Everything You Need to Know About Hardening Off Seedlings

One of the biggest mistakes newbies make when it comes to starting their plants from seeds is to just throw them out into the garden without hardening them off first.  Hardening off plants is basically SLOWLY getting them used to the outdoors.  Plants started indoors have only known the minutely variable climate of the indoors.  They have probably had the luxury of a steady grow light, and have not had to withstand the afternoon sun, wind, or fluctuations in the temperature.  Hardening off is basically introducing them to the outdoor variables slowly, so that when it is finally time to plant, they have toughened up a bit.

How long you harden off your plants really depends on your location.  I usually harden mine off for about seven days, but here in Seattle, the weather is mild.  In areas with significantly cooler morning or nighttime temperatures, you may want to shoot for longer…say, like two weeks.

To start the hardening off process, scale back on watering, and stop fertilizing all together.  Set the seedlings outside in the shade for a couple of hours and bring them in at night.  Each day, increase how long you leave them outdoors and how much direct sunlight they are exposed to.  After several days {again, depending on how long you plan to stretch out the process}, leave the plants outside all night.  For me, this is around day seven.  Make sure to check nighttime temperatures, just to be safe.  If the nighttime temperatures are still too cold, it will be too early to plant your seedlings anyway.

Once your seedlings have spent a couple of lonely nights outdoors, you can go ahead and transplant them into the garden beds.  Make sure to water them in well.  You can also start back up on your fertilizer routine once they are transplanted {if you have a fertilizer routine–also, “fertilizer routine” makes it sound like you should have a musical number and a baton}.

It’s the worst to invest time and energy growing seedlings only to have them die after you plant them. Hardening them off is basically like a little insurance policy for your time and effort.

~Mavis