Last week, I got an e-mail from none other than Annie of Annies Annuals! This made me squeal with excitement because I am a TOTAL nut case when it comes to horticultural celebrities (ask me about the time my friend Virginia and I ran into Dan Heims of Terra Nova at a trade show...), and I think Annie totally qualifies as one. She went on to say nice things about my blog (!!!!) and then asked me if I was up for providing "Sciency answers" to random questions about plants. To which I reply, "TOTALLY!"
And so, I introduce to you the newest Greensparrow Gardens feature: Sciency Answers! If you have a question requiring a sciency answer, just e-mail it to me -- engeizuki at gmail dot com -- and I'll get right on it.
Annie's question was why some plants exude gummy substances on their buds -- for example, Grindelia arenicola. She even sent a picture:
But kind of cool. Now I want one.
So why do they? So they won't get eaten. Slimey grossness to avoid being eaten is a common theme for plants. The seeds of many species of salvia exude slime which has been shown to discourage things (mostly rodents) from eating them. If you have ever deadhead a petunia and come away with a grossified hand, you know they are covered with little sticky yucky hairs -- some scientists bred the sticky hairs away, and hey presto: Without the sticky yuck, the plants got gobbled up by whiteflies.
In the specific case of Grindelia, it appears that they are so serious about not getting munched upon that they they produce chemicals which show "feeding deterrency towards aphids" (see the paper here) so it appears they cover their flowers with yucky tasting glop so that when aphids and other insects stop by for a bite to eat, they end up grossed out and heading off to find something else for dinner.