Companion Planting or Inter-planting
What is it?
The intermingling of plants, similar to what occurs in nature, but done deliberately for a variety of purposes. In a food garden, herbs, vegetables and flowers can all be successfully grown together.
Why is it done?
• Plants themselves grow together or avoid each in nature e.g., vines may use tall plants as support
• Plants may thrive in the shade of a sun-grabbing or wind-protecting plant
• There are beneficial root interactions as well, for example, legumes (e.g., beans, peas, clover) are nitrogen-fixing plants and reinvigorate soils that are depleted by plants that draw nutrients from the soil heavily (e.g., tomato, squash)
• Certain plants, such as marigolds, repel insects with their musky smell and others may mask the presence of a vegetable from a predator pest with their sweet smell. Of course, sweet smells also attract bees and butterflies for pollination as well. Still other plants, such as nasturtium can act as a trap or sacrificial plant for pests such as aphids
• Inter-planting allows more plants to be placed in an area than might otherwise occur in conventional gardening, because they will not necessarily be competing for the same resources from the soil
• Other cited reasons for inter-planting more folk wisdom than scientifically proven, such as radishes not getting along with peppers. But one proven interaction is that compounds within alliums (e.g., onions) are secreted into the soil and they discourage beneficial bacterial growth on legume (e.g., beans) roots.
How to do it?
First and foremost, mix it up. There is no rule that you have to plant things in rows, although that can be convenient. An easy way to inter-plant is to plant in squares or rectangles in which you decide on a grouping of plants that you have placed together for a specific purpose. Examples:
To create shade for plants that need it:
• You can plant lettuce and greens that don’t require full sun in the shade of taller plants such as tomatoes.
To repel insects:
• Marigolds may be planted throughout your garden or along the edges to confuse pests and mask the scent of vegetables
• Garlic/onion planted in locations where they don’t conflict with other veggies (see Plant Interactions below) but deter various pests
• Nasturtiums and borage repel squash borers
To attract or trap pests:
• Basil and nasturtiums attract aphids to the bottom side of their leaves. Aphids may attack almost anything in the garden with soft/green stems.
To encourage/discourage plant Interactions (this is more folk wisdom than proven):
• onions and garlic can be planted with brassicas, such as cabbage or broccoli … but need to be kept away from peas and beans
•brassicas (cabbage, broccoli, kale) should be kept away from the nightshade family (tomatoes, peppers)
• Tomatoes, rosemary and basil taste good together and are said to have improved flavor when grown together
• Keep fennel away from pretty much everything
To discourage weeds:
• Inter-planting allows for planting crops in closer proximity to each other than regular spacing. This means less bare soil and consequently, fewer opportunistic weeds
Some additional specifics:
• Lettuces and many greens can be intercropped with just about anything, including onion. Mix greens with herbs and flowers too.
• An historic example is the “three sisters”: corn, beans and squash. Start with corn seed planted in a mound of soil. Follow when the corn is out of the ground with alternating pole bean and squash seed. The corn provides a structure for the bean to climb. The beans provide nitrogen to the soil. Squash discourages the growth of weeds and helps with water retention.
• Avoid placing garlic near anything where it might affect the flavor of its neighbors, like strawberries or brassicas
• Marigold is a good companion to just about anything. They discourage parasitic nematodes in the soil in addition to their smell-masking properties
• Plant lettuce, mustard, spinach, and chard in the shade of taller plants like tomatoes, and peas, cucumbers and other trellis-climbing plants
Avoid planting the similar plants in the same spot as they were planted last year because they will deplete the same nutrients from the immediate area where they were planted. Make a plan yearly based on moving your plants around. This is another advantage of planting in squares: if you know roughly what you had together in previous years, you just rotate the squares around the garden.