Nothing evokes the feeling of summer quite as much as the smell of tomatoes from the garden. Earthy, fresh, bright. The smell can linger in our kitchens after we slice the heirlooms and beefsteaks, translating the smell to taste—the taste of summer.
While we might have a pure and positive relationship with these backyard gems, Marjorie Weber says that if we zoom in, we’ll witness a much more complicated drama.
“What we’re smelling are these tiny hairs on the tomato leaves. They have little globs on the ends that are like toxic lollipops to herbivores,” says Weber, LSA assistant professor of ecology and evolutionary biology. “When an herbivore brushes over the leaves or tries to chew them, the lollipops are like little explosives that release chemicals that are really unpleasant for the herbivore. But to us, it’s just a nice, lovely smell.”
Weber explains that gardens are rife with these kinds of dynamics. “There’s just a lot of drama,” she says. “Some are friendly interactions, even love affairs between insects and plants, like with pollination. But others, like the tomatoes’ leaves for herbivores, are intense battles. Plants face pressure from herbivores or insects like caterpillars and have developed different strategies to defend themselves against those threats.”
Micro-Dramas and Macro-Impacts
While it’s easy to see a rabbit or deer chomping on our lettuce plants or hydrangeas, other, microscopic dramas are happening every day. A rich microbial community lives in the soil of every yard and on the leaves of every plant. These organisms interact with insects, some of which, like mites, are so small that they’re difficult to see with the naked eye. Despite their size, they play a huge role in the overall health of the garden. “If you look at a green leaf, and it looks clean and like there’s nothing going on, there’s often a really rich ecosystem and an entire hidden world playing out on the leaf,” says Weber.
Another insect with a surprising lead role? Ants. Weber says ants can either protect plants or assist in the plants’ destruction. Which side they’re on can change at any moment. “Ants can be good guys or bad guys. They’re easily persuaded,” Weber says. “Some plants release nectar from their leaves to attract ants, so that they can guard the plant from things like caterpillars. But if aphids find the plant and start chewing on the leaves, the sweet honey dew they produce can convince the ants to turn and start siding with the insects that are going after the plant.”
Despite these chaotic dynamics, this kind of drama is actually good for the garden and helps sustain biodiversity. A variety of plant species that foster a multitude of habits is vital for our ecosystems, Weber says. “Biodiversity scales up. The more plant resources there are, the more diverse insects, the more diversity in the food chain, which is beneficial to humans and animals.”
Weber says the goal isn't pristine gardens with perfect tomatoes. “Take pleasure in what your garden is providing to the overall habitat. Perfect tomatoes are lovely. But when a tomato gets ruined by an herbivore or insect? Try to remember the fascinating biology that’s happening all the time,” she says. “Enjoy the drama.”