The Seed Garden (Seed Savers Exchange, 2015) by Micaela Colley & Jared Zystro and edited by Lee Buttala & Shanyn Siegel brings together decades of research and hands-on experience to teach both novice gardeners and seasoned horticulturists how to save the seeds of their favorite vegetable varieties.
You can purchase this book from the MOTHER EARTH NEWS store: The Seed Garden.
Between its architectural branching habit and its glossy-skinned fruits, which vary in color, pattern, and shape, eggplant is as suitable for cultivation in a container or an ornamental border as it is for the vegetable garden. And given that this species has self-compatible, perfect flowers and pollination is easy to manage, gardeners can save seeds from multiple varieties of eggplant with minimal effort. Although eggplant seeds are tightly embedded in the flesh of the fruits, extracting eggplant seeds is fairly simple with the help of a food processor or a blender.
Eggplants, also known as aubergines or brinjals, are grown for their edible immature fruits. Varieties display a wide range of fruit sizes, shapes, patterns, and colors ranging from the elongated white fruits of ‘Casper’, to the shiny, pear-shaped, purple-black fruits produced by ‘Florida High Bush’, to the 2-inch-round striped fruits of ‘Lao Green Stripe’. The oval pale-green fruits of ‘Applegreen’, the long lavender eggplants of ‘Pingtung Long’, the diminutive ‘Thai Yellow Egg’, and the pink-and-white-skinned Italian heirloom ‘Rosa Bianca’ also lend colors to the species’ broad palette. The flesh color of these fruits can vary, too, from white to green, depending on the variety.
“Easter Egg” varieties were once thought of as a separate species, but they can cross-pollinate with other eggplants and are now classified as the same species. However, ‘Red Ruffled’ and other scarlet-fruited types (Turkish eggplant, Ethiopian eggplant, jiló) are a separate species, Solanum aethiopicum, and are not cross-compatible with garden eggplants. Typically eaten while its fruits are green and immature, Solanum aethiopicum bears fruits that ripen to scarlet. Its seeds can be extracted and processed in a similar manner to those of Solanum melongena.
Unlike the other cultivated crops in the Solanaceae, eggplants were not first domesticated in the Americas. In fact, the wild relatives of eggplant are present throughout Africa and Asia. Although there is still debate, many researchers now believe that eggplants were domesticated at least twice, once in India and once in China. Some researchers believe that the “Easter Egg” types of eggplant (Solanum melongena subsp. ovigerum) were derived from a third domestication event in Southeast Asia. Written records in both India and China indicate that eggplants have been used in these regions for at least 2,000 years. From India, eggplants traveled west on trading routes to Africa and the Mediterranean region. From China, eggplants traveled east to Korea and Japan. The Southeast Asian eggplants remained mostly localized in that region until the modern era. Eggplants were first introduced to Europe via Spain and Italy during the Middle Ages, but like tomatoes, they did not become a significant part of European cuisine until centuries later. Eggplants were first brought to the Americas by the Spanish in the fifteenth and sixteenth centuries but were not readily adopted as a food crop until later.
Growing Eggplants for Seed
Perennial in tropical and some subtropical climates, eggplants are frost sensitive and are generally cultivated as annuals in temperate climates. They grow best in warm climates with warm nights; daytime temperatures of 77 to 95°F (25 to 35°C) and nighttime temperatures of 70 to 80°F (21 to 27°C) are ideal for vegetative growth and fruit set. Eggplants grown for seed saving should be sown or, more commonly, transplanted at the same time and with the same spacing as when grown for eating. Eggplant varieties range drastically in height from 18 to 48 inches (46-122 cm) when fully grown. Large plants can be staked or caged like tomatoes. Eggplants can also be grown individually in five-gallon nursery pots or similarly sized containers. Seed maturity occurs after market maturity—approximately 50 to 60 days or more after pollination—and seed savers in northern regions should make sure there are enough warm days in the growing season for fruits to fully ripen.
Flowering, Pollination, and Seed Set
Eggplants either produce solitary flowers or small clusters of flowers, and each white or violet blossom is comprised of six fused petals. Eggplant flowers are perfect and are capable of self-pollination. The anthers create a ring around the pistil, but style length and stigma exsertion vary from cultivar to cultivar, influencing the likelihood of cross-pollination by insects. Eggplants typically continue to produce flowers and set fruits as long as environmental conditions remain favorable, but when fruits are allowed to reach seed maturity, the production of new fruits declines. Since it is always best to collect seeds from multiple plants, many gardeners meet both their seed and culinary needs by allowing a fruit or two from each plant in a population to ripen to seed maturity, while picking the remaining fruits for eating.
As a primarily self-pollinating crop with some frequency of cross-pollination by insects, eggplant requires an isolation distance similar to that of many outcrossing species. In the home garden, an isolation distance of 300 to 1,600 feet (91 to 488 m) helps to minimize the chance of outcrossing. Gardeners who exchange seeds with others or who garden in settings that do not provide many landscape barriers may choose to use the upper end of this range as a starting point when determining an isolation distance. Seed savers working toward the genetic preservation of a variety should consider using an isolation distance of half a mile (0.8 km).
If a sufficient isolation distance cannot be provided, gardeners who wish to grow more than one variety in the same season can easily produce true-to-type seeds by isolating flowers with blossom bags (p. 42). After successful fertilization, which is evidenced by the appearance of the developing fruits, the blossom bags should be removed to allow normal fruit development. Isolated fruits must be labeled at this point, so they can be identified later, when they are mature and ready to be harvested. If plants are grown only for seed production, and a large seed yield is desired, it is more efficient to build small cages or use row cover to isolate multiple plants than to isolate individual blossoms. Whether caging or blossom-bagging, it is important to harvest at least one fruit from each plant in the population.
Eggplant is self-pollinating, and viable seeds can be collected from just one plant. Although inbreeding depression is not generally a problem for eggplant, it is best to save seeds from multiple plants, especially if seeds will be shared with others. The recommended population size to help capture a variety’s genetic diversity is 5 to 20 plants. If genetic preservation is the goal, seeds should be collected from 50 plants or more.
When roguing or selecting, seed savers should consider important eggplant traits such as fruit color, pattern, shape, and size.
Seed Maturity and Harvest
At seed maturity, eggplant fruits generally change color; their original hues take on a yellow or brownish cast, and their glossy skins become dull. Ripe fruits easily separate from the plant when pulled. Individual fruits should be harvested as they mature. Botanically mature fruits can be held after harvest in a warm, protected location, allowing for the possibility of further seed development, but seeds must be extracted and processed before the fruits show any signs of rot.
Cleaning and Storage
Eggplants are wet-processed. In many varieties, the seeds are often concentrated near the blossom end of the fruit, and this portion alone should be cut into small cubes and pulsed in a food processor with ample water, using a dough blade to prevent damage to the seeds, until the seeds are dislodged from the flesh.
After blending, begin the decanting process by pouring the seed slurry into a larger container and adding even more water. Agitating the watery mash will dislodge seeds from the pulp and allow the viable seeds to settle to the bottom of the container. Repeated decanting should remove most of the pulp and any immature seeds; the mature seeds that remain can then be transferred to a strainer and rinsed with a strong stream of water. Immediately after rinsing, seeds should be spread in a thin layer on screens to dry in a warm, well-ventilated place. Small quantities of seeds can be dried on coffee filters.
When stored under cool, dry conditions, eggplant seeds can be expected to remain viable for four to six years.
LIFE CYCLE: Frost-sensitive perennial, typically grown as an annual in temperate climates
SUGGESTED SPACING: Same as when grown for eating
OTHER REQUIREMENTS: None
FLOWER TYPE: Perfect, self-fertile flowers are borne singly or in small clusters.
POLLINATION: Self-pollinated (autogamous) and insect-pollinated
MATING SYSTEM: Mixed mating system of self- and cross-pollination
ADDITIONAL CROSS-POLLINATION CONCERNS: None
FRUIT TYPE: Fleshy fruit (berry)
SEED MATURITY: Seed maturity occurs after market maturity. Fruits develop a yellowish or brownish cast and lose luster. Harvest individual fruits as they mature.
PROCESSING METHOD: Blend fruits, then decant.
EXPECTED SEED LIFE: 4–6 years
ISOLATION DISTANCE: 300–1,600 feet (91–488 m)
For Viable Seeds: 1 plant
For Variety Maintenance: 5–20 plants
For more on seed saving, see our Seed Saving Guide.
Reprinted with permission from The Seed Garden, by Micaela Colley & Jared Zystro, edited by Lee Buttala & Shanyn Siegel and published by Seed Savers Exchange, 2015. Buy this book from our store: The Seed Garden.