How to Move Plants Back Outside
Bruce Black, Extension Horticulture Educator - University of Illinois
URBANA, Ill. – Plants, like people and pets, prefer a particular environment to perk up and be prosperous, according to University of Illinois Extension horticulture educator Bruce J. Black.
“In the spring, when you are ready to take your plants outside for the growing season, the plants are likely to suffer damage if they are not acclimated correctly to outdoor conditions,” explains Black. “Overwintered plants have become accustomed to indoor conditions and, like humans, adapt slowly to rapid changes in environment.”
Environmental factors such as light, wind, and temperature are some examples of changes to keep in mind. Each factor causes a different physiological response in the plant.
“Natural light intensity can decrease by up to 50 percent during the winter,” Black says. “Setting plants outdoors in direct sun without acclimating them to the increased lighting levels will cause scald or sunburn, which could lead to bleaching, browning, or necrosis (death) of the plant. Plant reactions depend on the amount of light the plant can tolerate.”
Indoor air tends to be relatively calm compared to outdoors, where plants will be exposed to wind. When plants are exposed to wind they become more rigid to support themselves. Too much wind can increase the rate of transpiration (loss of water through openings in the leaves) and may increase the rate of soil drying.
Most homes are kept at a constant temperature during the winter, between 68 and 75 degrees Fahrenheit, with a slight decrease at night. Outdoor temperatures fluctuate much more substantially. Plants not known for their cold tolerance (such as potted dahlias and hibiscus) can be injured if the low approaches freezing. Black advises that indoor plants should only be moved outdoors after the risk of frost is over.
“Before permanent placement outdoors, place the plants in a part-shade, wind-protected spot close to your home. Leave them in that spot for a few hours the first day, and gradually increase their time outdoors over a few weeks. This will allow the plants to begin to adapt to outdoor conditions,” Black says. “Gradually weaning your plants to the outdoors will give them a greater chance of thriving.
“Once they adapt to outdoor conditions, don’t forget to increase watering and fertilize occasionally as recommended,” he adds.