The key to having your plants in the right stage for planting outside is to count backwards. For example, if you want onion plants to put in the garden in early April and the seed packets indicates to plant them indoors six to eight weeks before outdoor planting time, then they should be sown indoors in early to mid February. If you want to plant outdoors in mid April, then delay sowing indoors by that same amount of time.
Do not start too early though. Some plants benefit from the very early start indoors. However, over long periods of time most seedlings will get too large and difficult to manage indoors. The idea is to time seed sowing so the plant can be moved outdoors to harden off without being held for a long time indoors.
Common vegetable plants that are easily started under lights include onion, cabbage, broccoli and cauliflower. All of these plants enjoy cold weather and can be planted in the garden early in cold frames or under hotcaps. Therefore, their indoor planting date is also early, about six to eight weeks before the outdoor planting date.
Tender vegetables commonly sown indoors include pepper, tomato and eggplant. These vegetables will not tolerate cold weather so their outdoor planting date is late May. Indoor sowing dates range from four to six weeks for tomato, to eight to ten weeks for eggplant. Counting backwards gives you indoor sowing dates of mid to late April for tomato or mid to late March for eggplant. If your target outdoor planting date is earlier, then start your seed the same number of weeks earlier as well.
Don’t use old seed. Seed is best stored under cool dry conditions. If you are working with seed found in a garage or storage shed, you may have very poor germination. Use fresh seed whenever possible; you will be pleasantly surprised at how well new seed germinates and grows compared to old seed. Only purchase as much seed as you need for a season or two and store leftover seed in a plastic food storage bag in the crisper of the refrigerator.
If you can’t bear to throw away a bag of seed packets, then test it prior to planting. Put 20 or 30 seeds on a damp paper towel. Fold up the paper towel and put it in a plastic bag. In a week to 10 days, check the seed to see how many germinated. This will give you an idea of how well the old seed would grow.
Most seed will benefit from heat provided to the soil. This “bottom heat” speeds up the process of germination and root growth. Select a warm area of the house to start the seeds. There are also very good, relatively inexpensive, heating mats for seed sowing available at local garden centers and through catalogs.
If you have never grown plants from seed, try it this year as a family project—starting a few of your own plants to grow fresh produce this summer.