Shortly after publishing an article about my quest to identify the world's actual lowest hanging fruit, David Karp, a pomologist at the University of California-Riverside who's known as the fruit detective, updated me with even more technical specificity. We had already settled on the fact that the lowest hanging fruit, in my framework at least, would be apples growing in dwarfed orchards, which are often set up on trellises similar to grape vineyards. I wanted to know whether there was a particular rootstock I could point to for its extremely small scale.
The shortest apple rootstock is called M.27, a "super dwarfing selection" whose moniker is slightly reminiscent of a British spy. As Karp's go-to authoritative source, CABI's Apples: Botany, Production and Uses, explains, it demands ideal growing conditions:
When grafted with most scion cultivars this rootstock produces trees that are 2.5 m or less in height and spread. Although of great value to fruit growers wishing to establish very high-density planting systems, it is unsuited to many soils and sites. Trees on M.27 have relatively shallow root systems and are not suited to poor, infertile, shallow or droughty soils. The rootstock induces heavy fruit set and, unless fruitlets are thinned severely, fruit sizes will be smaller than for trees on M.9.
Super dwarfing M.27. (Chart: Apples: Botany, Production and Uses)
So, if you ever happen to find yourself in the company of a pomologist, make sure to impress them with your knowledge of M.27.
Characteristic of Karp's curious and whimsical nature, he also left me with a colorful parting inquiry. "Now I have a question for you and your colleagues," he wrote. "What are the best songs about fruit that you know of?" His favorite is "Peaches, by the immortal Captain Beefheart." What's yours? —Ryan Jacobs