You should be seeding tomatoes about 6-8 weeks before you transplant them into outdoor soil, so for target date of May 15, I have to start at beginning of April.
Place seeds in shallow depth, in the small, drained containers, with room temperature, moist soil, assume 70-80% germination rate. They will take up to 2 weeks for germination. Control humidity with plastic, but allow some airflow.
As soon as the seeds germinate they will need plenty of the sunlight. If you are using a full-spectrum lights make sure you have them on about 16 hours a day.
Don't worry too much about selection of tomatoes, plant as many varieties you can and keep in mind that if you are planting for your local consumption:
- tomatoes don't need to be shipped across the country, so they don't need to tough skinned
- tomatoes don't need to "survive" a week before being placed on the store shelf, so they don't need to be rot resistant
- tomatoes don't need to be a size of pumpkin, because they are not for (freak) show
However tomatoes need to be:
- tasty to you
- right size for you to eat
- adaptable to your soil
- adaptable to your micro flora and fauna
Based on this two sets of criteria almost all of the heirloom and hybrid varieties today will NOT be suitable, so you have to find your own favorite by TRYING and SAVE THE SEEDS.
Resources:
http://www.wisconline.com/almanac/gardening/springfrost.html
