Companion planting can be defined as the close planting of different species based on their ability to enhance one another's growth or offer some form of pest protection or other advantages. Sometimes this is a matter of choosing plants with different growth habits that don't compete with one another or those that have different nutrient needs that make efficient use of soil. Strategic companion planting is especially important in small gardens or wherever careful space planning is needed.
Sometimes companion planting is not just a two-way partnership; the best plant synergy may require a three-way partnership.
An Ideal Three-Way Companion Partnership
There are many good companion plants for tomatoes, but how do you work them into an overall garden plan without just feeling like you're wasting valuable veggie-growing space? Here is an idea for getting the most use out of a popular tomato companion plant—borage: an old-time herb that brings unique merit as a companion plant.
Borage (Borago officinalisis) is a perfect companion plant for tomatoes because, when planted nearby, it deters tomato hornworms, a real pest for many tomato growers. Its bright blue flowers, shaped like tomato blossoms, are an attractive ornamental addition to the garden as well.
You could just stop there, but why not add another crop and really get the most use out of the great properties of borage? Not only does the scent of borage discourage tomato hornworms and some other damaging insects, but beneficial insects such as bumblebees, honey bees, and other pollinators adore borage blossoms. And, happily, borage blooms fairly steadily up until frost. So it makes sense to make good use of all of those pollinators being attracted to your garden bed by the borage. One great option is to plant either summer or winter squash nearby. Borage can also serve the same function for other fruit-producing plants, such as strawberries.
The three-way partnership works like this: As tomatoes flower and begin to produce fruit, borage planted near and between the tomato plants deters hornworms and simultaneously attracts bees and other pollinators to fertilize the late-season squash you've planted, which is just now flowering and getting ready to produce fruit.
A Planting Plan
One good layout plan is a 4-foot by 8-foot bed in which a tomato plant is planted in each corner of the bed, with a borage plant growing between each tomato plant. Then, in the center of the bed, plant two late-summer squash plants. The squash will receive plenty of sun in the center of the bed and will be able to trail beneath the overhanging foliage of the tomato plants, while the borage benefits both. And everyone will be happy and healthy!