Are your houseplants suffering from dried leaf tips or leaves that roll under? Or that turn yellow and fall off prematurely? Or flower buds that dry up without opening? If is, it’s likely that the air in your home is too dry, a major problem in most homes, especially in late fall and winter.
To check this out, install an electronic thermometer/hygrometer (humidity reader) near your plants: they are easy to find in any hardware store. If the humidity level shown is less than 50%, and it probably will be, it’s insufficient for most plants.
You can help your plants get back in shape by using a “humidity tray”. Bonsai and orchid nurseries often sell commercial ones, but it’s easier and much cheaper to make your own using readily available materials.
First find a “tray” larger than the plant’s pot… ideally one large enough for several plants. This could be a plant tray, a large saucer, a muffin container, a baking dish, the bottom of a Tupperware container, a kitty litter tray or pretty much any container that is large, fairly shallow, impermeable and rust-resistant.
Fill the tray with gravel, pebbles, expanded clay pellets, glass marbles, marble chips, etc. and spread them equally to form a flat surface. Some gardeners like to use plastic egg crate (the panels used to direct light from fluorescent lamps) cut to size for this purpose. Then pour water into the tray so that the substrate or the panelis covered in water to three-quarters of its height, but without flooding it completely.
You’ve just created an environment from which moisture will rise up onto the substrate by capillary action, then evaporate into the surrounding air, increasing the atmospheric humidity very locally. Next place your plants directly on the tray (you won’t need a plant saucer) and they’ll benefit from their own personal humidifier.
From now on, every time you water let a bit of extra water flow into the humidity tray. That way there’ll always be water evaporating upwards and your plants will benefit from higher humidity 24 hours a day.
Humidity trays are especially useful during the months when you heat your home, because heating the air dries it out. You can continue to use the humidity tray all year if you want to (it’s never harmful), but in most climates, the air indoors is naturally more humid in the summer and a humidity tray won’t be as useful… unless you use an air conditioner, because cooling the air dries it too. In that case, it is better to use your humidity tray year round.