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Moving houseplants outdoors for the summer

Q: I’d like to move my houseplants outside during the summer. Is there any way to prep the plants or ease the transition?

Henry J. Haverford, Oneonta, NY

Photo/Illustration: Janet M. Jemmott

A: Tim Pollak, outdoor floriculturist at Chicago Botanic Garden in Glencoe, Illinois, responds: As the weather warms in spring, gardeners itch to take themselves—and their houseplants—outdoors. As eager as you both are to experience fresh air, soft breezes, humidity, and sunshine, take it slow. Plants must first be acclimated to the temperatures and light levels found outside. This process is similar to the hardening off of tiny greenhouse-grown seedlings before planting them in the garden.

Timing is everything. Most houseplants are native to tropical or subtropical areas and should not go out for the first time until night temperatures are consistently above 50°F. Others, like azaleas and oleanders, are tolerant of lower temperatures and can be moved out as long as there is no danger of frost in the forecast. To be sure, check the average last-frost date in your area. Here at the Chicago Botanic Garden (USDA Hardiness Zone 5b), for instance, that date is about May 15.

When moving plants outside, place them in a protected, shady location for the first 10 to 14 days. Be ready to bring them back in if night temperatures dip below a plant’s preference, whether it be 50°F or 32°F.

Check watering needs daily because soil dries out quickly outdoors. Gradually increase the exposure to light. White patches on leaves (sunscald) could indicate too much sun. If it’s not severe, the leaves will recover.

Even before moving the plants outdoors, several things can ease the transition. Repot the plant into the next larger pot size. Use a fast-draining potting soil or soilless mix, and water the plant well. Expose your delicate plants to higher light levels for a week or two while they are indoors. This can be as simple as moving them from an east window to a south window. If the plants need light pruning, sprucing up, or reshaping, now is the time. Also, hold off on fertilizing until they are actively growing again.

From Fine Gardening 109, pp. 24