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Seed Starting 201 - Seedling Care, Light, Transplanting, and More

Our video on Seedling Care shows how Tricia grows her seedlings with proper light and fertilizer. Then she transplants her seedlings from trays to pots, and hardens them off before planting them outdoors. Here are more tips to help you grow strong seedlings and starts.

Light for seedlings

How much light will your seedlings need? Seeds have varying needs for light during their initial germination. Some seeds like to germinate in the dark (pot marigolds, verbenas), some are indifferent to light (hollyhocks, zinnias), and most need substantial amounts of light (lettuces, petunias). Depending on what seeds you're growing you can use a south-facing window, a fluorescent lamp, or a grow light as your light supply. Artificial light sources should be turned on 16 hours a day. If possible, raise the lights gradually as the seedlings grow.
Seed Starting Seed Starting
Seedlings with adequate light are upright with straight stems. Seedlings that don’t get enough light will be “leggy” and flop over.
The first pair of leaves you see are known as "seed leaves" or cotyledons. The second pair of leaves are the all-important "true leaves". Review our tips on damping off to keep that from killing your seedlings. Proper seedling care should keep damping off at bay. Once you have "true leaves" you can do all sorts of fun things like transplanting and fertilizing.

Transplanting time

Move the seedlings to larger containers after the first set of true leaves appears. If you've been growing in seed trays then move them into 3 or 4-inch pots. Ease the seedlings out of their cells with a Widger or similar tool, being sure to handle only the leaves and not the stems. Gently firm soilless mix around them in their new pots and water them carefully. Choose from our wide range of plastic or biodegradable pots for transplanting. If you're using Soil Blockers, put the small soil blocks into 4-inch soil blocks.

Fertilizing seedlings

After transplanting, the seedlings should begin a regimen of fertilizer. If you're growing organically we recommend Peaceful Valley Liquid Fish Fertilizer, Liquid Kelp,  Soluble Kelp Extract, or Maxicrop. TIP: One less thing to worry about -- instead of keeping a calendar of when to fertilize your seedlings, just use 1/4 of the recommended amount of fertilizer each time you water.

Hardening off

Before the seedlings can be planted outside (after the last frost) they need to be "hardened off" -- a process by which they are literally toughened up via lower temperatures and reduced water. The plants respond by producing firmer growth. You can see Tricia harden off seedlings in our Seedling Care video. Harden off your plants two weeks before you expect to plant them in the garden. Move the plants to a cool room (45°F to 50°F) if you want to harden them off indoors. The plants can harden off outdoors if you prefer, but you will have to be sure to bring them in if the outside temperature goes below 45°F, or on windy days. If you're hardening off outdoors, put the plants in a shady area and gradually increase the amount of sunlight they get each day. Whether indoors or outdoors, incrementally decrease the amount of water on the plants, but don't let them wilt. Enjoy the rewards of growing your own healthy seedlings and starts, and their bounty in your organic garden!


  • Deb, you should be able to transplant into the garden from those trays. You should go through the hardening off process before putting them out though. Also plant in the evening or early morning to avoid transplant shock. You can also try feeding them with a little liquid kelp to also help prevent transplant shock.

    Suzanne at GrowOrganic.com
  • Can I plant seedlings from the small 192 piece starter trays into the soil? I was told I could and tried it, but they did not grow. Did I need to feed them? Or is it really beneficial to prick them out into deep containers as I’ve done in the past with good results?

  • What kind of potting soil should I use when I transfer to 3”-4” pots? I’ve been using plain coco coir to start in. Is that enough combined with fertilizer once they get there true leaves?

  • What concentrations of your liquid fish and kelp feed do you recommend as you say 1/4 strength of what’s recommended?

    Thank you


  • Of your liquid kelp extract what strength do you recommend to feed the seedlings? I generally have ready 1 oz per gallon but above it says 1/4 strength.



  • Polly, you can use coco coir but you will need to fertilize them. You can just use a good quality potting soil that in not too rich and offers good drainage.

    Suzanne at GrowOrganic.com
  • Polly, you can use coco coir but you will need to fertilize them. You can just use a good quality potting soil that in not too rich and offers good drainage.

    Suzanne at GrowOrganic.com
  • JC for the liquid fish you can use 1 Tbs per gallon of water for watering your seedlings.

    Suzanne at GrowOrganic.com
  • JC, you can use about 0.5 Tbs of liquid kelp per gallon of water for watering seedlings

    Suzanne at GrowOrganic.com
  • Do you have to harden off seedlings if you grow them in a greenhouse before planting? Or can we just grow them inside until the outside temperatures even out… granted they are not rootbound?

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