How to Start Seeds Indoors

Garden while the snow still flies by starting seeds indoors. You’ll save money (seeds are much cheaper than plants), have more choices and play surrogate Mother Nature to new life.

By

Gary Thompson

Updated on February 25, 2023

If grade schoolers can get beans to sprout using wet paper towels inside foam cups, you can do this.

The Simple Guide to Starting Seeds

Find Your Date Online

Your area's average last frost date determines how long your plants need to grow before moving outdoors. Find the date, then count backward on the calendar using the seed packet's suggested head start.

Chives, leeks, onions, pansies, poppies and snapdragons are typically started 12 weeks before the last frost. Ten weeks before the last frost, you can start most celery, kale, black-eyed Susans, delphiniums and impatiens. Eight weeks before last frost, start peppers, eggplants, tomatoes, alyssum, phlox and salvias. Six weeks in advance of the last frost, try seeding broccoli, cabbage, cauliflower, cosmos, globe amaranth and sunflowers. And three weeks before the last frost, seed cucumbers, okra, melons, squash, pumpkins, marigolds, morning glories and zinnias.

Let There Be Light

Seedlings need several hours of light per day. A sunny window works for a few pots or trays, but for high-volume seed starting, get fluorescent grow lights with timers.

Take the Temperature

Use a thermometer to ensure the room meets the ideal range listed on the seed packet. A light breeze from a small fan helps ward off disease that can kill seedlings.

Keep Hydrating

If you're not using a self-watering system (a refillable reservoir placed under the pots or trays), a spray bottle works well for gently moistening plants. Caution: Newbies tend to overwater.

Give Them Room

Seedlings outgrow their nurseries. When they're about 2 inches tall, transplant them to larger individual containers filled with regular potting mix.

Now For the Hard(ening) Part

A week or so before it's time to safely plant outside, "harden off" seedlings. Place outside in a protected spot for an hour or two each day, gradually increasing exposure. Some cold-tolerant varieties can be planted outside before the last frost.

Step-by-Step Guide to Growing Seeds

1. Fill 'er Up

Use a seed-starting mix. Most potting soil is too rich and doesn't drain well enough for seeds.

2. Make a Hole

Poke a seed hole in each cell (a pencil works well). Check seed packet info for the right depth.

3. Get Sowing

Drop two seeds in each hole, in case one fails. If both seeds sprout, you can snip one out later.

4. Top It Off

Add a thin layer of mix to cover the seeds, but don't pack it down. Mist lightly with water.

5. Make Identification Markers

It's easy to forget which seeds you planted where, so make little ID tags for each pot or tray.

6. Seal the Deal

A plastic cover creates a warm, moist environment while letting in light, like a greenhouse.

Consider Peat Pellets

Peat pellets (also known as seed plugs) provide a less-messy option to filling dozens of tiny pots or trays with loose seed-starting mix. The pellets come as mesh-covered discs that fit in a standard plastic tray and expand to a perfect seedling size when you add water.