Never say die: Overwintering favorite plants

Store begonias as tubers or take cuttings.                     Proven Winners

Store begonias as tubers or take cuttings.                     Proven Winners

As fall arrives, it may seem that puttering around with plants is about to come to an end and all of those specimens that can’t tolerate freezing temperatures are headed for the compost heap.

Not so fast.

Many of the plants we’ve enjoyed outdoors in fine weather can come in from the cold and live to play another day. Broadly speaking, these tropical or semi-tropical plants that can be kept on as houseplants and tender bulbs, corms and tubers that can spend the winter in a frost-free spot, sleeping the winter away in a dormant state. With a little forethought, you can keep your fingers in the dirt and your inventory of tender plants intact through the cold months.

Today we like to push the climate envelope. Our patios and decks overflow with container plants from warmer zones that grow year-round in their place of origin. Most houseplants, for instance, are tropical species transplanted to our homes.

Many gardeners like to give their houseplants a vacation outdoors where they benefit from the sunshine and humidity. Few plants really enjoy the dry atmosphere of air conditioned interiors and would just as soon spend the summer in the fresh air. Foliage plants like philodendron, jade plant and ivy and flowering species including Christmas cactus, cyclamen and orchids can make impressive growth in balmy outdoor conditions.

With these, the main concerns are to help plant make the transition back inside and to make sure they don’t bring along unwelcome insect hitchhikers. A careful inspection of all leaf surfaces is in order and it’s not a bad idea to tip the root ball out of its pot to hunt for soil-borne pests.

Moving houseplants into a shadier, dimmer spot for a few weeks can help them adjust. Just be alert for killing frost, which generally arrives in mid to late October. Once inside, where air is less humid, plants often drop some leaves. Setting plants on a tray of moistened gravel or running a humidifier will help.

Variegated caladiums (at top) can be stored as tubers.                                       Proven Winners

Variegated caladiums (at top) can be stored as tubers.                                       Proven Winners

Insect pests like white flies and spider mites can quickly spread among plants in an indoor collection. Some experts recommend a spray of insecticidal soap, but you can also use a light horticultural oil like Sunspray, which deprives insects of oxygen. While bugs can develop resistance to commonly used pesticides there is no immunity to suffocation.

Overgrown houseplants may need trimming to fit into their allotted spot. If indoor growing space is limited, new plants can easily be made from cuttings – another way to preserve favorite plants through the winter. Coleus, wax and cane varieties of begonias, fuchsias, scented geraniums and silver-leafed plectranthus lend themselves to this technique. Cutting-grown plants are young and more vigorous than fully mature specimens that may have become woody-stemmed and pot bound.

This propagation technique is as simple as taking a healthy new shoot, tucking it into a soilless potting mix (usually peat and Perlite) and keeping the mix moist until roots form. Professional growers often use cubes of Oasis – not the familiar green foam used in the florist trade, but rooting cubes sold for this purpose. (Some online sources: Garden Supply Guys and FloraHydroponics.)

Tropical hibiscus and banana plants can be carried over in a cool spot like an unused bedroom with heat vents closed. Water sparingly and don’t fertilize – the idea is to keep the plant alive, not to stimulate unsustainable growth. Don’t worry if leaves are paler and flowers fail to form.

Tender plants that grow from bulbs or tubers can be stored in a dormant state. These include cannas, calla lilies, caladiums, elephant ears, gladiolus, tuberous begonias and dahlias. Wait until frost has killed the top growth. Then dig up the bulbous underground masses, pack them in sawdust, peat moss or foam peanuts and store them in a frost-free place like a basement or attached garage.

Often your stock will have multiplied over the summer or acquired a heft that means you’ll have a bigger, more spectacular plant next year. Given the cost of some exotic plants, saving them is a matter of dollars and sense.

Gardening is all about thinking ahead. If you can keep some favorite plants going, you won’t be starting from scratch come spring.