Coconut, Coppertone, saltwater, freshly cut grass and charcoal heating on the grill. These are some of the smells that reminded me of summer while I was growing up. And now as a gardener, tomato leaves make that happy list.
While there’s no shortage of Coppertone and saltwater on a California summer day (or any day in any season here, for that matter), the one smell that truly ushers in summer and closes it out is the heady, earthy, viney, fragrant aroma of fresh tomato leaves as you brush against them — either to stake up the vines in June or to pull up the last lingering plants in September.
Have you ever wondered where, exactly, that distinctive smell comes from? It’s not in the fruit, no matter how richly perfumed that heirloom variety may be. It’s only in the leaves, stems, and sepals (those little green “hats” on the flowers and fruits), and even on tiny seedlings that have barely seen the sun. It’s an unmistakable scent that no other plant shares, and people either love it or they hate it.
If you examine a tomato plant up close, you may notice that the foliage is covered in short, fine, hair-like structures. These hairs (what I affectionately dub tomato fuzz) are known as trichomes, and they serve a variety of functions and exist on many other plants as well. On a tomato plant, several types of trichomes are found on the stems, leaves, and sepals.
One type works to reduce evaporation of water by trapping moisture on the surface of the leaf. Another helps shield the plant against environmental stresses like extreme temperatures, and yet another type, glandular trichomes, contains crystals and oils in the bulbous section of the structures, seen here on the ends.
Images by University of California, Davis.
It’s believed that these crystals and oils are part of the plant’s defense mechanisms. They produce an unpleasant feel, taste and smell meant to protect the plant from insects that might feed on its foliage.
The essential oils are responsible for giving the tomato plant its characteristic smell, as well as the sticky yellow secretion you’ve probably had all over your hands after a day of harvesting tomatoes.
(As an aside, you might remember this post I wrote about a glycoalkaloid called tomatine that’s present in tomato leaves; it’s stored in the glandular trichomes as well.)
Within the oils, the volatile compounds that contribute most to tomato leaf scent are (Z)-3-hexenal, limonene, hexanal, (E)-2-hexenal, eugenol, 1,8-cineole, caryophyllene, beta-phellandrene, humulene, and linalool. It’s a little ironic that what might be considered “unpleasant” by pests can in fact be so intoxicating to the rest of us!
Like it or not, these compounds, collectively, are exclusive to tomato trichomes. If you want to add a distinctively tomatoey flavor to your tomato sauce or tomato soup, simply steep a few sprigs of tomato leaves in the pot the same way you would steep some bay leaves. As the trichomes burst and release their oils, the herbal aroma will infuse your dish with a deeper layer of flavor that can only be described as… summer.