Bringing Plants Indoors for the Winter

When the night temperatures start to edge toward the frost mark, the time has come to prepare them for the trek indoors. For many of us, indoor space is very limited, and the decision must be made on which plants to overwinter and which to discard. Many of us have started to use tropical plants in our patio containers, and these plants need bright light to thrive through the winter indoors. In some cases, especially if space and light is limited indoors, it is best to discard your annuals and purchase new plants the next year.

Canna and elephant ear are fairly easy to over-winter. After the first frost, dig them and cut back the tops. Do not divide the rhizomes at this point as the fresh cutting may rot through the winter. Store the rhizomes in peat, vermiculite or sand in a cool, dry location with temperatures no lower than 40 degrees. In spring, cut the rhizomes into pieces with several growing points each and start them as you would new rhizomes. These plants are best when started in early March as this gives them enough time for nice growth before placing them outdoors in the spring. Many people over-winter these plants successfully as house plants, myself included. I find it easier to move the pots indoors, and give minimal care throughout the winter, moving the pots back outdoors during the spring. They can easily go many weeks without water through the winter months, and can be cut back severely to reduce size if space is a limiting factor. Banana plants over-winter wonderfully as house plants, and they can be cut back completely when bringing indoors.

Tuberous begonias and caladium are also easy to store over the winter. If the tuberous begonias were grown in containers, these plants can be brought in for winter enjoyment and treated as a houseplant. If planted into the ground, dig up the tubers carefully after the first light frost and remove the top growth. Leave the soil and roots around the bulb intact and place the bulbs in a cool, dry area for 2-3 weeks. Then, remove the soil and remaining roots that should be shriveled by this time and pack the bulbs in peat, sand or vermiculite to prevent excess moisture loss. As with cannas, store in a cool 50-55 degrees and be sure the bulb aren’t subjected to freezing temperatures.

Gladiolus also need to be dug and stored at temperatures above freezing for the winter months. Gladiolus develop from a corm, which is an underground stem. Once the foliage is yellowed, these corms can be dug from the soil and the foliage removed. The corms should be allowed to dry for a week before being placed into old onion sacks or nylon stockings where they can be stored in a cool, dry location at about 50 degrees until time for planting.

Many people like to over-winter geranium plants and there are several techniques that people have success with. Be sure to get the geranium indoors before the first frost, otherwise the plant will freeze. Some hang geraniums by the roots in the basement or any other cool location. If the basement is quite cool, this will be successful, however, temperatures must be around 40 to 50 degrees to prevent plants from drying out too much. Plants should be dug up and have the excess soil removed from the roots, then cut back by about one-half before hanging them. To over-winter my geraniums, I treat them as houseplants. Before I bring them indoors, I prune them back by about one-third its original height. I then keep the plant in a sunny location and allow the soil to dry out in between watering. Many years I take fresh cuttings and discard the old plant. These slips should be four to six inches long and be taken from the healthiest stems. I remove the leaves on the bottom 2 inches of the cutting and leave overnight for the ends to dry out. I then stick the end into well-drained potting soil and water heavily. Once new growth appears, I fertilize monthly and keep the soil evenly moist, and locate in a sunny location. Whether I root new plants or bring the original plant indoors, I pinch regularly through the winter to promote heavy branching.

Hibiscus are ideal for use as houseplants. Hibiscus will bloom throughout the winter if kept in a sunny window. If you cannot find a warm, sunny location for them, they can be put in a cool place with moderate light where they will become somewhat dormant and drop leaves. During this period they should be kept slightly moist, but do not over-water.

Whatever plants you bring indoors, it is important that you take precautions so you don’t move insects into your house and contaminate other houseplants. Carefully inspect the plants for insects that will proliferate in the warm, dry conditions indoors. If insects are found, it is a good idea to spray the leaves thoroughly with an insecticidal soap or spray with a pesticide approved for use indoors. As you move the plants indoors, isolate them from any other indoor houseplants for approximately two weeks to ensure you don’t contaminate other houseplants.

Mary Kroening, Horticulture
573-882-9633