What we grow as house plants are tropical plants in other areas of the world where the weather is warm enough for them to grow outside all year. Since we are forcing these plants to adapt to our dry heat in the winter and unnatural air conditioning in the summer, many of these plants actually appreciate being moved outside for the summer where temperature and humidity more closely mimic their native places of origin. The trick is getting them acclimated gradually to the more intense outside light.
Plants may be moved outside after May 15 which is considered the last date for frost in our area. Most tropical plants can tolerate a brief drop in temperature to about 45°, but if frost settles on the leaves, the foliage may be irreparably damaged. Gradually acclimate sun-loving plants to a full sun (6 or more hours) location by moving the plants to an area that gets either bright indirect light or just a few hours of early morning sun. After a week or so, move the plants to a sunnier location where they will receive 4-5 hours of morning sun. After another week, plants may be moved to their full sun location. This process allows the plants to gradually adjust to higher light levels without damaging the foliage. Plants that prefer shade can usually be put in the desired location without any adjustment.
Repot plants at this time, if necessary. Use a professional potting soil that is lightweight and drains well. Consider adding water retention crystals to the potting mix especially for those plants in sunny locations. These crystals absorb many times their weight in water, releasing it as necessary, thus lengthening the interval between waterings. Because longer day lengths trigger more active plant growth, fertilize plants regularly from April through September. Slow release fertilizers such as Osmocote may be used as well as water- soluble fertilizers such as Jack’s Classic. Follow package directions for correct application.
The end of September is a good time to start bringing plants in for the winter. A more gradual adjustment to inside conditions means less stress on the plant. In any case, plants must be brought inside before the first frost. Begin by checking your plants for any signs of insects before you bring them inside. If you’re an attentive gardener, you’ll have been doing this right along! Treat with the appropriate remedy at least a week before bringing indoors and then check again just to make sure all is well. Flushing the soil thoroughly 3 to 4 times the day before bringing indoors will help to remove any insects that may have crawled into the drainage holes. Replacing the top 1-2” of soil will remove eggs of fungus gnats — little black ‘fruit-fly’ type of insects.
If you can, place plants where they will receive light conditions similar to what they received outdoors. Keep plants away from air vents. If your house is very dry, a humidifier will make things more comfortable for plants, pets and you! Tucking a pot of water behind furniture or between plants will help to increase humidity in that area. Grouping plants together also helps maintain a more humid atmosphere around the plants. Water needs generally decrease during the winter months as foliar growth is greatly reduced. If the plant is near a heat source, pay close attention to its water needs. Fertilizing is usually not required October through March. If fertilizing is needed, half strength solutions are best.
When you bring blooming plants such as hibiscus, mandevilla, passion vine, plumbago, etc. indoors, they will usually have both flowers and buds. Given enough light, the buds should continue to open until around Thanksgiving. Anytime before April 1 is a good time to trim and shape your blooming tropicals. The amount of pruning depends on how large you want them to grow next summer.
Don’t be alarmed if your tropicals start dropping yellow leaves during the winter. This is a natural response to lower light levels, less humidity and a plant’s inclination to shed older foliage. Yellow, shedding leaves should be more from the center of the plant and not at the tips. This mimics the shedding that pines, hollies and other evergreens do during the fall and winter.
With a little care, you can have luscious tropicals that will beautify both your outdoor and indoor living spaces and will continue to grow and provide many years of enjoyment!