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Sunday, February 26, 2012

Hardening Off Vegetable and Herb Seedlings

The process of hardening off your seedlings and soon to be transplants is to get them acclimated to the sun, temperature and weather. If you just put them out into full sun, they can get damaged. They can also get temperature shock.

I have a tendency to push things but I would recommended taking a at least a week to acclimate your plants to the outdoors. Believe it or not an hour of full afternoon sun can damage plants that have been grown indoors for weeks and weeks.  They have no sunscreen yet!

Get them out on full cloudy days if you can first. No sun. Just wind and clouds and typically cooler temperatures than your home. They can sit 6 hours outside if there is NO sun. Two days is a nice warm up.  Just get them out there before starting the sun routine. If you don't have a cloudy day to start that's okay.  I typically look about a week before I am ready to start the full transition outdoors. Typically there are cloudy days. Once warmed up... follow this:


  • Days 1-3: Morning sun for 1-2 hours
  • Days 4-5: Morning sun for 3-4 hours
  • Days 6-7: 5 hours of any sun


Don't leave them out overnight to freeze. This is for Zone 7 Maryland starting in March's sun and temperatures. You want a minimum of 50 degree days to avoid significant temperature shock.

My other tip is to put your whole seed tray out in the sun for 20 minutes whenever you can. Any time during the process of growing them indoors - get them some real sun and temperature. Do this as often as you can. It will acclimate them too and make for better plants. This 'toughens' them up and makes hardening off much easier.

Here is my parsley that was started in seed trays during the first week of January. They were out in the rain and are getting the cloudy day treatment. Believe it or not I am harvesting and using the leaves now.


Hardening Off Herb Plants (Parsley): Gary Pilarchik

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