|Coyote brush (Baccharis pilularis) photo by Art Shapiro|
I’ve always been suspicious of some of the popular companion planting advice of the sort dispensed in old books like Carrots Love Tomatoes. From what I understand research just hasn’t proven a lot of the relationships these sorts of books tout. What makes intuitive sense to me, however, is that biodiversity in in a garden can create habitat for beneficial insects and birds that can help keep our edibles free of pests. For thousands of years in Northern Europe that biodiversity was maintained through the use of hedgerows.
Now, thanks to a study conducted by UC Santa Cruz researchers Tara Pisani Gareau and Carol Shennan, we’ve got some solid advice on what sorts of plants can create habitat for beneficials. The study, “Can Hedgerows Attract Beneficial Insects and Improve Pest Control? A Study of Hedgerows on Central Coast Farms” looks at a set of specific plants used in hedgerows in California: common yarrow (Achillea millefolium), coyote brush (Baccharis pilularis), California lilac (Ceanothus griseus and C. ‘Ray Hartman’), perennial buckwheat (Eriogonum giganteum), toyon (Heteromeles arbutifolia), and coffeeberry (Rhamnus californica).
In their conclusion Gareau and Shennan note,
Planting a diversity of plants that have different floral architectures should increase the likelihood of conserving a diverse community of insect natural enemies. Coyote brush and yarrow would be especially important foundational plants in hedgerows. In addition . . . combining hedgerows with in-field floral plantings (in strips or randomly throughout) may increase the dispersal of small-bodied insect natural enemies through the fields.
Scott Kleinrock, who is in charge of the new Ranch project at the Huntington, tipped me off to this research and is making use of a lot of California natives to create the urban residential equivalent of a hedgerow. In short, a hedgerow in our yards and urban spaces means making sure to include lots of natives and flowering plants that can provide habitat for the types of critters we want. Hopefully this important research will be duplicated in other regions and climates with different sets of plants.
Now, I’ve got to get me some Baccharis pilularis!
ETA: Apologies for being California-centric here, but we don’t know of any research studies on native plant hedgerows in other places. However, be sure to check out this Mother Earth News article about living fences, which we’ve posted about before.
ETA 2: From our comments: check out the region-specific guidelines for plants which support pollinating insects, put together by the good folks at the Xerces Society.