As our good summer weather begins to wind down, it is time to get our vacationing houseplants ready to return inside for the winter. A few decisions can be made to save us some time. For many, we take them outside to let Mother Nature nurture them back to a better state of health, knowing that once back inside, they will be in a less than perfect growing location. You may have set them out on the ground under shrubs or evergreens, put them on the edge of the patio or next to the home. Since houseplants are not frost tolerant, the best practice is to get them acclimated to being indoors long before we have cool temperatures outdoors.
First, houseplants should be looked at carefully to see if you really want to bring each one back in the home. For example, some may have grown too big over the summer for their indoor spots. Seasonal plants, like the Poinsettia, that you nursed along may be good candidates for the compost pile, as getting them to re-bloom is difficult and you are likely going to get another one from someone anyway.
Once you know which ones are headed back indoors, it is time to clean them up. That includes removal of any dead foliage, picking the outdoor litter out that accumulated during the summer and, perhaps, the need to do a little trimming to make them more uniform.
The next step is to very carefully inspect them for insects. They have been outside awhile now so it is likely that they have been host to a variety of outdoor insects – sow bugs, spiders, earwigs, to name a few. A strong stream of water to both the top and lower leaf surfaces will take care of the bigger pests. Flushing the pot with lots of water will drive the soil insects out. If you find spider mites on any of the plants, a treatment with insecticidal soap or synthetic insecticide will be needed, with two or three repeated treatments to be sure the life cycle is broken. This is much easier to do now while outdoors than dealing with mites in the home later.
Almost done now. Houseplants in the full sun should be moved to a shady spot to start the acclimation process to lower light levels. The goal should be to bring in the plants before the furnace kicks on and before cold weather gets here. This can be done gradually, bringing in the more sensitive plants first and finishing with the hardier houseplants. Bring them in on the dry side and water them carefully as the need for water will be less as they get used to the lower light levels. Do not be surprised to see some leaves yellow and fall too as the change occurs. Set a date to be done so you are not scrambling after dark to get them into the garage the night of the first frost!
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.