The principle of a GreenRoofTops sedum roof is that it should be as maintenance free as possible. That said, no green roof will be totally maintenance free.
Sedum is an unusual plant in that it will grow where other plants do not do well and this is the environment we need to create on the roof. Most importantly there should be just the right amount of substrate for the plants to grow in. This will allow the sedum to flourish, but not enough for weeds and other invaders to become established. The substrate should provide enough nutrition and water holding capacity for the sedum, but not for weeds.
Don’t be tempted to water it every time it looks a bit dry but leave it to its own devices unless you have maybe reached that sixth week without rain which is unusual in this country. If you cannot water it at all, do not worry as sedum is one of the most drought resistant plants and it will out-live pretty much anything else on the roof so don't panic! In fact we hear of more problems caused by watering and over fertilizing resulting in lush growth and consequent die back than from drought.
Sedum naturally lives in rock crevices on cliffs and other exposed situations where growing conditions are naturally harsh so it needs to be "lean and mean" on the roof. We need to ensure that nutrition is kept to the minimum that it requires so the plants are given enough to survive and flourish but not enough to allow lavish growth. Ideally take a photo of your roof every now and then so you can see any trends occurring.
We recommend to apply OSMOCOTE slow release fertilizer every 6 or 12 month in April or October, depending on how your roof is looking.
Weeds: From time to time it is likely that weeds may get established on your roof. They can arrive as seeds on the wind or by birds and it is perfectly normal. The best policy is to tackle it before it gets to be a problem. The best way to remove them is simply by pulling. It is more likely that weeds can become established if the sedum growth is poor and you have bare patches - this will be caused by lack of nutrition for the sedum
If you do have bare patches then it is time to give the whole roof a good dose of fertilizer, then from the good areas, pull off a few cuttings and sprinkle them on the thin areas, then put some compost on top to slightly cover but not completely bury the cuttings. This will anchor them down and help rooting. Do this in the autumn or spring and they will root very readily.
As sedum is slow growing it may appear that nothing is changing, however if you take a photo every now and then, you have something to compare. Then if in doubt send us a couple of pics and we will advise.