Monday, June 20, 2011

The Palo Verde: foraging and life history

Some Palo Verde bean pods ready to have their green beans removed and eaten.
While June in the Sonoran Desert may be oppressively hot and dry, there is an abundance of food available to the forager.  One of these foods comes from the Palo Verde (Parkinsonia microphylla).   Possibly the most common tree of the Sonoran Desert, it flowers in April and May, and produces seed by the end of June.  The seed is ready just weeks before summer monsoon rains which usually start mid-July or so.  Freshly shed seeds readily germinate in the hot rains of late July and August.  While a lot of desert plant seeds require a decent amount of rain to germinate, Palo Verdes don't require much rain at all, maybe a half inch or so.  Instead of depending on one single large rainfall event for germination, rather germinate as soon as it is wet and hot, then hope more rain falls in the coming days and weeks so they can become established.  If more rain doesn't come after germination, the seedling unfortunately dies.  Death due to lack of water is a cruel reality in the desert.  Hopefully seed produced next year will be able to grow into established trees with sufficient rainfall.  If you think about it though, each plant only has to produce one established offspring to maintain the population, and that means millions of seeds and seedlings that die every year and only a handful of seedlings that survive to maturity.  This is absolutely normal, keeps the population stable and prevents it from literally taking over the world!  So foraging has little if any effect of the success of this species.
Palo Verde trees growing along a dry wash.
Being the Palo Verde bean is almost as hard as a rock, it is indigestible.  Deer and javelina will still eat the beans but not digest them, instead they will simply pass though the animal unharmed.  Amazingly, passing though an animals digestive tract may actually aid seed germination and deposit it in an ideal location.  For us humans however, we need to eat the beans while they are still green or risk breaking our teeth.  The process of foraging Palo Verde beans is quite easy.  Mid-June or so, simply find some Palo Verde trees that have seed pods.  Pick pods off the tree that are green to tan colored but have green seeds inside.  Its pretty easy to collect a lot of pods from a few trees.  Once you have some pods remove the green beans from the pods.  This can take awhile.  These are the edible portion of the bean pod and taste somewhat like a mild green bean.  They can be eaten raw or cooked.  I have heard of other people eating the entire green pod early in the month of June.  I however have found the green pod to be way too stringy and chewy to eat.  I also suppose the rock hard seeds could be eaten if they were soaked and cooked, but I haven't tried this before.
The green Palo Verde beans removed from bean pods like in the picture at top.
For now anyway, I am sticking to eating the green beans once they are removed from the pod.

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