Many gardeners let their houseplants hang out on the front porch to bask in the sunshine and soak up summer's humidity. As the temperature drops in the fall, it's time to prepare your tender plants and tropicals to overwinter indoors. Once the overnight temperatures start to dip near 50 degrees Fahrenheit, it's time to start the move. Most tropical plants and tender perennials will tolerate temperatures down to 45 degrees Fahrenheit, but it's best not to take a chance. Many tropicals will thrive happily indoors, but there are a few steps to ease the transition from outside.

Keep Only Healthy Plants

Did the plant struggle this summer? If so, you might want to cut your losses right now. If it did not thrive outdoors, the chances of the plant improving indoors are slim. The last thing you need is to bring a diseased plant indoors and threaten the health of your other plants. If you are attached to the plant, consider taking a cutting and propagate it over the winter.

Determine Where the Plant Needs to Overwinter

Make sure the room has enough light and humidity for your plants. Common houseplants can overwinter in a room that gets adequate sunlight. This is a great time to clean your windows to help maximize the amount of sunlight that comes into the room. If the room in which your plants will live during the winter does not get enough light, consider adding a full spectrum light on a timer to help supplement the sunlight.

How to Acclimate Your Plants

A sudden change from warm to cool or humid to arid can be traumatic to plants. This will lead to yellowing of leaves and die back. The transition from outdoors to indoors can put your plants into shock, so it is best to start this process slowly. Ideally, pick a spot away from heat vents and drafts. You can use a cooler room, like a garage or basement for a few days to acclimate the plant to the drier conditions indoors.
To acclimate plants, start bringing the houseplants inside at night for the first few days. Alternatively, you can plant the plants in a shady spot under a tree or on a covered porch for a few days to help it adjust to reduced lighting conditions. Move them back outside in the morning. Gradually, increase the amount of time the houseplant spends indoors until it is settled for the winter.
Potted perennials, trees and shrubs can overwinter in a garage or basement. They will enter a dormant phase and will not need as much sunlight and water during the cold months. Once the plants have died back and dropped their leaves, give them a good watering and place the potted plants in an insulated garage or basement. The temperature should not fall below freezing; a range of 32 to 45 degrees Fahrenheit is good. Check the plants periodically and only water if the soil is dry.

Destroy Any Pests Living on the Plant

Check the plant thoroughly for any signs of pests on the leaves, limbs or in the soil. Normal plant pests like mealy bugs and aphids are not that big a deal when the plant is living outside, but they can quickly turn into a serious infestation if they are allowed to overwinter indoors. An effective way to debug your plants is to submerge the entire plant in a bucket of water with some mild soap.

To Debug Your Plants:

  1. Get a large bucket or tub (large enough to hold the entire plant, pot and all)
  2. Fill the tub with water and add a few squirts of castile soap.
  3. Submerge the entire plant in the soapy water for 7 to 10 minutes.
  4. Remove the potted plant and rinse off any remaining soap off the plant.
  5. Let the plant drain outdoors complete before you bring it in.

Prune the Plant

Chances are your plants did plenty of growing over the summer. Go ahead and prune them back a bit, making sure to remove any dead limbs and leaves. If the plant has outgrown its pot or is root bound, this is a great time to re-pot the plant and do a little root pruning. If you do re-pot, try to use a container at least 2 inches bigger than the current pot; your plant needs room to grow.

Indoor Care

Once the plants are settled in your home for the winter, do not over-water. Over-watering is the primary reason indoor plants die. Due to the reduced lighting in the winter, houseplants do not need as much water. Only water when the soil is dry to the touch. To help raise the humidity around the plants, you can group the plants together. Another option is to place them near the kitchen or bathroom. If the air is very dry in your home, consider using a cool vaporizer or siting your potted plants on trays filled with pebbles and water.
With a few steps and some diligence, your plants will thrive and keep you company through the winter. When spring rolls around, you and your plants will be ready to get back outside and enjoy the warmth.