If you had taken your houseplants outside for the summer, now is the time to bring them back indoors. The forecast for the weekend has low temperatures just below 50F. While this brief dip may not be fatal to the tropical plants we enjoy as houseplants, they don't tolerate these temperatures for very long.
Your houseplants may need some extra help to adjust to being brought back indoors. After all, you have now drastically altered their growing conditions. Most important is light, as the leaves of plants are basically solar panels. Even your biggest and sunniest windowsill might not offer as much light as the shade outdoors. Don't believe me? Download a light meter app to your phone and compare. Clean your windows first to let the maximum amount of light in.
By far, the best information I've found about the light requirements for common houseplants comes from the University of Missouri, as they discuss measuring light intensity in foot candles. Again, this is why you downloaded that light meter app. Typically, houseplants are categorized as "high light," "medium light," or "low light." The trouble is, human eyes are pretty bad at judging light intensity. Sure, we squint when blinded by light that's too bright and our eyes adjust to night vision after a few minutes in the dark, but it's really hard to judge anything else that occurs anywhere in between. Besides, light intensity varies by latitude, time of day, and time of year. "Low light" can mean something entirely different to gardeners in Florida or Southern California than it does for us in Washington, DC.
Bringing it back home, the reality is that most of us live in homes that are darker than our plants would prefer. If you find that you need to supplement your indoor light conditions, install some grow lights. While not marketed by the manufacturer as growlights, FEIT's 4-foot LED shop lights were recommended during my master gardener training because they're inexpensive, LEDs use less energy than fluorescent bulbs (thereby saving you on your electricity bill), they're long-lasting, and spectral analysis of this specific product shows sufficient coverage in the 400nm to 700nm range that plants need for healthy growth. There are other growlight options available to you, this is just one of them, so choose what works best for you.
Other important considerations besides light are humidity and watering. Our home environments are definitely drier than humid DC summers. To supplement the humidity, you can mist your plants with a spray bottle, but I find that to be messy. I prefer to use pebble trays: set the pots on top of saucers or trays filled with pebbles and pour a little water into the tray. The pebbles will keep the pots out of direct contact with water so that you don't overwater your plants. You may need to refill the water in the pebble tray more often than you'll need to actually water your plants; don't water your plants just to refill the pebble tray with the drained excess water or you might overwater your plants. As the water evaporates from the tray, it will increase the humidity around your plants. Having your plants clustered near one another will also help to maintain the humidity of the immediate area.
Of course, indoor potted plants require less frequent watering than potted plants outdoors, so adjust your watering habits accordingly. The frequency with which you will need to water your plants depends on the type of plant, the size of the plant, the size of the pot, the amount of light they receive, temperature, and humidity. Since the angle of sunlight is lower in the winter, plants slow their metabolic processes in response, so less water is needed at this time of year than for plants kept indoors throughout the summer. Likewise, houseplants need little to no fertilizer in the winter.
One more thing before bringing in your houseplants. Thoroughly check your plants for unwanted stowaways and leave the bugs outside where they belong. Scrub dirt and debris from your pots with a dry brush. Scan the leaves, stems, fruits, and flowers, removing eggs or cocoons. A gentle spray with the hose will dislodge aphids. If you must use chemical sprays to treat an infestation, insecticidal soaps and oils are the least harmful options.
Making full use of my South-facing double windows, from left to right: 'David Bowie' dragon fruit, 'Lake Atitlan Red' dragon fruit (I've nicknamed it "Michael Jackson" to have two pop stars in the garden, as the red fruit made me think of Thriller), key limequat, plumeria, dwarf banana, and Meyer lemon. Behind the dragon fruit cuttings and obscured from view in this photo, I've also got blue agave and aloe vera. There are pebble trays beneath the citrus and there are no growlights at this time. Clearly I'm going to have to come up with a new plan for next year, as some of these will need repotting in the spring and they'll all be bigger by next fall.