After spending $15 or more on a single annual (for me it was elephant ears – Colocasia esculenta ‘Black Ruffles’), it can be disheartening to dump it at the end of summer. Fortunately, there are other options.
Many annuals can be brought indoors and grown as potted houseplants. This must be done before temps drop below freezing (though Gerbera daisies can handle a light freeze).
If the annual is currently in a pot, cut off dead and dying leaves, gently remove spiders or insects – praying mantis, katydid, etc. – then drench the soil with insecticidal soap. Make your own insecticidal soap with a solution of 1 teaspoon dishwashing liquid to one cup of water. I spray leaf surfaces with the same solution to kill any whiteflies or other tiny hitchhikers.
Place the pot in a brightly lit area of the house. I have big windows with a lot of light; fluorescent lighting is advisable when sufficient natural light is unavailable. Keep pot(s) separate from other indoor plants for a few weeks.
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Annuals in the ground can be dug up – be sure to get as much of the root system as possible – and placed in a pot with houseplant potting mix (no garden soil as it contains all kinds of things we do not want in the house, plus it doesn’t drain well in pots). Before digging up the plant, cut the top back for easier handling. Do the same insect removal and spraying as noted previously.
Elephant ears can be overwintered as described above. An alternative is to wait for a light frost to dispatch the top of the foliage, then dig up the tubers. Cut off above-soil plant material, dry completely, then brush off dirt and store in peat moss in a dry, cool, above-freezing location (ideally not below 45 degrees). Avoid placing in airtight containers because moisture can build up and rot the tubers. I wrap mine in newspaper and keep in the garage next to the warmest house wall. (Most years, this option works; last winter was too cold for them to survive in the garage.)
The same cut-and-store approach also works with tuberous begonias, canna and dahlia.
Take cuttings to save coleus, fuchsia, impatiens, annual vinca and geraniums for next year. Take a 3- to 6-inch cutting from the top of the plant. Remove the flowers and bottom half of foliage. Dip the cut end in rooting hormone, if desired. Place cutting in moist perlite, vermiculite or lightweight, well-drained potting mix, then position in a bright location away from direct sun. Keep mix lightly moist but not soaked. In three to four weeks, you can plant rooted cuttings in small containers with houseplant potting mix and move them to a sunny location (or under fluorescent lights) to await their return outdoors in spring.