All Aroids Greenhouse Molly/Queen of the Greenhouse Silver Cloud Topics Troubleshooting

Hot Weather & the Greenhouse

I have been learnng so much about growing Aroids in the past year and the most “Trial by Error” event was my first heatwave. Four days above 40deg (Celsius) and the last and most damaging day being a crazy 45deg. That last day was the one that caused the most damage.

With another day above 42deg today, I thought I would write about what I have found important for getting my plants through days like this.

My greenhouse has the standard green plastic film found on most cheap, kit form greenhouses. I got it as a solution for keeping my plants in, until I was ready to build a more permanent one. I also have a top cover of 60% shadecloth that covers the East side, roof and front of the set up as it is hit by strong sun until mid afternoon. The inner plastic door is rolled up but still covered with shade cloth. So it has good ventilation and on a standard day. The humidity stays around 50 – 70%. Below 40 deg, it runs well as it is. But…

This picture below is an example of what happened during that first heatwave that gave my botanical butt a good kicking. I hadn’t considered if such a hot day would need extra care and protection.

I hadn’t been able to get out and mist. I just watered the night before, as I do with other plants, expecting that was enough. Now I am determined to never let it happen again. The Philodendron Silver Cloud, I had only had for two weeks. Lucky there was a new leaf that only had a small burn on its side. But it was a massive setback and a bit devastating for my first expensive aroid purchase. Complete rookie mistake! Here is how it looks now… not perfect but much better.

A Begonia that I bought for my Mum for Xmas was also completly fried. Other plants with new leaves were hit hard as well. But I wasn’t the only one that day who got caught. Others were hit harder than me. I guess it’s something we have to deal with now that 45deg days are becoming the norm here in Australia.So, what did I learn? What have I implemented for my own Greenhouse on days above 40deg?

  • Cover your greenhouse with extra shade cloth or old sheets if your set up is small. Especially where the hot sun directly hits. My greenhouse is shaded from 3pm onwards. So I only need to cover the south side, the upper half of the front and the top.
  • Humidity is key. Dry heat is what will damage your plants. You could install a misting system and use a timer on the tap, or use your hose on the finest spray. Mist every few hours to increase the humidity. You could also put pots of Water around the greenhouse to assist in keeping the humidity up. I have a few pots sitting on the ground all the time. I also use them to water a plant that needs it between normal waters and that way they are always filled with fresh water. Molly, my cat also likes drinking out of them.
  • Air flow is also important. Especially when misting, as water sitting on the leaves can damage them. Having a vent or open door can help, it seems to work in my current set up. A fan can also help. I have also been reading about having an evaporative cooling unit to cover airflow, humidity and cooling the space. I have one for my room and it costs only a little more than a fan to run. Alternatively you can get small solar powered fans on Ebay for around $20 that would suit a smaller unit.
    • New and soft leaves will burn easily. Especially if they are sitting up near the roof. Consider sitting them lower or even take them inside where they will be safe from the elements.
    • Keep up and coming weather in mind when potting up plants. The stress of being repotted and the heat could be more than the plant can take. Leave it until after it cools or keep the plant in a cool place to protect it.
  • Water your plants more often. I tend to water daily during heat. My soil is designed to not stay wet so it dosnt become waterlogged if I over water.
  • Feed your plants after a heatwave for a quick “pick me up”. I use a seaweed solution that gives it a good feed. I usually do this once a fortnight anyway, but will give an extra feed to combat stress.
  • Consider the variables of the day in question. If it’s one hot day and the days around it are cooler, you know it won’t be as extreme or heat up by 8am. However if it is day 4 of a heatwave and didn’t get below 35deg all night, then you know it’s a day for pulling all the stops. Over time you work that out. But it only takes one day of not considering the weather to have damaged or dead plants.
  • Yesterday I also learnt the you need to consider the wind as well. I put a sheet on top of my greenhouse for a bit of protection. The wind blew it off as it wasn’t well secured and the plants looked a bit rough at the end of the day from the heat and it becoming dry in there. It’s pointless putting in the effort if your protective layer falls down as soon as you turn around.


So, this is how I combat days over 40deg. In truth, if I am able to I will mist and cover the set up from about 36deg. But anything in the high 30s rings alarm bells for me now.

Having been through another hot day today, it was awesome this evening to see how successfully I managed the greenhouse. By getting conditions right the plants are growing daily and unlike me, they are loving the hot weather. The thrill of new leaves on lots of plants was wonderful. I might do a new post showing the growth from over the past days.

*It is now the next morning and it is 31deg outside at 9.30am. I have been out to mist the plants and was thrilled by the humidity in there. 99% Humidity is not bad!!! The Plants are all happy.

I hope this helps in some way with managing your greenhouse on hot days. Please feel free to share what you do or anything I missed, in the comments below.

Thanks for reading and happy growing. Xx