Some plants require a head start indoors to ensure they’ll reach maturity during our growing season. Starting seeds can be easy and inexpensive; just follow our lead!
1. Assemble the equipment for starting seeds.
- Lights: Seeds need 12 to 16 hours of light a day. Hang a shop light on chains above the shelf where you’ll start your seeds. Use one cool-light and one warm-light fluorescent tube, and plug your light into a timer to ensure your seedlings get all the light they need.
- Containers: Choose from flats, old nursery containers, leftover yogurt cups, or pots you make from newspaper. If you’re using old containers, first wash them in a 10% bleach solution. For this tutorial, we’re using the APS system from Gardener’s Supply, which has a water reservoir on the bottom.
- Plant labels: It’s tough to tell young seedlings apart. Be sure to label yours with the variety and the planting date.
- Seeds: Seed packets will tell you when to plant indoors. They usually say something like “start six weeks before frost-free date.” Here in central Indiana, the frost-free date is around May 12. Or see this chart from Purdue University Cooperative Extension Service for planting dates.
2. Wet your seed-starting mix.
Seeds need something that is light enough to break through easily and porous enough to hold water without waterlogging the plants. Buy a “soil-less” mix designed especially for seed starting, and get one that does not contain fertilizer.
If you can find it, use coconut coir for an eco-friendly alternative to peat-moss-based mixes.
3. Fill your containers.
If you’re using a system that has reservoir, soak the wicking mat in water, then lay it under the seed tray with one end hanging into the water reservoir.
Fill your containers 3/4 to nearly full with the seed-start mix. Pat the mix down firmly to get rid of air bubbles.
4. Plant the seeds.
Read the back of the seed packet to determine how deeply to plant your seeds.
Make a small impression in the seed starting mix with your finger, then drop one or two seeds in the hole. Cover the planting hole with seed starting mix, then pat down firmly. Seed germination depends on good contact between the seed and the starting mix.
5. Cover the flat.
Cover with a clear lid or plastic wrap and place under the lights. This clear layer creates a greenhouse effect, warming the soil.
You may choose to put your seed tray on a heating mat to help seeds germinate, but ours seem to do just fine without extra heat. The trapped light from the shop light is enough to warm the soil mix to the 70 to 74 degrees most seeds need.
6. Watch them grow.
Once your seeds have sprouted, take the plastic cover off.
Set the timer on your shop light for 12 to 16 hours of light a day. Keep the light at about 2″ to 3″ above the seed tray, and raise the light as the seedlings grow.
Water your seedlings about every three days. Bottom watering is the easiest way. Mist your seedlings too, to keep the soil surface moist but not wet.
7. Keep them healthy.
Your seedlings will first put out a set of leaves call cotelydons. These look almost identical on all plants, which is one reason you need to label your seedlings.
After the cotelydons have shown up, your plants will put our their first set of true leaves—those that look like the leaves that a mature plant has.
Once you see the first set of true leaves, start feeding your seedlings once a week with a gentle compost tea or a liquid fertilizer at half-strength.
Thin out seedlings so you have only one plant in each cell or container. Use a pair of nail scissors to snip the extras off at the soil line.
Head off fungus attacks on seedlings by steeping one chamomile tea bag in a quart of water, cooling it, and misting your seedlings. A fan moving on low speed can also help prevent fungus attacks.
8. Plant them out.
Once the weather warms up, you need to harden off. Take plants outside for a few hours each day, leaving them in a sheltered place. Gradually increase the amount of time they spend outside for about a week; by the end of the week you should be leaving them outside over night. Keep the soil moist during the hardening off process.
(If you have a cold frame, you can just place your plants in that and leave them there to harden off. Be sure to open the frame to let heat escape on sunny days.)
Once your plants have acclimated to the weather outside, you can safely plant them into their permanent new homes.