Poisonwood

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Metopium toxiferum

(Metopium comes from an ancient name for Ferula.  Toxiferum means “bearing poison.”)

Anacardiaceae, the Cashew Family

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Funny how when a plant, or person, becomes known for a single prominent feature that single feature comes to define them with diminished attention to all else.    Poisonwood’s defining attribute is poison.  It causes dermatitis in some people.  A giveaway recognition feature is ominous black splotches on the foliage and bark.    

Poisonwood flowers. All plant pictures today by John Bradford.

Assuming speculatively that there actually is a relationship between that black staining and toxicity, it is interesting to see how the tree sequesters “black death” in its black inner trunk and in its black inner bark suppressing microbes and  insects.   

Is that black staining a nasty poison protecting the tree from becoming hollow? And look at the inner bark.

Same itchy family as Poison Ivy, and Mangoes and Cashews.  OK then, that is all we need to know.   But you might feel otherwise if you were a White-Crowned Pigeon.

WCP by Dan O’Malley

If you were a White-Crowned Pigeon there wouldn’t be very much of you in Florida, mostly just the Everglades, the Keys, and here and there around Miami-Dade.    The species ranges from the southern tip of Florida down through the Caribbean.   Guess what has an almost-matching geographic range: Poisonwood.

Turns out Poisonwood berries are the favorite food for the WC Pigeon, to the point that the availability of the berries influences the bird’s distribution, seasonality, nesting behavior, and reproductive success.   And the pigeon undoubtedly helps distribute the seeds. A problem for the pigeons is humans don’t like Poisonwood, which is suppressed in parks and yards.

Pigeon food

That fact ties in with a broader botanical oddity.   Which is:   Woody plants in Florida (and to unclear extent elsewhere)  found in stressful habitats and having pea-sized fruits dispersed by birds have an inordinate tendency to have separate male and female individuals (to be “dioecious”).    Dioecy tends to be unusual in the plant world overall,  yet dominant in Florida bird-dispersed woody plants in certain stressful habitats.   Examples:  Poisonwood, Wax Myrtle, Myrsine, Gallberry,  Dahoon Holly,  Smilax (not truly  woody),  Seagrape, Buttonwood, Wild Lime,  Winged Sumac, and Florida-Privet.   Although noticed variably by different botanists, this vague tendency is not thoroughly explained, the most common interpretation being that in some stressful environments it is advantageous for separate plants to specialize on male or female (fruit-making) functions.    Bird-dispersed species then often are clustered thanks to birds sitting in trees and raining seeds, the resulting clusters containing the male and female individuals needed for the next round of seed-making.   In any given cluster, one male can provide pollen for multiple females.