Seed Starting 201 - Seedling Care, Light, Transplanting, Fertilizing & Hardening Off

By on February 24, 2011

Vigorous pea seedlings growing at a local, organic farm.

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”. 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 Extract,  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!


  Comments (6)


when will you spring catalog be out

Posted by Norman Carpadus on Feb. 25, 2011 at 2:56:35 PM


Our mid-spring catalog should be in your mailbox on March 11.

Posted by Charlotte on Mar. 01, 2011 at 4:34:00 PM


Thank you for this post!

Posted by Cindy on Apr. 10, 2012 at 6:30:54 PM

Cindy, Glad you like it!

Posted by on Feb. 07, 2013 at 8:07:32 PM


Hi Charlotte.  I need some guidance.  I started my very first batch of seeds a couple of weeks ago.  My little babies seem strong, are growing well…BUT, I have a problem born from keeping my trays in the garage until I could get a grow light.  My seedlings are VERY leggy.  Is there anything I can do to correct that?  Someone suggested replanting them but burying them up to the seed/true leaves, so that the leaves are a little above soil level.  In this a good fix to the problem?  Thanks for the help.

Posted by Dominic on Jun. 09, 2013 at 7:07:51 PM

Hi Dominic, Some starts, especially tomatoes, are fine to replant deeply in the soil. But most of your plants will probably do best to be re-seeded since your failure rate deeply planting will probably be quite high. 

There is still time to plant squash, cucumbers, melons, bean, corn and many other seeds directly into the garden.

Hope this is helpful!

Posted by on Jun. 10, 2013 at 11:21:05 AM

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