbance, such as wildfire, to clear the overgrowth.[3] Fire suppression is detrimental.[1] Protected and managed areas of the habitat undergo controlled burns.[5]

• Jepson Manual Treatment - Calystegia stebbinsii
• Calystegia stebbinsii - Photo gallery