If you are caring for a sedum roof, you will probably notice its appearance will change from one season to the next. Dry weather can trigger a change in plants, and you may not be aware of how to deal with them in the right way. Here’s what to expect and how to care for your sedum roof in hot dry weather.
Sedum plants are incredibly drought-tolerant, but not completely drought-proof. The UK has enjoyed many heat waves in the last few years. So, it’s inevitable that green roofs and sedum mats will start to react and change their appearance because of the hot dry weather, but is there anything you can do about it? In this article, we will take a look at sedum roof maintenance during hot dry periods, including dealing with heat stress and drought stress.
This sedum roof has an array of problems. The plants you can see are quite healthy, however, coverage is sparse. The cause? inadequate feeding and lack of irrigation when it was installed.
Recognising Signs of Heat Stress on a Sedum Roof
Sedums are part of the plant family known as Crassulaceae. They are cousins to the pineapple, aloe vera and Sempervivums. These plants are all characterised by thick fleshy leaves which act as water storage vessels. They also have a waxy coating on the outside of the leaf to help prevent evaporation and have adapted their metabolism to minimise water loss. Compared to many herbaceous plants commonly grown in the UK, they are remarkably resilient to drought.
Whilst lettuces, geraniums and potato plants are wilting in the heat, sedums deploy their unique anti-drought mechanism where chemical processes within the plant are altered. Without being too scientific, suffice to say that you will see a difference in the plants. The leaves turn change from large, plump and green to becoming smaller, red and turgid.
So when your sedum roof changes from green to red, there is nothing to worry about. The plants are coping with the weather in their own way. If, however, the leaves on your plants on your sedum mat start to become pale or ashen-looking and take on the texture of a deflated balloon, this means the plants are struggling to cope with drought and they need emergency assistance.
Does Your Sedum Roof Need to Be Irrigated in Hot Weather?
The whole principle behind sedum roofs is that they are low-maintenance and virtually self-sustaining. Apart from an annual feed and an occasional weeding, they should look after themselves.
Sedums are remarkably resilient little plants and ideally suited to low-maintenance green roofing. However, in extreme conditions, they may need a little extra TLC.
If your sedum roof turns red, but the leaves are still glossy and turgid, there’s no need to water it. The changes are cosmetic and temporary, but please keep an eye out for any further changes.
The brilliant thing about the sedum’s survival mode is that it lives while the plants you don’t want will fade away. Hot dry weather will kill off the weeds so you don’t have to, so look upon this time as a free maintenance session. Unless of course, the plants you do want are suffering.
When sedum leaves look like wrinkled balloons, you should start to take action by irrigating them.
Treating Sedum Roof Drought Stress with Irrigation
At TurfOnline, we always advise watering a stressed sedum roof only when absolutely necessary.
If you need to irrigate, do it by watering the roof thoroughly to the point of runoff. Water in the evening as the sun is beginning to set – that way less of the precious resource will be lost to evaporation.
Repeat this every day for at least a week, because it can take a while for them to rehydrate since the green roof substrate (growing medium) contains only a small percentage of organic material.
At the end of the first week, apply a green roof feed to help boost the plants’ recovery. Water it in, then reduce the frequency of watering to just twice a week until the drought ends.
Related Information
Find out what to expect from your green roof maintenance in summer here.
Sedum Species 
Sedum roof construction 
