Damrosch reports that her farm recently experimented with grafting her favorite eggplant varieties onto an extravigorous rootstock, a technique that combines two different plants: The top of the plant is a variety selected for its high-quality fruit, and the rootstock, or bottom, of the plant is a variety known for its disease resistance and vigor. The result yields a superhealthy,
fast-growing eggplant. "Grafting works great," says Damrosch, "but it's a tricky procedure that only a very adventurous home gardener would want to try." Fortunately, grafted eggplants are now available from some specialty nurseries, including Territorial Seed Company, which plans to ship grafted eggplant seedlings in spring 2012.
Eggplants grow into bushy plants 2 to 3 1⁄2 feet tall. The larger a plant grows, the more fruit it supports. The key to achieving a generous late-summer harvest is to encourage strong, healthy growth as soon as the plants are in the ground. Begin prior to planting by working 2 to 3 inches of compost into the soil, adding a balanced granulated organic fertilizer at the same time (follow the manufacturer's recommended application rates). Plant out seedlings when the soil is 65°F or warmer and all danger of frost has passed.
In climates with long, chilly springs or short summers, black plastic mulch helps eggplants thrive, though it's not the most aesthetically pleasing option. Ground covered by black plastic will be 8°F to 10°F warmer than uncovered soil. Plastic films also help to inhibit weed growth. Recommended brands are Solar Mulch, which is a dark plastic material, and biodegradable black cornstarch-based films such as BioTelo. To use these mulches, stretch the material smoothly across the bed and then pin it into place with landscape-fabric staples. Punch planting holes with a bulb planter or cut Xs through the material at each planting spot.
Transplants should be set no deeper than they were in their pots, and spaced at least 18 to 24 inches apart in rows 2 feet apart. When the first set of flowers emerge, pinch them off, recommends Rosalind Creasy, author of Edible Landscaping (Sierra Club, 2010). In addition to making the plant develop several fruiting branches, this will, she says, "encourage the plant to put more energy into creating leaves and roots instead of one big fruit." Creasy fertilizes her plants with homemade compost and a little chicken manure when planting, and applies fish emulsion about 6 weeks later. To keep plants upright and fruit clean and intact, she recommends staking with bamboo poles.