Book Review of "Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden"

Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden by Pennsylvania horticulturalist, Jessica Walliser, offers dozens of workable combinations using mixed-planting techniques. Traditional vegetable gardeners, who have grown their crops in rows, season after season, will be inspired to step out of their comfort zone; adding more flowers to attract pollinators, incorporating living mulches instead of using shredded bark, or planting carpets of thyme around cole crops to discourage cabbageworms. These are all modest endeavors with positive long-term consequences. Less traditional vegetable gardeners will be game to grab their notebooks and test out a few of the suggested combos. But this book’s audience extends beyond folks who focus on growing mostly vegetables. Gardeners who are invested in making their landscapes more habitat-friendly will also be motivated to experiment with the extraordinary mix proposed in these pages.

Long before the arrival of Europeans, Eastern Woodland peoples and Mesoamericans grew maize, beans and squash together in the same mound. In this ancient method of companion planting, the maize provided a sturdy stalk around which bean vines were able to grow, while beans, as members of the legume family, replenished the soil’s fertility by fixing nitrogen through their roots. The squash supplied living mulch thus maintaining moisture and shading out weeds. In folklore, this mode of planting became known as the “Three Sisters." More companions, or sisters, like pumpkins, chilies, and sunflowers, were often thrown into the mix.

Today in farming, the utilization of two or more species is often called interplanting or intercropping. For decades, organic farmers have lured pest insects away from preferred crops using decoys, or trap crops, thus averting the use of toxic pesticides. For example, Blue Hubbard squash (Cucurbita maxima origin) is grown in the corners of fields to draw squash bugs away from the zucchini.

While companion planting and interplanting are not new, what is new is a burgeoning wave of research about the interconnectedness between plants and the ecosystems that result. Polyculture is how scientists describe a planned agricultural system that mimics nature and those complex ecological relationships. Plant Partners elucidates an impressive amount of recent scientific research that provides sound evidence to support a wide array of mixed-planting schemes.  Through the conscious combining and layering of plants, other life will follow, including fungi, microorganisms, and a slew of bugs, and creatures otherwise known as arthropods. The greater the variety of plants, the more likely an ecological balance will be achieved, reducing the likelihood of cataclysmic pests and disease. Biodiversity and stability are the goals.

The author creates an expansive framework for re-thinking the evolving role of the vegetable garden. Not only should the vegetable gardener be concerned with growing better, healthier fruits and vegetables, but also in improving the environment in order to preserve and sustain the fecundity of our gardens and our planet for generations to come. In the not-so-distant future, will that enormous squash on display at the county fair be valued for its size alone? More likely the gardener will be esteemed and rewarded for the complexity of the eco-system in which that squash was grown.

Despite being cultivated spaces, gardens have the potential to mirror natural ecosystems. “When built and maintained with an appreciation for all of the life it can support, a garden becomes so much more than a place to grow food and pretty flowers. It becomes an important environment, capable of filling some of the void left behind by the development and destruction of so many of our wild spaces," writes the author.

Accustomed to regularly stooping down to pull up an errant dandelion, gardeners know that plants compete for space, light, water, and nutrients. They can crowd each other out. Many more subtle relationships between plants also exist and scientists are just beginning to explore those relationships. How do the lives of plants, and all the creatures and organisms that live around them, influence and affect one another? Walliser’s book looks attentively into these new insights: the allelopathic qualities of rye that can assist peppers, tomatoes, and eggplants to curtail the growth of weeds; the threadlike hyphae of mycorrhizal fungi and how increased biodiversity appears to help these fungi networks flourish; or how the native flower lacy phacelia (Phacelia tanacetifolia and P. integrifolia) serves as both green manure and as a nectar source for pollinators and many predatory insects that will keep pests in check.  

Walliser is a horticulturalist with a penchant for entomology. Two of her prior books have focused on insects Good Bug Bad Bug: Who's Who, What They Do, and How to Manage Them Organically (All you need to know about the insects in your garden) in 2011, and Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control, which won the American Horticultural Society Book Award in 2014. While she deftly enumerates and explicates many strategies to reduce weed and disease pressure, increase soil fertility, and utilize cover crops, much of her material focuses on pest management, biological control, and how to attract pollinators. What would the world be without bugs? Gardens depend on bugs. In fact, so does life as we know it, yet many studies and reports document that their populations are precipitously declining. Perhaps bugs will soon depend upon gardens.

Beneficial insects are important decomposers, pollinators, and pest predators. Parasitoid wasps are notorious for attacking hornworms. Often represented in books related to insects in what might be considered gruesome fashion, their tiny white larvae wriggling free from inside their doomed host, they are the poster child of the good bug. Before the larva can feed, the adult needs to be nourished as well. Walliser recommends “banker" plants. For wasps, this might include the nectar of several varieties of flowering herbs, like dill or cilantro. She offers actionable strategies to attract these and many other necessary pollinators and insects.

The book is fascinating reading for those gardeners who want to zoom in for a closer look at what’s really going on in their vegetable patch. How do those squash bugs even know where to find the zucchini, melons, and cucumbers? Using clear, straightforward language, she explains how insects navigate their way to crops gardeners are attempting to cultivate so that when suggestions are made about how to mitigate the piercing and sucking damage those hungry creatures cause, the reader understands the how and why of a particular strategy. Paired with nasturtiums (Tropaeolum majus), a study from Iowa State University found hopeful evidence that the scent of the flower masks the chemical cues squash bugs need to locate zucchini, a potential boon in that squash bugs are known to feed on their host plants throughout their entire life cycle. While the study was limited to summer squash, Walliser surmises this strategy might lessen damage to winter squash varieties as well. The added bonuses of growing nasturtiums for this particular control method are many. They are easy to seed, their orange petals are edible, they lure pollinators and they also have aesthetic value. To some, nasturtiums might even fall into the category of beautiful.

Striving for layers of growth, combinations of color, intricate foliage, and overall lushness within the vegetable garden is an exciting prospect. Walliser's descriptions of living trellises whet the imagination. Combining sunflowers (Helianthus annuus) and mini pumpkin vines (Cucurbita pepo) is only one possibility, reminiscent of the “Three Sisters" and the companion plantings of native peoples. The science in this chapter is put aside and Walliser's own aesthetic opinions and experience hold court, although, given time, the science might follow. Several of these pairings are appropriate for containers too. The design implications and edible landscape possibilities are endless.