Written by Jan Eastman | Chair PRHRiA
Perth Summers are always a trial for those who love growing roses and year 2023 ended and 2024 started with severe heatwaves which severely affects the growth and flowering habit of the roses. We have endured many days in the high 30’s and into the 40’s. How do we care for our garden in this sort of extreme weather?
Firstly, we need to prepare the garden ahead of Summer so that your roses are conditioned to stand these sort of conditions.
MulchÂ
Mulching your garden to hold the water that you give it is a very important way of preparing your garden. Mulch stops those very hot sun rays from scorching the soil, burning the roots and drying out the water you have given it. I always mulch in Spring but there are areas that require a top up before the sun warms right up. I use Lupin Mulch but you may have a preference and it doesn’t really matter just as long as it is keeping the moisture in.
Water
Everything loves a drink of water, even yourself and it is absolutely necessary during these hot dry days. Watering late in the evening usually gives the plants the best benefit as the moisture lasts longer during the evening giving the plants a cooler time to take up the moisture. Give them a good spray overhead as the leaves also take up the moisture and refreshes the plants. Some people may query watering a rose in the evening worrying about giving them blackspot etc but no damage is done during summer as the moisture that would do the damage has well and truly dried out before this can take place.
Tonic
During this heat the plants need some extra care and I spray them with Seasol from time to time and this gives them a good boost. Seasol is a natural product, it promotes heathy roots, encourages beneficial soil micro-organisms, stimulates flowering and fruiting and helps plants to cope with stresses like heat, drought, frost and pest and disease attack. I find the plants respond to a good spray of this.
NO Pruning
The roses are best left as they are during hot periods, I don’t even dead head too often. Don’t make the plant work hard as it is under enough stress as it is.
NO Fertiliser
During this very hot weather I do not fertilise the roses. This puts more stress on the rose as it then wants to push out new growth and this will only get burnt in the sun and encourages the Thrip as they only attack the new growth.
Pests
Chilli Thrip is the biggest pest during these hot summer months and it simply goes mad on the plants that are stressed. There are many different theories or ideas on how to control the pest.  Some say that overhead spraying of water works well, but the thrips are most prevalent during the hottest part of the day when you are not to have your reticulation on and I am not about to stand out in the heat and spray my roses, and they dry far too quickly and if you have a large number of roses this is just not feasible. Â
Below: Tea Rose Safrano with Chilli Thrip
There are a number of different products for sale that help with the control but even with that you must be rigid with the timing from the first spray to the next, and if you are a few days out then the Thrip will have already started to take over again. Â
You cannot spray if the heat is going to be above 28 and you cannot spray if there is a wind. Do not spray when the bees are active as the wet spray affects them when it gets on their wings and they will go back to the hive and die and the hive will die also.  Some sprays that are available are Yates Ultra Success and a new one I’ve used is Richgro’s Beat A Bug which has Chilli and Garlic in it and many use on their vegetables too. I have found so far this is working well when I am able to spray.  There are also granular products and one is Richgro‘s Bug Killa however I do not use it on roses that are in flower and I only use these on Spring flowering only roses after they have flowered and during Winter.  Always read the instructions and speak with other friends to see what works well for them.
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Do not cut off the effected stems of your roses, let them flower even though will more than likely be deformed and then just dead head. The more you cut back the less likely the plant is going to recover because the Thrip only attacks the new growth.
Roses that Cope in the Heat
In my garden most of the old roses cope in the very hot weather except Gallicas struggle and do not always make it through the season. Damask roses in my garden do very well and I guess as they originated from the Middle East they are more customed to these conditions. The old Tea roses do well along with the Chinas, Hybrid Musks and many others. This is the first year I have ever seen some of the leaves look as though I had taken a blow torch to them as they burnt so badly in the couple of days of 43 degree heat but the leaves will come back again and new growth is already starting to appear.
Old roses are worth every bit of your attention as they will repay you with amazing perfumed blooms. Enjoy your time in the garden.