Spring and autumn are my favourite seasons for myself, but for my plants, summer takes first place. Plenty of light, long daylight hours, warmth and higher humidity (here in New Zealand anyway!).
All that new growth is an absolute joy. Cuttings can't wait to grow roots. New leaves everywhere I look. It's a houseplant hobbyists dream.
But there are some heartbreaking mistakes that can happen in summer that can quickly turn that dream into a nightmare for us and our plants.
Luckily, once you know what to watch out for, you can prevent these common mistakes and protect your houseplants this summer. Here's what's on my summer prep to do list...
#1 Under-watering kills fast in summer
Did you already guess #1 on the list? No, not the usual generic warning about over-watering (although yes, of course that still applies all year round). But come summer, it's under-watering that gets really risky.
Summer conditions can mean a plant dries out super fast. A plant that didn't need watering just a few days ago may be literally dying of thirst tomorrow.
For an under-waterer like me, I have to be extra careful my plants don't turn into crispy husks in summer. Especially my moisture lovers like my many peace lilies and prayer plants.
Make sure when you do water in summer, to always water heavily, so ALL the potting mix gets fully saturated and no roots miss out.
Watering heavily does NOT cause over-watering or root rot
It's watering again too soon that you need to watch out for, as well as the wrong potting mix that holds too much water or stays wet too long, without enough air to match your plant's needs.
It's a common misconception that root rot is only caused by over-watering. Under-watering can cause root rot too and it's more likely to happen to your plants in summer.
If you water too lightly, or not often enough, some roots may miss out, dry out and die. Next time you water, those dead roots rot. And in summer, it can happen fast.
PS: If you've ever had a plant die of root rot but you know for sure you did not over-water, now you know why.
#2 Picking the right potting mix saves (plant) lives
If you still have repotting left on your spring to do list, do it now.
Picking the right potting mix could be a life-saver in summer, but not in the way you might think.
One summer saver is to shift your moisture lovers into a more water-retentive substrate.
Look for one that stays moist for longer and has good wicking ability to keep the mix evenly moist throughout, helping avoid those dry pockets that kill roots and risk root rot.
I LOVE the Bio Leaf Potting Mix for Moisture Lovers. I have my peace lilies, African violets, calathea, maranta, stromanthe, spider plants, flowering anthurium, aglaonema, begonias and more in that mix.
Honestly an absolute life-saver in summer for many of my plants.
But if you're prone to over-watering, or you have plants that HATE wet feet, a chunky, airy potting mix could be the life saver your plants have on their wish-list.
Mixes like the Rare Plantation Chunky Aroid Blend and best-selling Bio Leaf Aroid Medium Potting Mix help protect from root rot by maintaining pockets of life-saving oxygen, even right away when freshly watered.
I have my monstera, pothos, hoya, epipremnum, scindapsus and more in those chunky, faster-draining, lower water-retentive mixes.
And for your semi-succulents, succulents and cacti (fun fact: all cacti are succulents), mine are loving the newer Bio Leaf Succulent and Bio Leaf Cacti mixes.
#3 When water kills
If you're like me, along with 70% of other houseplant hobbyists, tap water is your go-to water source.
And no, I'm NOT about to tell you off and suggest you only use rain water.
But the reason tap water is called the silent summer killer becomes way more obvious this time of year. Plants go through water faster and you're having to water again much more often.
That means your water source has a bigger impact on your plant's health in summer than any other time of year.
That's also why it might look like using tap water is completely fine, until suddenly it isn't.
For most houseplants, chlorine in tap water is tolerated. It won't burn roots or scorch and kill leaves right away. It's sneaky. Taking its time. Slowly building up long before you see the signs.
But for all houseplants, chlorine can be BAD news. For some sooner than others.
You may be shocked to hear most fertilisers include chlorine and it's buddy chlorides.
But hold your horses. Plants do need some chlorine. But we're talking TINY amounts. There's little risk of a deficiency but a big risk of too much.
When you consider there's chlorine and chlorides naturally occuring in organic potting mixes, AND in most fertilisers, AND even in the air (especially in coastal regions), as WELL as in your tap water; it's no surprise EXCESS chlorine, and NOT a chlorine defiency, is the bigger worry for houseplants.
That's a lot of words in all caps there (and a painfully long sentence sorry), but you can see why it quickly adds up.
If you can remove, or at least reduce, those multiple sources of chlorine, your plants will thank you for it this summer, especially the long list of more chlorine-sensitive houseplants.
Experts might argue that includes ALL houseplants, but the more chlorine-sensitive ones I'd worry about are peace lilies, African violets, aglaonema, begonias, calathea, maranta, stromanthe, orchids, spider plants, dracaena, carnivorous plants, ferns and palms.
One thing you can do to help protect your plants from this summer risk is to simply treat your tap water with Water Drops from Phytology.
That product instantly removes chlorine AND you can use it in the same water as your fertiliser.
(most chlorine removing products are NOT plant friendly - they are made for fish tanks not houseplants - because they also strip essential minerals from your fertiliser, risking nutrient deficiencies)
Another thing you can do is pick a fertiliser that's free of chlorine, chlorides, sodium and other high-risk ingredients.
Like any of the GT Focus range like the best-seller GT Foliage Focus, but there's also GT Orchid Focus, GT Flower Focus, GT Succulent Focus... if you see Focus in the name you know you're safe.
#4 Watch out, pests are coming
Spring and summer are the season pests can appear in abundance, seemingly out of nowhere.
🪳 Spider Mites love the heat.
🪳 Fungus Gnats love late spring and early summer in particular,
(but of course our indoor conditions keep them pretty happy all year round)
🪳 Mealybugs and Scale ramp up reproduction in spring and summer,
🪳 Aphids and mealybugs target tender new spring and summer growth to feed on,
🪳 Thrips peak substantially in spring and summer and munch on new growth too.
That's a long list that gives me the creepy crawlies just reading it.
Now is the time of year for a little close inspection, especially underneath leaves where the vampire pests like to hang out and feed on your plant's lifeblood (sap), hidden from prying eyes.
If you find something suspicious, snap a photo and DM me on Facebook or Instagram, or share it in the free Houseplant Help group on Facebook for a second opinion just in case.
This time of year you might like to start preventive treatments too.
Most treatments that are safe to use as a preventative are shorter-acting contact insecticides that you can use more often.
The big guns - like a systemic (Groventive is one example) - CANNOT be used too often, or you risk creating resistant super-bugs.
Some safer preventative options include:
For fungus gnats, a few drops of Tanlin in the water makes quick work of any maggots in the pot, getting ready to turn into those annoying flying adults.
Add Tanlin every time you water (and yes, you CAN add it in to the same water with your Water Drops to remove chlorine, and your fertiliser).
For soft-bodied nasties, like aphids and spider mites, a regular spray with gentle insecticidal soap like Yates Natrasoap or certified organic Enspray 99 mineral oil works a treat.
Enspray 99 also works on harder-bodied pests like mealybugs, scale and thrips. Bonus is it's a broad fungicide too.
Just make sure to get good coverage including spraying that hiding spot underneath leaves too (I use one of those 360 misters which spray upside-down).
(always follow the advice for dose, directions, precautions etc on the label and listed on those linked product pages)
#5 Spring cleaning for summer
No, not for the aesthestics or the 'gram. A quick clean at the start of spring and again heading into summer could be life-saving...
Clean leaves saves lives
Spider mites LOVE it warm and dusty but pest prevention is not the only reason to keep leaves clean.
A regular leaf clean with Plant Runner Neem Spray or Forsana Foliage Magic gets rid of dust and dirt.
Enspray 99 can be used as a leaf spray also with the added bonus of killing pests and being a fungicide.
Dust-free, dirt-free. Prettier for us, better for photosynthesis, and less appealing for pests. Everyone wins.
Feed everyone
Even fertiliser-sensitive houseplants need a good feed during growing season.
If you skipped fertilising them over autumn and winter, start feeding in spring to avoid a long list of common spring and summer issues.
If you didn't start in spring, start right now!
The right fertiliser will help increase leaf growth, support buds and blooms, reduce premature browning, reduce yellowing and much more.
Need a hand picking the best fertiliser?
This guide explains the 4 plant food levels and which food matches your plants needs best >
More air, less plant killers
Next up is a little plant shuffle and snip, as well as fixing your sinking plants.
And yes, just opening your windows helps too, but it's more than that.
Increase space between your plants, and if all that new growth is too dense, a little snip or dividing helps increase airflow between stems too.
Powdery mildew is one common killer that loves warmth, humidity and low airflow.
If you have plants who are slowly sinking, but you don't want to repot them, slide them out and just add fresh soil underneath them instead.
Plants sink down in their pots over time as soil ages and becomes more compact, reducing airflow and increasing the risk of root rot, powdery mildew and other fungal diseases.
Find out more about treating and preventing powdery mildew here >
Avoiding the scorch
Speaking of doing the plant shuffle, summer is also the time to check your plants are in a safe spot for the season.
Check the path of the sun in case it's shifted and could now burn your plants during the day.
Also check your direct sun lovers aren't cooking. I shift mine where they get morning or later afternoon sun, avoiding the intense midday sun in summer.
Also watch out for shifts in temperature. Instead of worrying about cold drops in winter, watch out for spikes in temperatures that can scorch leaves, even out of the path of direct sun.
I also would avoid watering and leaving or putting indoor plants outside in summer - and definitely avoid a little sunbathing outdoors - as the summer sun is far more intense outdoors and can quickly burn your indoor plants, even if left in the shade outside.
5 easy to avoid mistakes that could save a plant life this summer. I hope these help you protect your plants this season.
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.