Plant Partners: Science-Based Companion Planting

Jessica Walliser, author of Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden

We’re joined by Pittsburgh-based horticulturist and author Jessica Walliser to talk about her new book Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden.

There is a lot of folklore that finds its way into discussions about companion planting. Walliser explains that her hope is to reboot the term “companion planting” by looking at it through a scientific lens.

What is Companion Planting?

Walliser says that companion planting is purposely planting two or more plants close together to get some sort of benefit.

Companion planting does not have to mean putting two plants together at the same time, however; it can also mean growing plants in succession.

Common terms used in science that overlap with the idea of companion planting are:

• Intercropping

• Plant partners

• Interplanting

• Polyculture

Benefits of Plant Partners

In her book, Walliser has chapters on seven different benefits of using plant partners in the vegetable garden.

• Soil preparation and conditioning

• Weed management

• Support and structure

• Pest management

• Disease management

• Biological Control

• Pollination

An example of pest management is using “trap crops” to lure pests away from other crops. Squash bugs prefer blue hubbard squash to other squash varieties—meaning it can be used as a “trap crop.”

A plant partnership that helps to control aphid problems on lettuce is to grow sweet alyssum as a partner. The alyssum flowers are a favourite of both predatory and parasitic insects that help to control aphids.

For weed management, there are cover crops that suppress growth of weed seeds the following season. Those same cover crops also build soil structure as they decompose.

Living trellises are functional and can be aesthetically pleasing. A good example is using corn with beans.

Ever Heard of “Biodrilling”

An example of a plant partnership to help prepare the soil is the use of deep-rooted forage radishes as “biodrills” on heavy clay soil.

These plants have long tap roots that penetrate heavy soil. The roots are left in the soil to decompose instead of harvesting them. Walliser explains that it’s like using a living drill instead of tilling the soil!