About a month to a month and a half before your last yearly frost date is a good time to start seeds indoors. Seedlings take up to 6 weeks to mature to the point that they can be transplanted outdoors. By starting seeds indoors, you can get the jump on growing plants that produce fruit, like tomatoes.
Many garden centers sell seed starter kits that are composed of a plastic “mini greenhouse” and seed starter mix in the form of compressed peat pellets. But you don’t have to buy these kits to start seeds. You can start seeds in found containers such as cardboard egg crates, paper drinking cups or folded newspaper paper pots. This year, I am using the leftover plastic plant packs that my pansies were sold in last fall.
To prepare paper cups or egg crates, punch a hole into the bottom of the container for drainage. Prepare a newspaper pot by folding a long section of a piece of newspaper over four times along its length. Lay an aluminum soda can on its side so that the lower 1/3 of the can overlaps the newspaper. Roll the newspaper around the can and tape the loose end down with masking tape. The can that you select will determine the width of the paper pot. If you use a skinny energy drink can, you will have a narrow pot.
Fold the lower end of the newspaper around the can’s bottom as if it were the end of a present and tape the flaps down with masking tape.
Fill your seed starter containers with a sterile potting medium such as peat moss. Make sure the peat moss is sterile before using it. Seedlings are kept in a moist environment that makes it easy for fungus to attack the plants once they emerge from the seed. Water the potting medium until it is moist, but not saturated.
To get an idea of what moist soil should feel like, take a dust cloth and soak it under your kitchen tap. Then squeeze the cloth until it no longer drips. Your soil should feel as damp as that dust cloth.
Use the point of a pencil to open a planting hole in the middle of the pot. Most seeds come with instructions on how deep that you should plant them. But a good rule of thumb is to place seedlings three times as deep in a planting hole as the seed’s width at the widest point.
Once the seed is planted, cover it with soil. Then cover the container with plastic food wrap and place it in a sunny windowsill so that the soil will warm up. The plastic wrap helps to hold moisture in and warm the soil so that the seedling will germinate. If the soil dries, the seedling may not germinate. You can raise the plastic as the seedling sprouts by creating a tent with chopsticks, pencils or toothpicks. Once the seedling begins developing true leaves, remove the plastic.
Keep the seedlings in a sunny, south-facing windowsill. Outdoors, most vegetables need at least 6 hours of direct sunlight to grow. Indoors, the plants will need bright, direct sunlight from a windowsill to make up for the lack of sunlight in the rest of your house. Because seeds grow toward light, you should rotate the seedling containers each day so that they grow evenly on all sides.