How to overwinter tender perennials

Save your perennials for next spring with these simple steps

Many of our favorite garden plants are tender perennials. These plants have a perennial lifespan in locations with mild winters but cannot survive Oklahoma’s freezing temperatures. However, most can be easily overwintered indoors. Different storage methods are used depending on plant biology.

Plants that produce a bulb, corm or tuber can be dug and stored in a dormant state, as described below. Other plants can be kept as houseplants over the winter. This is the best way to store tropical plants such as tender agaves, tropical hibiscus, cordyline and more. Plants already growing in containers can simply be moved indoors, though you will want to check the containers for insects and other critters first.

Tender perennials growing in the ground can be dug and potted for winter. A few good candidates for potting include Joseph’s coat, Persian shield and cuphea. By the end of summer, these plants have likely grown rather large, so trimming and dividing may be necessary. You can cut the foliage and stems back by as much as two-thirds.

Garden soil is too heavy for plants in containers. When digging tender perennials, shake off all the soil from the roots and use a commercial potting mix in containers. You may need to trim the roots gently to fit them into the container. Place potted plants in the sunniest location you can find indoors. Keep a close eye on them for the first few weeks as they recover from trimming.

Tender perennials that produce a bulb, corm or tuber can be dug from the ground and stored in a frost-free location. These plants generally require darkness to help maintain dormancy. Some prefer damp and dark conditions for winter storage, while others thrive in dry and dark locations. For both groups, the ideal storage temperature is between 35-50˚F. It is important to avoid locations that experience freezing temperatures. Basements, root cellars, storm shelters, unheated garages and even a cool closet can work well.

To prepare plants for storage, dig them from the ground after the foliage naturally dies back or following the first frost. Brush away all soil and cut off foliage so just the bulb or tuber remains. These need to be cured before storage in a dry, well-ventilated area at room temperature. Cure bulbs for damp storage for a few days. Bulbs requiring dry storage should cure for 2 to 3 weeks. Only store healthy, disease-free bulbs. Discard any that are shriveled or discolored.

Many tropical and subtropical plants, including canna, colocasia (elephant ears), dahlia and caladiums, require damp storage to prevent the bulb from drying out. Our goal is to provide just enough moisture to prevent the bulbs, tubers and corms from drying out, but not enough to encourage rot. After curing, store bulbs on a bed of damp (not wet) peat moss, sand or shredded newspaper inside an ice chest, plastic bag or other container that will help retain moisture but is not airtight. Check bulbs regularly and mist lightly if the substrate becomes too dry. If you see moisture beading inside the bag, open it up to let it dry out for a day or two.

The easiest bulbs to store are those that require dark, dry conditions. These include gladiolas, freesia, crocosmia, mirabilis and others. After curing for 2 to 3 weeks, store these in onion sacks or paper bags. Then, wait for spring to return. Don’t forget to label your bulbs, as it can be difficult to identify varieties from tubers.