When days begin to shorten and temperatures drop, plants go into protection mode. Most houseplants slow down their growth and some go into real dormancy. Why are they doing this, and as plant parents, how can we help?
Dead or Dormant? How to Tell
If your houseplants begin to look sad, how can you tell if they’re dying or if they’re just slowing down or going dormant? Dormant and resting plants will droop, their leaves will sometimes turn yellow and drop, and they won’t put on any new growth.
If you’re still not sure, you can try the scratch and snap test. Scratch a little off the surface of a mature stem, and if it’s green inside, it’s still alive. You can also snap a twig or stem, and if it’s dry and snaps easily, the plant is dead. If it’s flexible and hard to break, it’s a good bet that your plant is alive, but is taking a winter snooze.
Another way to tell is to look at the roots. If the roots are black, or slimy, rotten, and smelly, your plant has died. But if they’re healthy and look as they normally do, the plant is alive and is just resting.
What is winter slowdown or houseplant dormancy?
Winter slowdown or houseplant dormancy are the protection programs that plants go into to survive less than optimal conditions for their growth in the winter. Their growth slows down and they may drop some leaves, and then they don’t actively grow again until spring.
Real dormancy is when plants essentially stop growing. They lose their leaves, need darkened conditions, and no, or almost no, water. Most houseplants don’t go through a real dormancy, they just rest to conserve their energy and protect what they have. Read on as we address both.
Why do they slow down or go dormant?
Most houseplants are from the tropics, and under the favorable conditions where they come from, like steady sunlight, warmth, and lots of water and humidity, they grow year round. Tropical plants will only go dormant to protect themselves in times of stress like with fire or drought.
But when they’re grown as houseplants in temperate regions, they encounter shorter days and lower light in the winter months, lower humidity, and uneven temperatures. They just need to slow their growth to accommodate these conditions — they don’t photosynthesize as much, and therefore they don’t need as much water.
Other plants, such as those with bulbs, corms, rhizomes, or tubers, actually go dormant in the winter, and some even in the summer, like Cyclamen. They need a period of complete rest in the dark. When grown as houseplants, they need to be handled differently than those that are just slowing down.
Image Credit: Brina Blum - Unsplash
What can we do to help our plants through winter slowdown?
Plant parents look on winter as a bleak time for their houseplants. The plants often look kind of sad, they may drop some leaves, and they don’t grow much. It’s important to understand each of the plants’ needs to keep them healthy during this time, which is approximately September through February.
Don’t water as much
The general recommendation for watering most houseplants during the growing season is when the soil is dry 1” to 2” down from the top, or once every 7 to 10 days. During the winter when the plants slow down, though, you’ll need to slow down the watering too. Water them when the soil is almost dry, or once every 21 to 30 days, depending on the heat in the house. If the heat dries the soil sooner than every three to four weeks, water them at that time. Allowing them to dry out too much will just add to their stress.
Boost the humidity
The air in a heated house can become pretty dry in the winter for both people and their plants. Plants are happiest with 50% to 60% humidity that is generally found in unheated houses during the spring and summer. During the winter, the humidity in heated houses can be as low as 30% to 40%, especially around heaters and heating vents, which is not optimal for houseplants.
If the humidity in your house is too low due to the heating, there are ways to increase it for your plants. Use a humidifier if you have one, or set your plants on a pebble tray with water. Just be sure the bottom of the pots are above the water line so they don’t absorb any water. You can mist them, too, on a regular basis. Since plants exhale water vapor, grouping them together increases the humidity around them as well.
During the plants’ resting period, they are in a holding mode. They don’t need fertilizer or extra nutrients since they aren’t actively growing.
Clean the leaves
Houseplants that are resting need plenty of light as opposed to plants that are actually dormant. It’s important to keep their leaves clean so they can catch all of the available rays.
Check for pests
Any pests that bother your plants will stress them out even more during their rest period. Check them over to make sure they are pest free. If you find any unwanted visitors, wash them off if you can, then wipe the plant’s leaves and stems with neem oil to keep them from coming back.
Keep them away from drafts and cold windows
Houseplants in general don’t respond well to drafts — it can be as detrimental as overwatering. Pull them back a little from cold, drafty windows, or relocate them to a bright, warm location that’s protected from drafts. Plants should be in temperatures that are 65⁰ to 75⁰ F during the day, and no colder than 50⁰ F at night.
Keep them in the light or keep them in the dark?
Houseplants that are just resting will need plenty of light to be healthy. BUT, houseplants that are actually going dormant will need to be moved to darkened areas. How can you tell the difference? NOTE: You have to know your plants.
Here are some familiar houseplants that need to rest at one point during the year:
• Aloe vera (Aloe barbadensis) - slows down in summer
• Asparagus fern (Asparagus aethiopicus)
• Bromeliads (Vreisea sp., Guzmania sp., Neoregelia sp., Billbergia sp., Tillandsia sp., Aechmea sp., Ananas sp.)
• Cacti and succulents - some slow down in the summer and some in the winter
• Corn plant (Dracaena fragrans)
• English Ivy (Hedera helix)
• Pothos, Devil’s ivy (Epipremnum aureum)
• Fiddle-leaf fig (Ficus lyrata)
• Flaming Katy (Kalanchoe blossfeldiana) - slows down in the summer
• Jade plant (Crassula ovata) - slows down in the summer
• Monstera (Monstera deliciosa, Monstera adansonii)
• Money tree (Pachira aquatic)
• Philodendron (Philodendron sp.)
• Radiator plant (Peperomia sp.) - slows in summer; grows most in autumn and spring
• Snake plant (Dracaena trifasciata, syn. Sansevieria trifasciata)
• Spider plant (Chlorophytum comosum)
• String of Hearts (Ceropegia woodii)
• String of Dolphins (Dendrophorbium peregrinus, syn. Senecio peregrinus)
• String of Pearls (Curio rowleyanus, syn. Senecio rowleyanus)
• ZZ plant (Zamioculcas zamiifolia)
What can we do to help our plants through dormancy?
Most plants with bulbs, rhizomes, corms, or tubers will go fully dormant in the winter, and some will go dormant in the summer. The way to handle dormancy in these plants is to stop all fertilizing, and reduce watering until the tops die back and the soil is dry.
Remove the bulbs, rhizomes, corms, or tubers from the soil and let them dry out for one to two weeks. Then place them in a paper bag with some dry peat and store them in a cool, dark place until March (September for summer dormant plants), when you can replant them, water them, and watch them come alive.
Here are some familiar plants that truly go dormant:
• Aglaonema (Aglaonema sp.)
• Alocasia (Alocasia sp.)
• Elephant Ear, Caladium (Caladium sp.)
• Calathea (Calathea sp.)
• Cyclamen (Cyclamen sp.) - summer dormant
• False Shamrock, Oxalis (Oxalis sp.)
• Gloxinia (Sinningia speciosa)
• Tuberous Begonia (Begonia × tuberhybrida)
Winter slowdown or dormancy is tough for both plants and plant parents. Hang in there, though, and give your plants what they need over this time period. Your plants will thank you and come alive, and be beautiful again in the spring.