The Top 5 Myths & Mistakes to Avoid Killing Your Indoor Plants

No judgement here. I was once guilty of every single one of these common mistakes myself. That’s one of my favourite things about our hobby. We never stop learning. Find out below the top 5 myths and mistakes to avoid that could be harming your houseplants, causing root rot, stunting their growth and more. I hope this learning helps you, like it helped me and my indoor jungle.

From Anna @lovethatleaf

#1 Don’t add a drainage layer


Is this the exact opposite of what your mum taught you? Me too! Even the name is a myth. It doesn’t increase drainage at all! You’d be better calling it a ‘root rot layer’.


Turns out the tradition of adding a drainage layer – typically bark or pebbles - to the bottom of your pot is super smart, provided that pot’s going outdoors. It sounds like such a good thing, but gravity doesn’t agree.


That layer actually helps retain water, creating what’s called a perched water table, where the water gathers and sits above that layer. That lifts water up closer to the roots. Great for pots outside, where containers dry out too fast. But indoors? That’s the opposite of what you want.


Instead of adding a ‘drainage layer’ DIY or buy your plants a free-draining, indoor potting mix. Add that right to the bottom of the pot. That will keep water free-flowing down and out.


I love the Bioleaf potting mix for my jungle but you can DIY your own using substrates like perlite, orchid bark, charcoal and fern fibre. If you’re worried about losing soil out the drainage holes when you water, just trim some drainage mesh to fit. Job done.

 

#2 Do feed your plants in winter


This is another myth that comes from our outdoor garden buddies. The majority of indoor plants don’t ‘need a rest’ or go dormant in winter like many do outdoors.


In fact, most of our favourite tropical-loving indoor plants come from habitats with a 12 month growing season, where it stays warm and humid all year round. They simply grow faster or slower according to the season, but don’t go dormant.


Subjected to colder temperatures and reduced daylight hours in winter, indoor plants will slow down, but don’t completely stop growing (there are a handful of exceptions like Caladium that die back down to a bulb in winter).


Even when leaf growth slows down or stops, our indoor jungle is busy growing below the surface. Plants shift their energy to their roots over winter. Roots don’t go dormant. In fact, nutrient storage increases over winter.


Think of it like your plant putting itself on charge after running their batteries low powering rapid growth in Spring and Summer. Plants replenish, then increase their nutrient stores in winter, building up nutrients and conserving energy, ready to power the next growing season.


Plants also play the long game. If you starve your plants over winter, most nutrient deficiencies won’t make themselves known right away. Come spring is when those deficiencies can cause smaller, slower growth, or in the case of less mobile nutrients, even deformed new growth, or leaves and buds that soon brown and die early.


Instead, try the ‘weakly weekly’ method. Do feed throughout the year, but less in winter. Bonus content about the ‘weakly weekly’ method coming up at the end.

 

#3 Don’t cut yellow leaves off (and no, yellow leaves are not normal!)

 

Have you even been given the advice to just cut off yellowing leaves? That it’s ‘just an old leaf’? Totally normal and nothing to worry about? I’ve also been told you should cut them off because they ‘use up the plants energy’.


In fact, it’s entirely the other way around! Those yellowing leaves are your plant’s life support system right now. If you do cut them off, without fixing the reason why, your plant will take another leaf, and another, until you either find and fix the cause, or it eventually runs out of life support leaves and dies.

 

Here’s what’s really going on…


Provided it’s not caused by something like disease, yellowing leaves is your plant trying to survive! If there’s an essential nutrient your plant can’t get from the roots like it would normally, it will switch on life support, and take those nutrients from its leaves instead. Our clever plants send those missing nutrients to their newer leaves, so it can keep growing and stay alive.

 

#1. Water


The #1 reason for yellowing of older leaves is water. You’ll likely know if you’ve been overwatering, underwatering, or leaving your plant dry too long between watering. All can cause root damage, and damaged roots can’t absorb the water, or other nutrients along with it, that your plant needs. What it now can’t get from its roots, your plants will take from its leaves instead.

 

#2. Minerals


Another common culprit of yellowing leaves is a mineral deficiency, often nitrogen. Here's what to look for:

 

  • A nitrogen deficiency shows as general yellowing on older leaves first. Nitrogen’s the most common one because it’s avery mobile nutrient. When you water, you wash the nitrogen away, which is why it’s often recommend to fertilise regularly to replace the nitrogen and keep up with your plant’s needs.

  • Potassium deficiency is another, which shows as leaf edges that turn yellow while the inner leaf stays green, often with older leaf edges turning yellow first, then brown on the edges.

 

  • Magnesium deficiency can show as yellow patches between the veins on older leaves first, which yellow from the centre out, with the edges turning yellow last.

 

  • Iron deficiency shows as yellowing between leaf veins also, but on newer leaves

 

  • Sulphur deficiency starts on the newest leaves first also, turning the entire leaves yellow.


If you don’t fertilise, or your fertiliser isn’t complete and balanced, take this as a sign from your plants to look at improving what you feed. More about fertiliser coming up in the bonus section.

 

#4 Don’t use eggshells or milk (but why your plants do need calcium)

 

Unlike nitrogen and other mobile nutrients, calcium is an immobile nutrient. That means when your plant is deficient in calcium, it can’t just take it from another leaf.

Calcium is an essential macronutrient, meaning plants need high levels of calcium. Yet it’s the other macros – nitrogen, phosphorus and potassium – that normally get all the attention. It’s a common mistake to think because you fertilise, you can’t have a calcium deficiency, however if you check the label you’ll find a good 99% of fertilisers do not include calcium.


That’s also why there are lots of ‘hacks’ online for how to increase calcium for indoor plants. Eggshells, milk water, dolomite lime, gypsum, yoghurt, molasses and more. Before we look at how to fix a deficiency, let’s check the signs.

 

Common signs of a calcium deficiency to watch out for

 

  • stunted, smaller leaves
  • weaker stems
  • tip dieback on leaves
  • deformed leaves
  • cracked or split leaves or fruit
  • leaves that ‘cup’ or curl
  • buds that form but die before flowering or fruiting
  • increased disease and insect attack


The bad news is you can’t correct a calcium deficiency in that stem or leaf, as the calcium was required back when it was forming. A deficiency when growing, is a deficiency for the life of that stem or leaf. The good news is you can correct it for the future, so it doesn’t harm new growth.


Milk water
, yoghurt and molasses can end up smelling and attracting fungus gnats as they rot and break down (unless you water it down so much that it doesn’t provide enough calcium).


Dolomite lime
is an excellent way to quickly increase calcium, but can also change the soil pH (which can be a good or a bad thing). Take care to follow the directions. If you can, test your soil pH before and after. Dolomite lime needs reapplying every 3 months / once a season. Here’s how to apply dolomite lime and how much to use for indoor plants.


Eggshells
are quite honestly a waste of time. In a compost heap outside they have been shown to take years to break down. And that’s in ideal conditions! For our indoor plants, even with drying out and smashing the shells down into a fine powder, they may not break down at all. If they do, your plants may not benefit for a very long time.

 

The solution is easier than it seems


My own method when rehabbing a plant is to start with a single application of dolomite lime for an instant boost (I use the Yates Dolomite Lime), then continue with a complete and balanced fertiliser. Sounds simple - and yes, you can skip the dolomite lime step - but you’d be surprised how few fertilisers actually include calcium!


If your fertiliser doesn’t include calcium, sprinkle on a little dolomite lime once a season. Do a soil pH test too. You want to aim for a pH of 6. You can also consider the change to a fertiliser that does provide calcium. See if you can find out the ‘ppm’ (that’s parts per million) for how much calcium the fertiliser provides once diluted.


For example, the one I use for my jungle is around 100ppm. There are a handful on the market that include calcium, like GT Foliage Focus and Dyna-Gro Foliage Pro.


If you’ve added calcium but are still seeing signs of a deficiency, there might be something blocking your plant getting the calcium you’re giving it. Just dumping more calcium on isn’t going to help if this essential nutrient can’t get to where it needs to be.


Calcium travels around your plant with water, so you want to avoid underwatering. A soil pH around 6 is best both for calcium absorption and all the major nutrients, so best to raise or lower your soil pH first if needed or that extra calcium will go to waste.


Cold temperatures
also reduce calcium uptake. Consider a heat pad over winter if your place gets below about 15 degrees on the regular. Although many of our favourite tropical indoor plants prefer high humidity, that needs to come with good airflow, otherwise the combo of high humidity and stagnant air can also reduce calcium getting where it’s needed. VPD (Vapor Pressure Deficit) is a fascinating subject to read up more about balancing heat, humidity and airflow for ideal nutrient and water uptake and increased growth.

 

#5 Plants don't like being rootbound


I’ve heard ‘plants like being rootbound’ said so often that it feels like it has to be a fact, right? Not at all! Of course plants don’t like being rootbound. Plants outdoors don't have compact little root balls only growing directly underneath them. So why do we do this to them indoors? To save plants from us!


Kept in ‘too big’ a pot the chance of root rot goes WAY up. Lots more substrate means lots more capacity to hold water. Root rot can be a death-sentence. A smaller pot reduces the chances of root rot, protecting plants from over-watering. Under-watering and less substrate is so much safer. Water again too soon, or keep the substrate too moist, and that smaller pot could be a life saver.


Another benefit (for us) is forced reproduction. In response to the stress of being rootbound, plants can divert their energy from growing roots and leaves to survival mode. For some that means flowers, for other’s pups. Flowers make US happy and it’s easy to think flowers mean a happy plant, but they might be super stressed and responding to conditions that tell them they’re going to die.


Limiting space for roots limits growth
. Want a bigger plant? Don’t be scared to pot up. BUT - and this is biggie - be extra careful about what you pot into.


The bigger the pot, the more important a free-draining, airy substrate becomes. Typical indoor potting mix holds too much moisture for too long, drowning roots. Buy or DIY a substrate that holds little to no water to make a larger pot safer. I love the Bioleaf potting mix.


You’ll often see advice to pot up 1 to 2 sizes only. For example, from a 14cm wide pot to a 16cm wide pot. Another benefit of not potting up too big is leaf growth. When you jump up too much in pot size, a plant can appear to ‘stop growing’. That’s normal. And it is still growing, but not where you can see it.


Once they recover from repotting, plants given much more room than before will shift growth to below-ground instead. They get busy sending roots out to explore all that new space first, instead of growing leaves. If you do upsize too big too soon, you may have a long time to wait before your plants diverts its energy from the roots back to stems and leaves.


Two other considerations are looks and space. With a jungle my size, huge pots restrict how many plants I can fit. See? All about me again ;) Plus I admit some plants look plain silly in a pot that’s ‘too big’.

 

Bonus: The ‘weakly weekly’ fertiliser method


This method gets talked about a lot but is rarely explained. Although it’s simple once you know what it means, I guess more experienced indoor plant hobbyists are so used to it they forget we were all beginners once.


This method does not literally mean to fertilise every week. It means to feed lightly, every time you water. This helps to avoid deficiencies (especially in immobile nutrients like calcium), while also avoiding excess building up and causing issues like toxic soil pH and fertiliser burn.


As for how much to reduce the dose by, my own rule of thumb is to halve or quarter what the fertiliser label says, depending on the frequency it recommends.


If a fertiliser recommends using it once a month, I quarter the dose and use it every time I water. If it says to use every second water, I halve it every time I water. For a brand that already gives you the dose based on using it every time you water, there’s no need to change anything.

 

How much fertiliser should you use in winter?


Back to mistake #2 for a moment. Since we know plant growth slows down over winter, you will likely need to reduce how much you feed over winter (note that’s reduce, not stop!).


If you’ve noticed growth has slowed down, keep fertilising ‘weakly weekly’ but reduce the dose to match the reduced growth. For me I simply double the water, which effectively halves the dose.


For example, if you use 1ml fertiliser per 1 litre water during peak growing season, when growth slows down, change that to 1mls fertiliser per 2 litreswater instead. You could of course also change it to 0.5mls per 1 litre water if you prefer – and have a tiny pipette to measure it with - so either halve the fertiliser and keep the water the same, or double the water and keep the fertiliser amount the same.


Some of my plants are in a prop tank (I have one of those Exo Terra terrariums). They grow happily all year round. In winter I turn on their grow light (I use one of the Grow Bar kits), and turn on the heat pad underneath (I like the Cultiv8 heat mats). For those plants I keep their fertiliser at ‘summer levels’ all year round.

 

Tips for avoiding fertiliser burn


Some ingredients in fertilisers come with an increased risk of fertiliser burn. Urea is a common one. Urea is an excellent source of readily-available nitrogen, and nitrogen is essential for plants. Not such a concern for outdoor plants, as excess urea can leach away from sensitive roots. However our indoor plants aren’t so lucky. Their roots can’t escape. There are fertilisers on the market now that are free of urea to help reduce the risk. Finding a urea-free fertiliser isn't easy. If you’re really worried about burning delicate plants, also look for a fertiliser that’s uses a chloride-free source of potassium.


I’m not saying you should bin your fertiliser if it does have urea or chlorides in it! Remember most fertilisers do. The good news is there's another very easy way to reduce the risk of fertiliser burn, no matter what fertiliser you use.


Simply top water until water really pours out the drainage holes. This helps flush out excess mineral salts such as urea. Even if you prefer to bottom water, swap for one good top water flush about once a month to stop those mineral salts building up over time and burning roots and leaves or changing soil pH.


The fertiliser I currently use is both urea-free and chloride-free, is formulated for the ‘weakly weekly’ method to be used every time you water, is pH buffered to 6, includes calcium, and is complete and balanced. I add in a light seaweed feed about once a month also (for seaweed I use the Biopower organic seaweed flakes).


However I also used to use a superb fertiliser my plants loved, that happens to include urea (remember most do), and didn’t include calcium (again, most fertilisers don’t), and wasn’t chloride-free (most aren't). It did include seaweed, the ‘super-food’ for plants. I used to top water, and also sprinkled a little dolomite lime in each plant once a season for calcium.


It just goes to show – similar to nutrition for people - that there most certainly is not only one food, or one way, or even a ‘right way’ to look after our plants. Experiences and opinions differ almost as much as the needs of our plants are different. Luckily thanks to the range of products we have readily available these days, there are lots of different ways to meet your plant’s needs.

 

Well there I go again. In my usual fashion I’ve gone a written a short novel! I do hope you learned something new. I love sharing what I’ve learned, including admitting to the mistakes I’ve made, and the myths I also used to believe in!

If you want to continue your learning, there are more free plant care guides waiting for you on my blog, and lots of plant care tips on my Instagram too :)


Anna @lovethatleaf