Flora Fact: Going Green
When rain stops, paloverde trees drop their leaves and photosynthesize through their bark.
By Eva Frederick
After a childhood of meticulously colored tree drawings — brown bark, green leaves, blue sky — the first paloverde tree I saw turned my idea of trees upside-down. Here was a mid-sized tree with standard green leaves and lush yellow flowers with red flecks, but something was off about the color of the bark: bright yellow-green.
After a few years and additional research, the iconic Southwestern tree’s green bark made a lot more sense to me. Paloverde is Spanish for “green stick,” and the tree’s surprising bark is not just for decoration — it’s part of what makes the paloverde so suited to harsh Texas heat.
Paloverde trees are drought-deciduous. They drop their leaves in times of water stress but continue to turn sunlight and water into sugar with their bark. The green color tells us that there’s lots of chlorophyll in the bark for photosynthesis.
One product of photosynthesis is oxygen, which plants release in exchange for carbon dioxide. This exchange is done through tiny pores on the plant’s leaves, called stomata. Stomata also release water in a process called transpiration.
Transpiration serves several purposes. It keeps a steady flow of water moving through the plant — as if the water’s being sucked through a straw. The evaporating water cools the plant and keeps leaves from overheating.
However, in times of severe drought, losing water vapor through holes in leaves is less than ideal. To prevent this, paloverde trees drop their tiny leaves and survive with the help of those unusual green trunks.
Texas has two main types of paloverde: Texas (border) paloverde and Jerusalem thorn (or retama). These delicate plants can be seen in much of South and Central Texas.
When paloverde trees bloom, they look like bright yellow puffs of smoke, and those flowers are edible — usually eaten raw in salads or candied for desserts. Paloverde trees are members of the legume family and produce edible beans, which can be eaten raw or cooked in savory dishes.
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