Tomato Tar

Posted: February 17, 2011

I’ve been working with tomatoes for many years. Like everyone that works with tomatoes and many other plants, after we’re done, there is goo of various kinds all over our skin and clothes. With tomatoes, that goo starts off green and if not removed relatively quickly, will turn black. In an article in the monthly newsletter “Growing for Market” Lynn Bycznyski, responded to this very issue by asking: What is the greenish-yellow powder you get all over your hands and arms when you pick tomatoes? She asked Dr Chris Wien, Cornell Horticulture Professor, for more information. I found his responses and related information very interesting.

The green substance from tomatoes is made up of a number of chemicals that are released from hairs that cover tomato leaves, stems and to a lesser extent, fruit. Under a microscope, these hairs look like miniature water towers. These towers are glands that are loaded with a variety of chemical compounds. As we handle the plants the glands burst and leave that goo on our skin. Technically, the hairs are known as secretory and glandular trichomes (hereafter known as SGT’s). About 1/3 of all vascular plants species have SGT’s. These are specialized cells that occur in the epidermis of the plant.


What good are SGT’s? Contained within SGT’s are secondary metabolites. These compounds aren’t used for growth or reproduction of the plant, thus are secondary, but do have other important functions. In tomatoes, SGT’s contain acyl sugars, terpenoids and flavonoids. These compounds are believed to protect plants against environmental assaults from insects, diseases, extremes of heat and light, ozone and other challenges to plant health and survival. Think about how it must be for a small insect to move around and feed on a plant that is loaded with sticky exploding balls of goo. There’s more to that green slime on your hands and arms than just irritating you.