Horticulturist Walliser (Gardener's Guide to Compact Plants) takes a well-supported and helpful look at the practice of plant partnering, or placing certain plants in proximity with others to benefit both. She begins with the up-to-date science explaining why this long-standing gardening practice works: plants influence each other "through the chemical signals they produce, the underground network of fungi in and around their roots, and the toxic compounds some of them exude," and in other ways as well. Walliser proceeds to explore how common garden woes--regarding soil condition, weed control, pest and disease management, and so on--can be addressed with the right pairings. For example, medium red clover works well with winter squash because, as a vigorous grower that tolerates cold and also suppresses weeds, it "outgrows weeds in winter squash patches while still allowing the vines to ramble over it." Meanwhile, the legume hairy vetch can, after being cut down, provide a "thick mat" of residue that protects tomato plants from the fungal pathogens to which they're vulnerable. Walliser's lively guide will aid many a horticulturally minded reader. (Dec.)