Tips for overwintering annuals, tender perennials indoors

By Marilyn McKinley

OSU master gardener volunteer

My grandma brought so many plants inside for the winter: impatiens, begonias and geraniums bloomed all winter, beautiful Boston ferns were in several rooms. She said the best way to keep nice flowers is to ignore them. I suspect she knew just when and if to water and which window gave the best light. I have never had her luck with “winter” houseplants. Here’s some hints to keep have blooms all winter.

Perennials that survive Northeast Ohio’s winters are considered hardy. Many plants we consider annuals are perennials in their native habitats. Snapdragons, salvia, begonia and geraniums are examples. Knowing the climate types they prefer will help you to successfully overwinter these.

Many plants prefer sunny and warm conditions provided by south- or east-facing windows. Temperatures should be 60-70 degrees. The cooler the temperature, the drier the soil should be. If plants become spindly with thin leaves, add supplemental light or move to a southern exposure. Other common “annuals” that prefer sunny, warm conditions are coleus, begonia, impatiens, lantana and hibiscus, as well as succulents such as aloe, jade and kalancho.

By contrast, some tender perennials like sunny and cool. These are plants of the Mediterranean: rosemary, pomegranate, citrus and silvery plants such as lavender. Oleander, gardenia, fuchsia and hibiscus do well under these conditions, but growth will be much slower than if exposed to sunny and warm conditions.

Dark and very slight dampness are preferred by a few of our favorites. These plants are “resting” during the winter. Those with tubers (dahlia, cannas and sweet potato) are examples. Store these in a cardboard box or bin with newspaper or peat moss. An unheated cellar, garage or crawl space usually works well. Temperatures should be between 40 and 50 degrees.

Plants that are dropping their leaves may be too cool or getting too much water, although the normal adjustment from high light to indoor light may be the cause, so keep an eye on them and adjust conditions as needed. Some woody plants such as lantana, butterfly bush, fig and angel’s trumpet normally lose their leaves during the winter. Those plants can be reshaped, left in the pots and kept barely moist until new growth appears in the spring.

For help growing your perennials as houseplants inside this winter, go to: http://go.osu.edu/houseplantdr.