One Question Quiz
Image: Archi Banal
Image: Archi Banal

SocietyNovember 25, 2023

Their house, my garden: How to deal with sick plants

Image: Archi Banal
Image: Archi Banal

This week on Their house, my garden, we get a nasty surprise. Despite all our love and attention, one certain green member of the cucurbitaceae family has a rotten end.

There are mornings when you feel young and sprightly and accomplished because you’ve just emptied out the compost before you’ve even had a sip of caffeine. Sadly these mornings can all too easily be ruined by a quick check of the garden. 

Just days ago we added our first two zucchinis to a Spanish omelette, and they were so tender and so sweet. But alas, now the plant is sporting a deformed zucchini with a brown spot on its end. The bloody thing’s come down with blossom end rot. 

Gardening is great because once you’ve figured out how to solve one problem, like slugs and snails, a new problem will present itself. New experiences are good for us and our brain plasticity, I’m told. In the past I have only known zucchini plants to be diligent in producing beautiful big yellow flowers (edible) and also so many zucchini you have to get very creative, very generous and even use your freezer. They’ve been so well behaved I got sick of them. So forgive me for lingering on this hideous brown spot.

It isn’t my first sickly child. Below is a list of ailments that my plants and my friends’ plants have suffered, and so I am assuming are widespread. If you haven’t spied disease in your garden, there are tips for prevention, which is better than any cure.

Blossom end rot

Gross! Blossom end rot on zucchini and tomatoes.

Blossom end rot is currently maiming my zucchini, but can also strike tomatoes, capsicum and eggplants. It’s caused by a lack of calcium, but, embarrassingly for a gardening columnist, it happens when you mess up the most basic of gardening tasks – watering.

When watering is inconsistent, it is difficult for the plant to take up calcium from the soil and carry it all the way to the ends of the fruit. The circulation of the plant is compromised and so the extremities suffer, like when you get cold fingers and toes.

The solution, then, is to be better. If it’s not raining you should be watering at least every second day, and I don’t mean a light sprinkle of drops, it should be a drenching. Someone once told me each tomato plant should get 10 seconds of full hose stream, and I reckon the same applies to other plants. The garden bed should be mulched to help with water retention. If an inspector were to come and poke their finger into your soil, it should be moist at all times.

That being said, tomatoes are extremely hungry for calcium, and it pays to top up the amounts of it in the soil around them. Some free ways to do this are to always rinse and empty your milk bottles at their bases, and to collect up your eggshells, grind them into a powder, and sprinkle them around the tomatoes. You can also buy calcium fertilisers if you’re flash and don’t mind spending money (or are vegan). 

Wrinkly drop-off

Are your vegetables kind of forming and then simply withering away prematurely? It seems this can happen to any fruiting plant – for me it’s been pumpkins and zucchini (perhaps they’re not so well-behaved after all). This ailment has been given the lovely name of fruit abortion, but I suggest we change it to wrinkly drop-off.

Wrinkly drop-off is caused by the flowers not being pollinated properly. You can pollinate them yourself as a short-term emergency solution but I would also plant some flowers in order to attract more pollinators to your garden. 

You need only a little paintbrush to pollinate flowers by hand, and to be able to determine which flowers are male and which are female. Basically, you dab pollen from the male flowers onto the bits of the female flowers. The best guide I’ve found is this video which begins with a love triangle.


Gardeners freak out about blight. I think it is because it gets in the soil, and then could contaminate your tomatoes for the rest of time or until you move out. The recommendation with blight is to pull your tomatoes out ASAP and destroy them. I do not know if people actually do this. It seems pretty harsh.

There are two blights, early and late. Both are types of fungus. Early blight likes warm and humid conditions and late blight likes wet and cold conditions, so they’ve got it all covered.

Blight also likes a lack of ventilation, so some breeze is good for tomatoes. You might want to trim a few leaves off to allow for airflow if you have planted your tomatoes close together.

Blight is why we try not to wet our tomato plants when we water them. You will spot blight because dark spots will show up on your tomato plants either on the stem or on leaves. Yellow will spread from the dark spots on the leaves. If you catch it early, I would let your plant live. First remove any affected leaves and put them in the rubbish bin, not the compost bin. I hope that in the landfill, blight will die.

Do not think you can ignore blight – your tomatoes will be black and rotten. It is gross and you won’t want to eat them. There are plenty of fungicides for blight (it’s probably a lucrative market) but you can also make your own from stuff in your kitchen.

DIY fungicide 

  • 1 teaspoon baking soda
  • 4 cups water
  • a drop of dish detergent
  • 1 tablespoon vegetable oil

Put everything into a spray bottle (ideally reusing an old one) and shake. You will probably have to shake before each application. Spray on the whole plant and any any nearby tomato plants in the early evening.

Reapply every few days, and keep an eye on the blight. If it gets worse, abandon and destroy.

Powdery mildew 

Early and advanced powdery mildew on a zucchini leaf.

I have never not had a little bit of powdery mildew on my zucchini leaves. It looks the way it sounds, powdery and white. It also grows on cucumber and pumpkin leaves. It’s nothing to worry about until it spreads, but spread it will. 

Some things you could do to control it are cutting off affected leaves, and spraying with our DIY fungicide. Some people on the internet have said that dousing plants in milk gets rid of it too, but people on the internet say all kinds of things that I cannot confirm are true.


Not technically a sickness but definitely not good. If the aphids are being farmed by ants, I personally would leave them alone because ants are very hardworking and deserve that sweet sweet honeydew. If there isn’t a battalion of ants around them, and they’re all up in your plants, I’d worry. They multiply quickly when it’s warm so before you know it whole plants are covered in the tiny green bugs. 

It’s important to deal with them as soon as you see them. Apparently if you blast them off your plants with the hose a few times a day they will be discouraged and leave. If this doesn’t work you can also apply soapy (not too soapy) water, which they also don’t like. 

Way too many aphids on a cabbage plant, and way too many mealy bugs on a spinach leaf.

Mealy bug

These bugs are trying to be cute with plenty of white fluff, but actually they are creepy. Why are their legs so long, and their back scales so gross? They’re kind of like aphids in that they make honeydew and ants like them, and should be dealt with in a similar way. They can be pretty hard to kill because they hide. 

Root rot

If all the leaves on your plants start turning brown and dying for no reason you can see, it’s possible they have root rot. It’s a pathogen in the soil that causes roots to rot, and so plants die (sad). Plants are susceptible to it when they have been overwatered, as basically their roots are sitting in water all the time. I think our feet would also rot if we did this. Basically you can under-water and over-water and knowing the sweet spot in between can be one of life’s great mysteries, or checked by poking your finger deep in your soil. It should feel like a wet sponge… but not sopping wet. How wet is a wet sponge is perhaps another of life’s great mysteries. 

If it’s too late for that, first cut off the bits of your plant that are dying (they can’t come back to life sorry). Then, we need to kill the pathogen in the soil. Mix half a tablespoon of bleach into a bucket of water, and drench the soil around sick plants. Like antibiotics and your gut, this is going to kill all the tiny good stuff too, but it’s worth it because not many worse things could happen than your plant’s roots rotting. 

It’s never too late to appreciate a flower or save your plant from blossom end rot.

Plant illnesses are usually not death sentences. The best way to ward off sickness in any plant is to keep them healthy, so that any baddies attacking them can’t do too much damage because they can fight back. Another couple of days after the sad discovery of the blossom rot, I was charmed by two large yellow flowers on the zucchini plant. Underneath them, a large and perfectly formed zucchini was waiting for me.

Tip of the week: Keep a close eye on your plants so you can spot sickness before it progresses too far.

Tasks: Get better at watering.

Keep going!