The short answer is yes, but the reasons might surprise you. PLUS what you feed and how much will probably need to change. You might not be able to see it, but houseplants ARE getting busy over winter, and what they get up is why it matters what you feed over winter.
You should not fertilise the same way in winter as you normally do in warmer months. Depending on your conditions, you might also need to back-off on what you feed and change your focus to match the change in your plant's focus in winter. Plus what you do in winter can save leaf death in spring.
Read on for 'the tea' on the (sometimes controversial), question of whether you should fertilise your indoor plants in winter, so you can make up your mind on what's best for your plants...
#1 Indoor plants don't go dormant
The first thing to know is that most of our indoor plants do not go dormant over winter. Most come from habitats that remain warm, bright and humid all year round, with more consistent temperatures and sunlight levels than we offer them, so are used to growing all year round.
In fact, that's the main reason they make great indoor plants after all! Partly because many grow in low light in jungles and forests, so our 'bright indirect light' indoors is a good match for the low light conditions they grow in outdoors... and partly because we heat our homes in winter. Lucky plants.
Many of our favourites, including Pothos and Alocasia, are native to Southeast Asia, where temperatures average around 27 degrees all year round and sunlight hours barely change regardless of the season, with around 12 hours of sunlight every day, all year.
Many Philodendron varieties are native to Tropical America, a region that includes the Amazon rainforest in Brazil, where the average temperature remains around 25 degrees all year, with 12 hours of sunlight and humidity close to 80% or above even in the 'dry' season.
#2 Indoor plants DON'T need a rest
Some argue plants 'need a rest' in winter and shouldn't be 'forced' to grow all year-round. That certainly is true for plants that die back in winter (like Caladium).
However, most of our tropical indoor plants come from habitats that stay warm all year round, so please don't feel mean! They WANT to grow in winter. You're NOT forcing them to grow. Rainforest plants in the tropics have a 12 month growing season.
What we do need to worry about providing them with in winter, is the warmth, light, nutrients and humidity they love, so they can grow all year round like they want to. And if foliage does slow down or stop growing, don't starve the roots!
Yes, growth will still slow down with cooler temperatures and reduced daylight hours, but most houseplant do NOT go dormant or die back over winter.
#3 Roots don't go dormant
Even when plants appear to go dormant and a plant stops growing above-ground, there is still activity going on under-ground that we can't see.
Roots have their own pattern of growth, which doesn't always follow the same rate of growth as the leaves.
In general, roots tend to show growth spurts in early summer and late autumn to bulk up before winter. But what happens to roots during winter?
Different species and regions have different patterns, however if the soil itself stays above freezing, even outdoor plants that appear dormant above ground, will divert their energy to growing below-ground through winter.
Over winter, plants go into storage mode. Think of them like recharging their batteries. After dealing with high water loss and fuelling fast foliage growth in the warmer months, plants work to both recover and to build up their stores again over winter, ready to power the next rapid growth season when it warms back up and daylight hours increase again.
If starved of what they need over winter, plants can't fully recharge their battery below-ground. It may not make any visible difference above-ground over winter, but come spring and summer, it means you may not see the same foliage growth and flowering you could have.
Not looking after the roots in winter can cause leaf death in spring. Our plants definitely 'play the long game'. The reward for looking after their needs over winter will be seen next growing season.
#4 Nutrient storage increases over winter
As part of 'recharging' their batteries in winter, plants also INCREASE their nutrient storage, conserving energy ready to fuel that first explosive growth next growing season.
Think of it like filling up the fuel tank in winter, ready for putting your foot on the accelerator in summer.
If there's a shortage or deficiency of nutrients in winter, it's not until spring or summer that you notice the effects, which include slow or delayed growth, stunted growth or even yellowing and leaf death, when it should be full steam ahead.
It's easy to blame more immediate actions for growth issues in summer, but in fact it may be what we did (or didn't do), for our plants in winter, that's responsible for setting our plants up for success or failure come spring and summer.
#5 Winter deficiencies cause summer death
One saving grace if you don't fertilise in winter, is that many essential nutrients are mobile. Meaning your plant can move them around itself, such as from old leaves to new leaves.
If you notice a lot of yellowing older leaves during spring and summer, your plant is sending you a message you shouldn't ignore.
Yellowing leaves can be a sign your plant's lacking essential nutrients from the soil. What it can't get from the roots, it's taking from it's older leaves. Essentially sacrificing older leaves by 'sucking' those nutrients out of the older growth, shifting it to keep younger leaves alive and to keep growing.
If you fail to correct what's causing those yellowing leaves, or cut those leaves off, plants will keep sacrificing one leaf after the other until you fix it.
However, not all nutrients are mobile, so for some, once there's a deficiency, your plant can't correct it, and neither can you.
Calcium is a super important one to watch out for. Calcium is essential, but NOT mobile.
Common signs of a calcium deficiency include smaller, slower, stunted or deformed new growth, or new leaves and buds that soon turn brown and die. Yes, that includes premature browning on new variegated growth too.
But by the time you see the impact of a calcium deficiency in new growth, it's too late. Reducing deficiencies (in both mobile and immobile nutrients), is another benefit of fertilising all year round (provided of course that your fertiliser is complete and balanced, and includes calcium!).
If you do see signs of a deficiency from an immobile nutrient like calcium, it may be too late to fix it in that growth, but you CAN correct it so future growth isn't deficient. Better to avoid a deficiency in the first place by fertilising all year round.
How to fertilise in winter
Before I knew the science behind why to fertilise over winter, I did it anyway, simply because I noticed most of my own jungle did slow down, but did not fully stop growing over winter.
Everyone has their own method. Mine is a mix of trial (and error), research and education. Here's what I do for my jungle...
The 'weakly weekly' method
This method is mentioned a lot online, but not always explained. It doesn't literally mean to feed every week. It means you should fertilise less, but more often. So you end up fertilising lightly, every time you water.
This method helps avoid deficiencies while also avoiding fertiliser burn. 'Weak' typically means half to a quarter of what the label says.
For example, if a product says to 'dilute 2 mls per litre, every second water', you might use 1ml per 1 litre, every time you water. I personally decide how much less to feed based on the label, so for a food that recommends monthly use, I'll usually feed about a quarter of that dose. Or for a food that recommends fortnightly or 'every second water' I use half the recommended dose.
And if your fertiliser recommends TINY amounts that are difficult to halve, no worries, double the water instead. For example, instead of 1ml per 1 litre water, do 1ml per 2 litres of water in winter.
Don't ignore the roots!
Even if you decide to skip the fetiliser over winter because nothing at all is going that you can see ABOVE the surface, or your place is simply too cold and dark to support foliage growth in winter; do NOT starve the roots.
In that case, I would stop the fertiliser and switch to support those roots so they can recover and recharge over winter. Here are my top picks below for looking after the roots in winter...
Switch to root support
My top picks for roots in winter...
(and yes, you can use all of these during the growing season also)
GT Rootzone > A root support formula you can use by itself or mix in with your fertiliser of choice to help roots replenish lost nutrients, recover after stress and rebuild, while naturally boosting resistence to common pests and diseases like root rot. This is my #1 pick based on results with my plants.
NurtureSystem No.3 RapidRecovery > This one's new to me so it's still too early to tell you from my own experience but reviews from overseas sound amazing. It's one of world-plant-famous Kaylee Ellen's nutrient range. It's a root growth booster that doubles as rehab and recovery support. Use it by itself in winter or along-side No.1 PowerGrow fertiliser during growing season.
Avoiding fertiliser burn in winter
If you're worried about overdoing it in winter, one thing you can do to reduce the risk is switch to a fertiliser with a lower salt index. It's the salts in fertiliser (and other sources like tap water), than can build up and burn roots and foliage.
GT (Growth Technology), is one fertiliser brand that avoids high salt index ingredients. For GT that means no sodium and no chlorides. They aslo avoid chlorine, nickel and cobalt; phyto-toxins that can burn houseplants.
But rather than throw away otherwise perfectly good fertiliser, you can also reduce the risk of fertiliser burn by both diluting how much you use AND adding an occasional flush water every month or two.
A flush water just means a really thorough water with plain water only, no nutrients. This helps flush out excess mineral salts that have built up over time, whether from fertiliser or just the mineral salts in your water. And yes, an occasional flush water is recommended even if you don't fertilise.
To do a flush, simply top water heavily with plain water, until water really pours out the drainage holes. Then wait about 5 minutes for that to drain out, and repeat.
Flush watering also helps replace stale air with fresh air for the roots. If you normally bottom water, a top water every monh or two is recommended.
How often to water and feed in winter
Back to the 'weakly, weekly' method: In summer that might indeed mean watering weekly, or more often. But as growth slows and temperatures drop, so does your plant's water consumption and evaporation rate.
In winter you would still feed weakly, but not weekly (the grammar nerd in me loves how this makes no sense if you read that aloud).
Depending on the fertiliser you've chosen, you might either feed at quarter to half-strength in winter, every time you water, or use the same dose you did in summer, but water less often in winter.
Remember dose and frequency go together, so simply by watering less often in winter, your plants naturally receive less fertiliser, so you don't have to change the dose. Or you can keep watering at the same frequency if the pant needs it, but change the dilution rate.
Remember, change one or the other. If you were feeding 1ml fertiliser per 1 litre water in summer for example, you could change that to 1ml per 2 litres in winter, but do keep fertilising every time you water.
Stop using growth boosters in winter
If you use a growth booster in summer (like the amazing HB-101 - wow), I personally skip them over winter unless my plants are cheerfully pumping ou new growth at summer rates.
If you give your plants seaweed, then like fertiliser, I would keep giving them seaweed over winter. Seaweed is amazing for roots.
Instead of seaweed, you can 'kill two birds with one stone' (I actually hate that saying), and use GT Rootzone instead. That formula includes marine extracts from seaweed (and much more), to benefits roots, and can be used by itself or mixed with your fertiliser in the same water, so does both.
Or, if your plants do need fertiliser over winter, but you don't want to bother with two bottles to meet their needs, have a look at the all-in-one Plant Runner Indoor Plant Food. That fertiliser combines the essential macro- and micro-nutrients PLUS seaweed in one.
At the end of the day, there's a lot of experimenting in how we care for our plants. I love that about our hobby. I'm always learning. This is what I've learned, and what I do as a result of that learning. But guides like this, after all, are just guides. I hope sharing what I've learned, helps you. And if it does, please feel free to share this with others too :)
Happy growing,
Anna 💚
ABOUT THE AUTHOR: Anna is the owner of plant store Love That Leaf which specialises in products and advice for indoor plants. She is also the resident indoor plants writer for NZ Gardener magazine. Her houseplant care articles appear in print in magazines in-stores NZ-wide, and online on Stuff, The Post, NineHoney and more.