Key Points
Houseplants growing under bright light or grow lights benefit from winter fertilization.Skip fertilizing when plant growth stops, as a buildup of unused nutrients can damage roots.Follow fertilizer labels carefully and let visible new growth guide frequency of feeding.
Tweaking your houseplant care regime in winter makes sense. Growth slows (or stops) when there’s less light, lower temperatures, and drier air. However, it’s not just watering and plant position that need adjusting. Your plant’s nutritional needs can also change during this season.
If you’re wondering if you should fertilize houseplants in winter, we’ve got you covered. We asked an expert why a seasonal feeding pause is often recommended for your indoor jungle and when there are exceptions that mean a boost of nutrients can still be beneficial.
Meet the Expert
Justin Hancock is the Director of Research and Development at Costa Farms.
Why Winter Changes Fertilization Frequency
“In winter, when the days are shorter, and the sun is generally less intense, most people find their houseplants’ growth rate slows dramatically,” Justin Hancock, Director of Research and Development at Costa Farms, explains.
This is because plants require light to carry out the essential process of photosynthesis, which involves chlorophyll absorbing light to produce energy (sugars) for growth.
The slowing of growth means that your plant’s water and nutrient demands also decrease, making it easy to overwater and over-fertilize during this period.
When to Fertilize in Winter
According to Hancock, whether you fertilize in winter depends on the amount of light your plants are receiving during winter.
“Light powers growth, and fertilization helps sustain that growth,” Hancock says. “So ultimately, for me, light is the biggest factor—the more light, the more helpful it is to fertilize. The less light your plants receive, the less they’ll benefit from it.”
Below are examples of when plants may actively grow in winter. In these cases, fertilization can help support ongoing healthy root, stem, and leaf development. However, if the growth is slower than in the summer, consider reducing the amount and frequency of fertilization.
When Using Grow Lights
“If you have grow lights, you can fertilize at the same strength and frequency you do in spring and summer because your plants are getting an even amount of light all year long,” Hancock advises.
Consistent use of grow lights for enough hours each day overrides seasonal changes. However, sporadic light supplementation means that adjusting fertilizer use is sensible if plant growth slows.
When Plants Are in a Bright Window
There are times when scaling back rather than stopping fertilizing houseplants in winter can be beneficial. For example,
Hancock recommends this approach when your plants are positioned directly in a sunny south-facing sill. This doesn’t include plants positioned deeper in your home or on a less-bright north-facing window, unless you’re augmenting natural light with short bursts under grow lights.
When It’s Best to Skip Fertilizing During Winter
If your houseplants aren’t actively growing during the winter months, fertilizing isn’t always beneficial, and it can sometimes be harmful.
“If your plants just aren’t growing, then they may not be utilizing a lot of the nutrients you’re providing,” Hancock says. “I’d lean toward minimal or no fertilizing at all in the winter if you’re not seeing signs of new growth. Instead, I’d wait until March or so when the days get longer, and your plants start to respond.”
Excess fertilizer can result in salt buildup in the soil. This draws moisture from the roots and can lead to fertilizer burn. When your plant does start to grow again, it can affect water uptake, result in unhealthy leggy growth, and, in extreme cases, lead to death.
Smart Winter Houseplant Fertilizing Tips
Still not sure about when and how much to fertilize your houseplants in winter? These expert-approved tips can help keep you right.
Always Read the Label
Because every fertilizer has a different formulation, there’s no universal winter ratio. Whatever product you choose, never exceed label recommendations, and always apply fertilizer to already-moist soil to avoid root burn.
“Every fertilizer has a different application rate/frequency recommendation, so it’s not like I can advise to use a cup per week in summer and half a cup per week in winter or anything like that,” Hancock says. “The instructions on the fertilizer label are the maximum amount you should use. You can always go down from there depending on your preferences—and going down can be in frequency, in strength, or both.”
Let Plant Growth Rate Be Your Guide
If you see signs of new growth, such as new leaf buds, growth emerging from the soil, or stems tilting towards light, this is a good indicator that your houseplant will benefit from winter fertilization.
“Personally, I let my plants’ growth rate help guide me,” Hancock says. “My plants in my south-facing windows get regular fertilizer in winter, but those in my north-facing window might get fertilized only once or twice.”
Watch For Signs of Overfertilization
Common warning signs of overfertilization include browning leaf tips, wilting and a white crust on the soil surface or porous pot edges.
Flushing the soil thoroughly with free-draining water helps remove excess salt buildup, or you can repot in a fresh potting mix.
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