It can take two weeks to 'harden' a plant
Q. What does hardening off really mean?
A. BABY, it's COLD OUTSIDE!! The frost free date in our area is mid-May so the beginning of May is a good time to begin thinking about hardening off plants.
Hardening off plants is the process of getting indoor plants accustomed to outdoor temperatures, seven to 14 days before transplanting them, by gradually exposing them to new light sources, temperature variations and water amounts.
Just as we do not appreciate that blast of cold winter air in our face, plants are very sensitive to the "shock" of being moved from that cozy warm indoor environment to the harsh outdoors!
The biggest shock is the significant increase in light intensity outdoors. Outdoor light can be as much as 100 times brighter than indoor light. Start placing plants outside in a shady area to avoid the midday full sun exposure for one or two hours a day for the first two to three days.
Wind is a danger to plants accustomed to the house or greenhouse as it dries out a plant very quickly and can cause them to snap or be knocked over. Place plants in a sheltered area and bring them back indoors for the night.
Keep in mind plants are living in a 60- to 70-degree environment and if they are then placed in near freezing temperatures that will kill your plants. After seven days, your sun-loving plants should be ready for temps above 45 degrees. Bring them back inside if it is below 45 degrees.
After seven to 14 days, plants are ready for transplanting. However, remember to not force them into drastic conditions to which they are not accustomed. Make sure the soil has adequately warmed for planting. Soil temperatures between 50 and 60 degrees are necessary.
Transplant them in the evening or a cloudy day. Water them immediately after transplanting and continue to monitor the watering as they will be actively growing and requiring more water and nutrients than they did indoors.
Too much stress can cause injury or death to the plant in addition to making them more susceptible to pest problems. Acclimate those transplants, seedlings and houseplants to their new environment and they will be growing abundantly in your garden.
- Bev Krams
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.