Indoor Seed Sowing—Warm Season Vegetables

It’s officially the end of winter and the seed catalogs have been overflowing in my mailbox since the beginning of the New Year. “Sow” what are you going to grow? 

March signals the part of the gardening season when you need to start thinking about sowing some of your warm season vegetable crops. Most of these vegetables, such as tomato, eggplant, pepper, and basil can all be started in March and early April. In our area, these warm season crops will need to be planted out in the garden around mid-May, when the chance of frost has ended (referred to as the last frost date). Please see my chart at the end of this blog for general start times. Finally, remember that not all vegetable crops need to be started indoors. Beans, cucumber, lettuce, spinach, squash, melons, and watermelons are easily started by directly sowing seed outdoors.

If you are only growing a small amount of these indoor started crops, try recycling old grocery containers to use for starting your seed: egg cartons, milk cartons, plastic milk jugs, plastic holders for tomatoes and aluminum baking tins can all be used to hold potting mix and grow vegetable crops. If you are growing larger amounts consider purchasing seedling trays from a nursery.

Supplemental lighting will be needed in most situations for optimal growth. A fluorescent or LED shoplight works well for starting seedlings. The light should be positioned about two-to-four inches from the plants. If you do not use lightning make sure to grow your plants in your sunniest south-facing windows that you have. 

A good potting mix is also needed to ensure proper drainage—look for a mix at your local nursery that is labeled germination mix or potting mix. Mixing your potting mix with water before putting it in your seed-starting container is the easiest method, as this ensures the potting mix absorbs all of the water and distributes evenly throughout the mix. A five-gallon bucket works well for mixing smaller amounts. For even smaller amounts, a one-gallon zip lock bag works well. 

From this point you just need to sow your seeds. A pencil works well for making small holes in your soil. Remember to follow your seed packet instructions because some seeds need to be covered with soil and some do not need much cover at all. Keeping the tray moist during the initial stages is critical for germination. You can cover your trays with a clear dome lid to increase the humidity. Once the seeds have germinated remove the lid and keep the soil moist but not waterlogged. Bottom heat is also very helpful for getting your seeds to germinate—to utilize this method, simply put your seed trays in one of the warmer spots in your house.

As mentioned above, here are some typical start times that I follow for my warm season vegetable crops:

Sowing Schedule

Warm Season CropWeeks before last frost date (Mid May in SE PA)
Basil 8 weeks
Eggplant 8 to 10 weeks
Pepper 8 to 10 weeks
Tomato 6 to 8 weeks


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