"Rosa Bianca" eggplant (Solanum melongena "Rosa Bianca") has the traditional oblong shape of an eggplant, but instead of uniform dark purple skin, this cultivar is streaked with light violets and cream tones. "Rosa Bianca" eggplant seeds germinate reliably in the right conditions, but if you keep ending up with empty seed flats and garden beds, it's time to turn detective and figure out why your "Rosa Bianca" seeds won't germinate.
Old Seeds Don't Germinate
When you buy seedlings, local availability limits your choices, but when you buy and plant seeds you can order some of the obscure and delightful eggplant varieties available. If you've planted eggplant seeds and they aren't germinating, make sure you're not trying to grow old seeds. Eggplant seeds remain viable for only four years. If your seeds have been kicking around the garden shed for a few years, replace them with fresh seed.
"Rosa Bianca" seeds won't germinate in cold soil. The seeds require a minimum temperature of 60 degrees Fahrenheit to germinate -- but that's the absolute minimum. A range between 75 and 90 F is optimal; above 95 F, it gets too hot for the seeds to germinate. The ideal soil temperature to stimulate eggplant seeds to germinate is 85 F. At this temperature, you can expect germination within a week to 10 days.
Control Soil Temperature Indoors
When you start seeds indoors, you can control the soil temperature. "Rosa Bianca" eggplant seeds respond well to bottom heat. If you've struggled with getting the seeds to germinate, try placing a seed-heating pad under the seed flat. Make sure the one you use will heat the soil to 75 F or above. When you start seeds indoors, you can improve germination success by using sterile seed-starting mix rather than potting soil or garden soil.
Keep Seeds Near the Surface
Seed germination success depends on the combination of moisture, temperature and light. If you plant too deeply, the seeds will fail to germinate in the dark soil. Plant "Rosa Bianca" seeds 1/4 inch deep and cover them loosely with soil or seed-starting mix. When you water, just mist the top, rather than directing a strong spray at the seed flats; otherwise, you could actually push the seeds too deeply into the soil with the water.
Direct Seed in the Garden
Unless you live in a warm climate, start seeds indoors six to eight weeks before the last spring frost date in your area. Eggplants, including the "Rosa Bianca" cultivar, need a long growing season, between 100 and 150 days above 70 F when you start them from seed. In warm climates, you can plant seeds right into the garden bed. Just wait until all danger of frost has passed and the soil has warmed to at least 60 F.
Taking Care of Seedlings
During germination, "Rosa Bianca" seeds don't need any fertilizer. The seeds contain enough nutrients to support germination and the first stages of development. The seeds do need consistent moisture. Mist the soil whenever it starts to dry out and make sure it's damp all the way through. If seeds dry out they won't germinate, and you'll end up with an empty seed flat or garden bed.