Everyone wants thriving and happy houseplants. Fertilizing is an important component for healthy plants yet house temperatures and the amount of light a plant receives will influence how fast or slow a plant grows. Unlike outdoor plants that are more influenced by the weather and may tend to go dormant in cold temperatures, houseplants don’t typically stop growing entirely. They do have their growth cycle, often slowing down in the winter when plants typically receive less light. In winter, days are shorter and have lower light levels. “Since light is the fuel for plant growth, most plants see significantly less growth during the winter months,” says Justin Hancock, a horticulturist for Costa Farms, one of the largest horticultural growers in the world, headquartered in Florida. Plants that are growing at a slower rate likely won’t need fertilizer. Yet there are nuances to know to determine if reducing how often you fertilize is a good idea.
Houseplants Don’t Go Dormant
Houseplants typically have times when growth slows down based on lower light levels, but they don’t stop growing entirely. “The truth is most of your typical houseplants are not going dormant in the winter (northern hemisphere),” says Leslie F. Halleck, certified professional horticulturist and author of Gardening Under Lights, in Dallas, Texas. There can be confusion as the slowed-down growth is commonly referred to as dormancy, explains Hancock.
“Most houseplants—tropicals, bulbs, succulents/cacti—may experience what we call seasonal quiescence, rather than true dormancy,” says Halleck. “Quiescence simply means a slowing or quieting of growth, but it doesn’t stop altogether.”
Dormancy occurs when specific factors are provoked. “True dormancy is a biological process triggered by genetics and environmental stimuli that results in the cessation of ALL cell division and growth,” explains Halleck. “That means no leaf or root growth at all until certain environmental conditions are met and plant genes restart the clock, after which growth can resume.”
There isn’t a one-size-fits-all answer when it comes to houseplants and fertilizer. Although it may be colder outside and there is less daylight, your home is likely warm with the thermostat set at a cozy temperature, and more lights may be turned on. This ould provide an environment that permits your houseplants to continue growing at their typical growth rate instead of slowing down in the winter.
Why Plants Need Fertilizer
Fertilizer provides plants with a nutrient boost that helps them grow. “Fertilizing houseplants is helpful to keep them happy and growing,” explains Hancock. “The more you fertilize, as long as it’s not in excess, the more and faster they’ll grow,” he says. Plants that don’t receive fertilizer will grow but typically at a slower rate, even during the more active growing period. According to Hancock, “Most houseplants will survive (note: survive, not thrive) without fertilizer, especially if you repot every year or two.”
“If your plants aren’t getting enough light and fertilizer during this time, you may lose your blooms or plants may not bloom as well,” says Halleck. However, a houseplant that receives less light, will need less water and may not need to be fertilized. “If you have a Pothos ivy that is getting much less natural light and you are watering it less, then you’d want to skip the fertilizer in winter or dilute it down to 1/4th the strength if you want to keep feeding it,” explains Halleck.
How Much to Fertilize Houseplants
“As a general rule, most typical tropical and succulent houseplants are light feeders,” says Halleck. “You don’t really don’t need to fertilize them a lot to keep them happy.” So how often should you fertilize houseplants? “Most common houseplants do well with a quarterly seasonal application of fertilizer,” she says. There are some exceptions as some high-light plants and flowering plants, including orchids or African violets, need extra nutrients to produce flowers and do best with weekly or monthly fertilizer, Halleck explains.
Do I Need to Fertilize in the Winter?
The more light a plant receives, the more it will grow. Because there is typically less natural light in winter due to shorter days and often gray, gloomy skies, houseplants will grow slower. Lower light levels and cooler temperatures mean plants will photosynthesize slower and absorb water and nutrients more slowly, says Halleck. According to Deborah Landau, Director of Ecological Management for The Nature Conservancy for Maryland and Washington, D.C., “Slower growth means they’re not using as much energy, so don’t need or cannot utilize the extra nutrients.” When houseplants are growing at a slower rate, according to Hancock, “additional nutrients aren’t really necessary for the plant.” Fertilizing in winter comes down to knowing your houseplants and their needs.
Hancock fertilizes houseplants when they are growing quickly, not when they are in a slower growth mode. “I recommend fertilizing while [houseplants are] in active growth mode so they’ll use most of the nutrients you’re giving them and using a general-purpose product labeled for use on houseplants,” he says. Hancock points out that there is a possibility of nutrient salts building up in the soil when fertilizing in winter since you usually need to water less frequently. Halleck shares a similar sentiment: “If your plant is actively growing in winter and you want to encourage it to keep doing so, or your plant appears nutrient deficient, then go ahead and fertilize it,” she says. “It just comes down to what your plant actually needs.”
If you prefer fertilizing year-round, Landau suggests diluting the mix to ½ to ¼ strength in the winter. “If you are watering less often in the winter, and you usually fertilize when you water, then the plants are already getting less fertilizer, so keep that in mind when calculating how much to dilute,” explains Landau.
Can You Over-Fertilize Your Houseplants?
Fertilizing your houseplants year-round without adjusting the amount could have negative consequences for your indoor plants. “If you’re fertilizing your plant with the same quantity or on the same frequency you were during a more active growing cycle, then you can have excess fertilizer build up at the root zone,” says Halleck, “which can be toxic to your plant and actually make it harder for your plant’s roots to absorb water and nutrients.”
