The faithful readers amongs you will know that we have two Sedum grass roofs on our house; An intensive roof on the house (that is with serious structure, soil and ‘real’ grass and plants) and an extensive roof (that is with less structure & sedum ‘grass’) over the shed.
I gave an update on the roofs this January HERE and things were looking good and the sedum roof did flower. But the roof never returned to it’s original ‘greeness’. Since that time the roof began to look sorrier and sorrier; the amount of sun that we got dried it out and then it was hit with deluges of rain. The roof started to shrink around the edges and maintained it’s redness throughout; frankly I was worried.
I tried to find some guidelines for caring for the sedum to no avail and hence this blog post. If you’re interested in the science I did however find THIS DOCUMENT later on the ‘Comparison of Organic and Synthetic Fertilizers for Sedum Green Roof Maintenance’
• You need to care for your Sedum.
I mistakenly thought that I rolled the Sedum out and then left it without lifting a finger. Big error; a sedum roof needs to be maintained & looked after. And in our instance when the roof was shrinking and staying red it was in distress and needed feeding.
To do this we used a fertiliser. You can get specialist sedum fertilisers (example HERE) but we opted for a granular fertiliser; Ideally I read that the the NPK proportions (Nitrogen, Phosphorus, Potassium) should be equal but in the end we went for one to promote ‘greenness’ rather than growth. From memort I think it was 18:6:12). The granules were then spread over the roof the evening before rain was forecast – this is to ensure the phosphorus doesn’t burn the sedums.
And what a difference a little bit of TLC made. here’s the roof before any fertiliser (looking very red):
And below is a slideshow and close-ups of the roof flowering and going green (at last). This fertliser is going to be applied Spring and Summer.:
Note: The small white patches are the granules of fertiliser. Eventually the water will dissolve these into the growing medium
Next post is on our Intensive roof and getting rid of moss!