- Ph.D. 1970, University of Missouri-Columbia
- Agroforestry; physiology of mycorrhizae.
- Garrett’s research interests are equally divided between developing temperate zone agroforestry systems and conducting mycorrhizal research. Agroforestry is the practice of growing trees and crops or trees and livestock on the same acreage. Mycorrhizae are symbiotic associations in which a plant’s secondary root system is invaded by specific fungi during periods of active growth. Increased water uptake along with increased selective absorption and accumulation of nutrients ultimately results in increased plant growth. Current agroforestry research is focused on developing systems that are environmentally and financially sound. While numerous tree species are under experimentation, emphasis is placed on eastern black walnut due to its value for wood and nuts. Mycorrhizal research emphasizes studies of the biochemical and physiological roles of boron and magnesium in the colonization process.