Winter brings low humidity and light conditions that are hard on indoor plants. The good thing is that not all is lost if your houseplants look like they are dying. You can do a few simple treatments for your plants to revive them when they are struggling during the winter season.
Washing the plant leaves works on most houseplants, except African violets. This treatment will remove dust from the leaves and give the plants a dose of humidity and moisture. Washing will also flush excess salts from the soil if your water is high in sodium. Remove the plants from their drainage plates and set them in a large tray or in the bathtub. Spray the plants generously with water using a watering can with a rain trickle topper. Use caution so you do not damage the leaves with a hard stream or wash too much soil from the pot. You want enough water so it drains from the bottom holes in the pot. Wipe leaves that appear dirty with a soft towel to remove built up dirt. Let excess water drain from the pots before removing them from the tray.
Fertilize your plants with a houseplant fertilizer diluted to one-half strength. This will give the plants a boost of nutrients that will help them grow and thrive during the winter season. Make sure to use a fertilizer formulated specifically for African violets and orchids when feeding these plant types. A once a month application of fertilizer diluted to half strength is acceptable for houseplants. Orchids will tolerate one-quarter strength fertilizer applications with each watering.
Winter is the best time to repot overgrown or container-bound plants. You may need to divide these plants if the root mass is too large for a container. Dividing plants is easy if you remember to make sure each root section has a portion of the main crown and a minimum of three growth nodes. Remove any roots that appear dry, soft or rotten. Choose a container that has 2 to 3 inches of space between the root mass and edge of the container. Repot the plant with soil specified for houseplants.
Set a humidifier in the room with your houseplants to increase the moisture level around the plants. Another option is to set the houseplants on a tray filled with stones and a layer of water. Make sure the containers are set above the water and not directly in to prevent too much moisture in the soil. You want to increase the moisture around the plant, not in the soil. Remember to rotate your houseplants every two weeks, or at the time of each water application. This will limit crooked stems from the plants trying to grow towards the light source.
These simple steps will help your houseplants thrive, even during the winter season when most plants go dormant.
University of Nebraska, Lincoln: Winter Care for Houseplants
University of Illinois Extension: House Plant Care