Miss Floribunda: Bad company ruins good gardens
Dear Miss Floribunda,
Last month you wrote that tomatoes should be grown separately from corn. This was news to me. I do know about companion planting and that corn likes beans and squash and that Native Americans planted them together and called them the Three Sisters. However, I didn’t know plants could be enemies of each other! So, just why don’t corn and tomatoes get along? Is there some family feud? What’s the dirt on that?
Digging Up Data on Decatur Street
Dear Digging Up Data,
Are you trying to tempt me to dream up a turf war between the Solanaceae and the Gramineae families, featuring savage competition for nutrients, scandalous cross-pollinations and hits from hired insects? I could call it “Goodveggies.” If that’s too corny, I might tell of a rivalry among lethal legumes (pea shooters picking off has-beans?) called “The Podfather.”
However, if we’re going to anthropomorphize plants, we’d do better to consult a once-popular 19th century novel: Elective Affinities, by Johann Wolfgang von Goethe. Goethe posits that combining certain personalities will lead to such predictable results as amorous infatuation or violent crime. He makes a comparison to mixing chemicals in a laboratory. This brings us back to plants and how they affect each other, beginning with the soil they share. Some plants exude chemicals that are harmful to some other plants, or helpful in repelling insects and disease-carrying organisms. Others vie for the same nutrients, a serious problem if root depth is the same. Others attract insects that are either harmful to another plant or, on the contrary, beneficial.
The reason that corn and tomatoes should not be planted together is that both are susceptible to a number of the same fungi. They are both attacked by moth larvae: Heliothis zea, known both as corn earworm and as tomato fruitworm; Manduca quinquemaculata, known as the tomato hornworm; Agrotis ipsilon, or black cutworm.
Now, if you are considering planting corn with beans and squash, you might be interested to know that the beans that Native Americans planted with corn were not green snap beans but the drought-tolerant tepary beans (Phaseolus acutifolius), which dried well and could be stored. For the same reasons, it was winter, rather than summer, squash that was the third “Sister.”
If you plant green beans, it makes sense to choose a vining pole bean that will climb the corn. Any beans you plant will add nitrogen to the soil, which will feed the corn and squash. The sprawling squash vines will smother weeds, as well as cool the soil and help it retain moisture. The tall corn will shade the squash and beans from the fiercest solar rays.
Although squash blossoms are gorgeous, as are the blooms of scarlet runner beans, you’d do well to add a useful and quite beautiful edging to your bed with nasturtiums. They come in spectacular colors, they enrich the soil, and their odor repels many noxious insects, while attracting some beneficial ones. You might consider planting an early spring garden of peas and radishes in the bed that you will add tomatoes to when the soil warms. Peas will add nitrogen to the soil. Radishes, which burrow down into the soil, will improve texture and tilth.
Let’s not neglect the tomatoes, which can be planted in another bed at a safe distance. Now, if you want a soap opera, here’s food for one: Tomatoes get along just fine with beans and squash despite the latter’s alliance with corn. If revenge is desired, those cucumbers and carrots so often paired with tomatoes in gardens will be perfectly happy fraternizing with corn, and vice versa. Carrots, by the way, can be planted earlier than tomatoes and will help soil tilth even more effectively than radishes because they delve deeper. (I might add that radishes will not scruple to grow with tomatoes just as compliantly as with corn.) Other congenial spring plantings are lettuce and spinach: As the tomatoes grow, their shade slows the bolting of these cool-weather plants.
Most essential for the tomato garden, however, are garlic and onions. They repel the red spider mites, along with most other insects, bad or good, that like to attack tomatoes. Their allium relative, chives, has sweet-scented mauve flowers to attract beneficial insects — for a while.
You might want to plant nasturtiums and marigolds to bring bees, butterflies, ladybirds and other beneficial insects. Another benefit of including marigolds near tomatoes is that their roots exude a chemical that kills root-knot nematodes — nasty microscopic worms that consider tomatoes their favorite host to impose on and eventually kill.
Lovely herbs to make tomatoes and beneficial insects happy are lemon balm, thyme and basil. Parsley is also very beneficial, but should be kept away from lettuce. Do not plant dill near tomatoes. Peppers, by the way, should not be planted with tomatoes every single year because they are also in the Solanaceae family and can share diseases. The nemesis of the Solanaceae family, however, is the Brassica family. Don’t even think of planting kale, cabbage, turnips or broccoli with tomatoes unless you would like to see your green thumb defeated by the Black Hand.
Of course, there are other alliances and misalliances among plants that could be explored. I fervently hope that the Hyattsville Horticultural Society (HHS) will soon be able to have public meetings so we can all exchange information. Please keep checking the HHS website, hyattsvillehorticulture.org, for information.