If you are new to gardening you may not be in the know about hardening off. This is a reminder to amateurs and seasoned gardeners alike to please harden off your plants before you put them outside to enjoy the summer!
I was over at a friend’s house recently and she was proudly showing off her newly-planted vegetable garden. After telling me what each row would grow into she frowned and said “and these were the pepper plants I grew form seed indoors, and they just died when I put them in the ground.” I should have known what happened right away, but I have been out of the greenhouse for a couple of years now.
I first learned about hardening off the first spring I worked at Kingsbrae. It was the first warm beautiful sunny day, and I was cleaning in a room where we had stored some plants for the winter. These plants had a few windows and artificial lighting all winter. Since the floor really needed a wash I moved all the plants outside to a table in the sun thinking they would just love it. Well the Garden manager came along about 30 minutes later, explained what I had done wrong, and showed me the plants had been burnt by the sun. I was all done scrubbing the floor, so we moved everything back inside as he explained hardening off to me. Since it was early in the season, and they had only been out for 30 minutes, the plants would recover but not without some love and care. I had learned a very important lesson!
Plants grown inside or even in a greenhouse are not used to outside elements and direct sunlight. They need to be gradually introduced to the outside weather so they do no become shocked and die. This should be done over the course of a week or even more. Start by putting your plants outside on a warm day in a sheltered and shady location. Leave them out for no more than four hours then bring them back inside. Do this for three or four days, leaving them out an hour or two longer each day.
Now that your plants are used to the outside air they can handle dappled sunlight and a slight breeze. If it still getting cool at night be sure to keep bringing the plants back inside for the night. The next day you can put them in a location where they will get a few hours of direct sun light. Now, if the plants are sun lovers, they may be ready for direct sunlight all day. The process of hardening off really depends on the individual plant, but no plant should go from inside directly outside and into the ground.
If you have started vegetables inside, after a couple of days of hardening off you can set them (still in their pots) in what will be their permanent locations in the garden for a day or two before planting them in the ground. Also remember to ask, when purchasing plats from a plant centre, if they are ready to go in the ground or if they should be hardened off some before planting.
Gradually introducing your plants to the outside elements helps them strengthen their stalks and shoots to withstand wind and rain. Plants just like you can become sunburnt even if they are sun loving varieties, so be sure to work them up to direct all-day sun just like you would by building up a tan for the summer months!
During my four years as propagator I learned a lot about hardening off. Some plants would be ok if I put them outside on a warm rainy or cloudy day. Some would require more attention. It can be tempting on a beautiful sunny day to put your house plants out to get some sun, but beware! If you are unsure how tough your plants are always use the gradual approach to familiarizing them to the weather outside.
Jennifer Ukrainetz is a friend of Kingsbrae Garden and a frequent contributor.