Vida Poole of Chilmark found herself with quite a sticky situation.
While trimming a trail, she noticed what she called a “gelatinous display” on a wild cherry tree. A blob of amber gum was sitting atop a bulging branch. Her identification app of choice told her it was a jelly fungus, Tremella mesenterica, commonly called witches butter or yellow brain, and asked if I thought the same.
That identification didn’t gel with me since the photos lacked the brain-like folds. Like a good gumshoe, I took up the challenge to solve the gooey mystery. Vida also thought maybe cherry canker was the culprit, which is a bacterial-caused wound in a tree. Now she was getting closer.
The gummy substance that she observed was the sap of the cherry tree that had oozed out as a result of some sort of tree trauma. Called gummosis, the exuding of sap is the tree’s response to stress, injury or disease.
Gummosis occurs often on fruit trees, both wild and cultivated. It can be caused by a myriad of factors, including environmental conditions, tree health and predators, especially insects. Anything that weakens the tree can cause gummosis.
Too much water, too little water, damp conditions, sunscald and mechanical injury such as natural breakage or poor pruning are causative. Bacterial, fungus and viral factors are also to blame. And insects can also be contributory.
When insects are to blame, they leave behind clues. Look closely for insect holes in the bark, frass (insect droppings) in the gum, or peel away the bark to see if you can find the dastardly doers in person. The plant’s extrusion of sap is its way to try to push out the insect, and if it succeeds, you might see the insect in the gum, permanently encased and no longer a danger to the tree.
The sap or gum on the outside can have a variety of appearances. It can be liquidy and run down the tree or branch. It can be gelatinous and sticky and can even set up like hard candy. Which of course got me to thinking about eating it. Would it taste like sweet syrup, chewing gum, jolly rancher or butter brickle?
I was ready to rush to Vida’s place to try it out. But leave it to the internet to gum up my plans. One source called the question of cherry sap and gum edibility “fascinating and cautionary,” suggesting that the substance, while sweet, was potentially toxic or could cause an allergic response. Toxicity, it continued, was due to the fact that parts of black cherry contain cyanogenic glycosides, which can release cyanide when metabolized.
Other sources disagreed, and videos of folks taking fingerfuls of the gum and eating it abounded on YouTube. Mentions of Indigenous uses, medicinal opportunities, and employment as flavorings rounded out the research. Like George Washington, I cannot tell a lie: I did not chomp the cherry tree. Prudent foragers, like myself, will just stick with the cherries and leave the gums for the more adventurous (and non-risk-averse) wild eaters.
Gardeners, on the other hand, who wish the goo to be gone do have some options. Attempt to identify the cause and consider taking action if you are concerned. Improve environmental conditions, prune out cankers, protect wounds, apply the ‘cides, and provide extra care to mitigate or manage the ailing tree.
One or all of those solution would work if you have the gumption to stick to it.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.