Some annuals can move inside for the winter
Cooler temperatures signal the time for us to decide which plants will be awarded a trip inside to spend winter as houseplants and which will be sentenced to the compost bin.
Some of the candidates we grow as annuals to consider overwintering indoors include bedding types and Dragon Wing begonias, coleus, cordyline, euphorbia, fiber optic grass, geraniums, mandevilla, phormium and succulents.
To prepare them for a new environment with lower light conditions, move them to a shady spot in the garden for a week or so before the big move.
Inspect them for signs of insect pests. It's a lot easier to deal with them outside than inside. Check all parts of the plant including the stems and undersides of leaves — favorite hiding spots. Spray plants with a garden hose to rid them of any stowaways. Spray with neem oil if necessary.
Insects can also hitch a ride in the soil. Serve them an eviction notice by drenching them — except succulents or other plants that require dry soil — with water. Dunk smaller pots in a bucket of water. Clean pots, including the bottoms where spiders leave eggs, before bringing them inside.
Dragon Wing and bedding-type begonias need a spot with bright light but not direct sun. Keep the soil slightly moist and continue to feed with half-strength fertilizer.
Overwinter coleus in pots or take cuttings. If repotting, trim back foliage by half to reduce stress. Water thoroughly and keep the soil slightly moist in a location with bright, indirect light. To take cuttings, cut 3 to 4 inches from the tips of stems, remove the bottom leaves, and root them in moist potting mix or in a glass of water. After they have grown roots, transplant them into small pots.
Cordyline overwinters easily in bright, indirect light. Water thoroughly and then let the soil dry completely before watering again. Mist the plant daily to provide humidity or place it on a saucer of pebbles filled with water. Do not fertilize cordyline in the winter.
The euphorbia Ascot Rainbow and fiber optic grass are a couple of my favorite foliage plants. They overwinter in a sunny, south-facing window in my kitchen. While they favor the same light conditions, the euphorbia prefers its soil to dry out between waterings and the fiber optic grass is happiest in moist soil.
Repot geraniums, cut their foliage and roots back by half and put them in a sunny window to spend the winter. Let the soil dry between waterings and withhold fertilizer. The plants may lose a few leaves and get leggy but when you prune them in spring, they will quickly rebound.
Another way to save geraniums is to take cuttings. Cut 3 to 4 inch pieces from soft, green stems. Remove leaves from the bottom half of the stems, dip them into rooting hormone, and stick them into a pot of vermiculite. Wrap the pot with a plastic bag to create a humid environment. After the cuttings root in 6 to 8 weeks, plant them and move pots to a cool, sunny spot.
Mandevilla vines are quite content sitting in a sunny spot with high humidity. Notorious for spider mites, inspect them carefully before bringing them inside. Let the soil dry between waterings and continue to fertilize at half-strength throughout the winter. Mandevilla vines may even flower indoors.
Even though phormium doesn't bloom, it will perform nicely as a houseplant in a sunny window with lots of humidity. There is no need to fertilize.
Succulents are easy to overwinter in a sunny location. They don't require much water and don't want any fertilizer.
Deciding which plants get those precious spots in sunny windows may be the most difficult part of overwintering annuals as houseplants. Don't crowd them together — it is better to sacrifice a few plants than impede good air circulation.
• Diana Stoll is a horticulturist, garden writer and the garden center manager at The Planter's Palette in Winfield. She blogs at gardenwithdiana.com.