Knowing how to overwinter tender plants can protect them from freezing temperatures, save you money on purchases next spring, and give you the pleasure of keeping houseplants during the cooler months. Depending on the type of perennial and your conditions inside, you can either grow them as a houseplant, keep them in a dormant state, or dig them up and preserve their root bulb. Whatever method you choose, you’ll be surprised at how easy it is to overwinter your favorite annuals and tropical plants.
Option 1: Bring Them Inside as Houseplants
Many plants that we treat as annuals would be perennials in warmer climates. Begonias, bougainvilleas, citrus, crotons, geraniums, hibiscus, impatiens, rosemary, pentas, and tarragon are just a few of the many species. They won’t survive winter in Allentown outside, but we can easily dig them up in the fall and keep them as houseplants until spring.
It’s best to uproot before the first frost. Then check carefully for pests and pot them in fresh soil. Begin a gradual transition indoors, hosting them overnight at first and adding a few hours to their stay every day after. This slow adjustment gets them comfortable with the new digs, rather than stressing them out with a sudden move.
Once inside, you’d ideally set them up near a big window. If you notice them stretching towards the glass after a while, it’s a sign they need more light. Grow lights are a cheap and easy fix. If humidity is lacking, mist them occasionally or place a pan of water among the pots. Generally, they’ll need less water over winter, but that depends on the temperature and dryness of your home.
Option 2: Let Them Go Dormant and Store in a Cool, Dark Place
Many of the plants mentioned above go through a dormant phase during the dry months, even in tropical regions. If you don’t have enough space to keep plants near a warm window, you can ease them into dormancy and let them sleep in a cool, dark room. To put them to bed, the trick is to taper off their water supply in the fall and let them experience a frost. Then you can dig them up and place them in open boxes for storage. The leaves will fall off, but they should happily go into hibernation. Check them for moisture over the winter and water sparingly if they dry out too much. Any dark corner of a garage, basement, or root cellar in the range of 40-55°F makes a great storage place.
How to Store Tender Bulbs: Keep Them in a Cool, Dark Place
Some tropical and subtropical plants grow from a root bulb or tuber. Rather than letting them freeze and die in the ground, you can dig them up and store them in a dark root cellar, a cold part of your basement, or an unheated garage as long as the temperature is 35-50°F.
Some bulbs have more moisture content and need to maintain it overwinter. Cannas, dahlias, caladiums, and elephant ears are among this type of bulb. After a light frost has killed their leaves, dig them out of the ground, trim off the foliage, brush away excess dirt, but don’t wash them. Cure them in a dry location out of direct sun for a few days. Then, transition them into a bucket of sand, peat moss, or wrap them in moist newspaper and place them in an open plastic bag. If you seal them in, the trapped moisture will eventually cause rotting. Check them periodically to see that they are not drying out and adjust moisture levels as necessary.
Other types of bulbs are like onions: they require dry conditions to overwinter successfully. These include crocosmias, four o’clocks, and sword lilies. How to store them? Dig them up after a frost, trim off the dead foliage, and brush away excess soil. Then you need to cure them in a dry location at room temperature for 2-3 weeks. Afterward, you can place them in a breathable bag in a dry, dark room between 35-50°F. Just like a potato, exposure to light may cause bulbs to sprout prematurely.
Some tender perennials whose natural growing region is not far from our own may be able to overwinter right in the ground, as long as we cover them with a generous layer of leaf mulch, straw, bark mulch, or wood chips. If you have any questions about particular plants, feel free to call us or drop by our garden center!