Overwintering tender perennials and annuals.
An annual is a plant that has a one season cycle. It grows, blooms and dies off. No matter what zone you live in, it will not just keep going. Examples include impatiens and petunias.
A perennial lives on, year after year. Like animals, different species have different life spans. Some live for under five years, some last over a hundred years.
The term, tender perennial, refers to a plant species that is perennial in warmer zones, but will not survive winters below certain temperatures. Tropical plants can be perennial in Zones 9 – 11 and tender in Zones 8 – 5.
In deciding whether to overwinter a plant indoors, it is best to know whether the plant is an annual or a tender perennial. A true annual will not live on in your home, its lifecycle is over. Annuals are often sold in flats, whereas tender perennials may be sold in larger, individual 4” pots. Lantana and geraniums (pelargoniums) are examples of tender perennials; they can mature to have woody stems.
A tender perennial might live on indoors. It depends on how much heat, humidity and light you can offer. Can you duplicate the sunny outdoor climate of summer that it enjoys? If not, it may not survive a cool, dry home with low natural light. If your indoor conditions are not ideal, the plant is likely to succumb to pest and disease and might just linger in an unhealthy state. Plants take time to recover and to be slowly reintroduced back outdoors in spring. Is it worth the space, effort and anguish, when you can buy a healthy new plant from the nursery for $5?
If you have decided to overwinter a plant, the time to prepare it for its indoor life is a month before frost. If you are digging up a plant from a garden bed or repotting it from a container display, a month gives it time to recover from (effectively) transplant surgery. You would likely also be pruning and shaping it to keep it compact and tidy – more surgery.
Even an already potted plant needs to be pruned and made free of disease and pests. To break pest lifecycles and ensure that no larvae or eggs remain, pesticide may have to be applied weekly to every 2 weeks, depending on the lifecycle of the pest and the environmental conditions. Whitefly, aphids, mealy bug, scale and spider mites are the common indoor pests. Always follow pesticide use instructions and check validity of advice given in social media comments. Just because a lot of people say the same thing, doesn’t mean that it will work for you. Depending on your plant species, how you apply, at what temperature, how often and in what concentration matter to how well it will work.
If you are taking cuttings, you would have to know how long the cuttings take to root and allow that much more time.