Parkinsonia

Fabaceae

•  Leaf shedding helps the palo verde conserve water. When moisture is plentiful, tiny leaves manufacture food. As soon as moisture becomes scarce, the leaves are shed to cut down on water loss, but photosynthesis continues in the chlorophyll-containing bark.
• The yellow-blossomed paloverde grows only in dry washes where there is water a few feet underground.

• The Parkinsonia genus which comprise the palo verde tres-whose name refers to their distinctive green bark- are another group of closely related trees that rely on photosynthetic stems yet also form leaves after spring wains. These species keep their leaves only for a matter of weeks before shedding them and relying on green stems for photosynthesis over the remainder of the year. Parkinsonia is an interesting genus in that it occurs widely in arid and semi-arid regions of both the Americas and Africa. While it might seem tat the largest photosynthetic area of these trees must be on their broad, green trunks, the majority of photosynthetic stem surface area is actually in the first- and second-year stems. Palo verde species are not able to fix atmospheric nitrogen, yet they successfully colonize nutrient-poor wash habitats. "California Desert Plants, Philip W Rundel, Robert J Gustafson, Michael E Kauffmann."