Steve Reiners, professor of horticulture at Cornell University, says now is the time to start planning for indoor plantings if you want to prepare transplants for your vegetable garden this year.

Reiners says:

“One of the biggest mistakes gardeners make is starting their transplants too early. This table provides some guidance on when you should start your transplants. It assumes a last frost date of May 20.

“There are other important factors when it comes to transplants – lighting, temperature, soil, and containers. The most important is light. Even a sunny window facing south will not provide enough light both in quantity and quality to raise healthy transplants. You can create a light box with fluorescent lights suspended about 4 inches above the plants.

“Most seeds don’t require light to germinate so you can put your containers in a warm, dark place after seeding them. Then move them under the lights and dial back the heat once the seeds sprout. You can buy electric heating mats that will warm your containers, soil and seeds from the bottom.

“For the soil, it’s best to use a good quality, already prepared sterile media that can be purchased at any garden center. These are typically prepared with peat moss and other materials such as perlite, lime, and a little fertilizer. Don’t use soil from your garden as it may contain some plant diseases and won’t drain well, making your seeds vulnerable to rotting in soggy soil.

“You have lots of choices for containers. I prefer to use plastic cell-packs as they can be washed and reused for many years. But you can use paper or Styrofoam cups, egg cartons, and pots made of peat moss or composted manures. Whatever you use, make sure they have holes in the bottom so excess water can drain out.”