An old joke goes: "Why do you put your houseplants out for the summer? So I can slowly kill them all winter back in the house." Well, there is a certain amount of truth to that. We cannot always get them inside for the winter when we should, cannot always supply the right kind of light for all of them, and often watering them is not easy given plant sizes, various soil mixes, and humidity in the home.
You sorted them last fall, deciding which ones win the windowsill lottery and which ones go on to "a better place" – a.k.a., the compost pile. Those that made it indoors found warmth and sunlight. Those that hit the compost pile enter the world of dark, wet and cold to come back as organic matter to other plants in the yard.
If you're reviving them by putting them back outside on the patio or under the trees in a shady bed, now is the time to do some repotting, pruning, and cleaning so the better conditions outdoors allows for good recovery and growth before next fall.
Repotting allows you to cut away any dead roots, and replace the spent potting soil with a new mix full of nutrients. If you can repot using the same soil mix for all your houseplants, watering will be easier, at least from the soil mix perspective. Any new mix will typically drain away excess moisture better than the old soil mix that has broken down and contains dead roots.
If you have the room to encourage bigger plants, go up one pot size, but no more. Roots need to be able to fill the pot by summer's end. If you are at the maximum plant size now, clearing out the old dead or damaged roots allows for repotting back into the same pot with new soil mix.
Pruning consists of taking back any growth that occurred indoors over the winter. Very likely it is thin and spindly, having grown towards the light of the window. This kind of pruning also helps balance the remaining top of the plant with the remaining roots in the pot. For foliage, another expectation should be some leaf loss and perhaps some sunburn if put directly into full sun immediately. Leaves created in the winter indoors do not have any "sunblock" on yet. Best to set any houseplant out on a cloudy day if possible.
While you are cleaning, you get a chance to look at the overall condition of the foliage. Maybe the plants have great foliage making your job easier. If you have cats, then they enjoy a little taste testing and you will find holes and torn tissue. Some older, lower leaves facing away from window may have naturally died, pushing food into parts of the plant that can benefit from the sunlight, so that makes removing those leaves an easy choice. If you were lucky enough to have flowers in the winter from succulents, time to cut away the flower stalk.
Lastly, no fertilizer at first. Water and sunlight will be all that is needed to get those houseplants back on the survival road. Once you see new leaves emerge and mature, then fertilize with the product of choice. Feed them until July 4, then let them coast and slow down for that inevitable trip back inside the house after their summer vacation.
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.