Green roof challenges & advice

I had sedums at my old house, took a while, like three years maybe four, for it to establish properly then it was fine 

New house I'm going to try for strawberries on the shed roof

I would work with nature, not against it. If clover likes it, and then longer roots won't damage things, then I would plant more varieties of clover and leave it be.

Maybe try some other varieties of sedum. I put a huge range into ours and some has absolutely thrived and others disappeared. I pick up bits of sedum all over. Often find bits in old walls, garage roofing, pavement cracks. Take a bit and leave enough for the plant to survive and spread and you can harvest more later. Now the preferred varieties have taken over it takes very little maintenance and looks super healthy.

Ours is 10 years old this year and we've had a few people comment that it seems particularly happy (it's looking a little more sparse right now as autumn hits, and we had some fox digging issues this summer).

We do put some effort into weeding it a few times a year, and taking out as much grass as we can.  I think some moss is natural and don't see that as an issue. it gets an appropriate amount of slow release sedum fertiliser each spring. If it's really dry for an extended period I might stick the sprinkler on it once to give it a bit of a boost (I did this year).  We built ours up from components- matting, plastic water retention tray, big bags of sedum soil base, sedum turf over the top. There were meant to be something like a dozen different species.  Whether there ever were is debatable but there seem to about 4 now. 

Next door's was supposed to be 'wild flowers'.  It's grass and weeds - they grow big and green for a few weeks in spring, then spend the summer looking parched and dead until they die back.  I've surreptitiously planted excess sedum that's been growing in our pebble surround over the years which is spreading over more and more of it which looks good when the grass dies back.

installed as a series of mats

What do you mean?  Preplanted plastic tray 'modules'? and how much of a slope? the advice I got is that while those are quicker (and thus cheaper) to install, they never work as well.  I'd also wonder about the degree of slope as I'd expect that to affect how much water retained. 

The fox gave us the biggest issues we've had so far as it repeatedly dug up quite a large area.  Bird have never done a lot of damage - we seem to have a good population of tiny snails and they come in for those at some point in the year.  more of an issue is them shitting on the parapet wall rather than pulling up the sedum.  Bee's love it when it's in flower. 

Thanks everyone for the input, appreciate it! I feel slightly less doom and gloom about it all now! I'm still not sure of the clover - once it takes root it really does choke everything else out, so it's a clover-or-other things choice. 

Posted by: b33k34

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What do you mean?  Preplanted plastic tray 'modules'? and how much of a slope? the advice I got is that while those are quicker (and thus cheaper) to install, they never work as well.  I'd also wonder about the degree of slope as I'd expect that to affect how much water retained. 

Huh, interesting point. Yeah, it was modules - it's 90sqm or so, so doing it by hand, as part of the construction, was never going to work well. The slope for most of the roof is maybe 15degrees or so, and it has occurred to me this summer that that means the water never really sticks around; particularly with the soil being so thin, it's all run off within an hour or two. But again, I figure the moss, while not desirable, helps keep some of the moisture around. 

Posted by: nicko74

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Thanks everyone for the input, appreciate it! I feel slightly less doom and gloom about it all now! I'm still not sure of the clover - once it takes root it really does choke everything else out, so it's a clover-or-other things choice. 

Posted by: b33k34

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What do you mean?  Preplanted plastic tray 'modules'? and how much of a slope? the advice I got is that while those are quicker (and thus cheaper) to install, they never work as well.  I'd also wonder about the degree of slope as I'd expect that to affect how much water retained. 

Huh, interesting point. Yeah, it was modules - it's 90sqm or so, so doing it by hand, as part of the construction, was never going to work well. The slope for most of the roof is maybe 15degrees or so, and it has occurred to me this summer that that means the water never really sticks around; particularly with the soil being so thin, it's all run off within an hour or two. But again, I figure the moss, while not desirable, helps keep some of the moisture around. 

 

90m2 !! I think ours is c16.... and looking back at the orders we were told to aim for a minimum of 60mm soil substrate with the 'turf' on top but I think we went some way beyond that (we needed more than one dumpy bag so had loads) 

More than 60mm of soil plus the mats sounds like a lot. I made a weak soil mix, equal parts soil, crushed clay tiles and perlite. Maybe 30mm deep with the sedum planted directly in it. I think sedum is pretty happy to grow in a very wide range of substrates though so whatever works.

Posted by: nickjb

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More than 60mm of soil plus the mats sounds like a lot. I made a weak soil mix, equal parts soil, crushed clay tiles and perlite. Maybe 30mm deep with the sedum planted directly in it. I think sedum is pretty happy to grow in a very wide range of substrates though so whatever works.

Lindum sedum substrate.  a mix of topsoil (and mostly) clay balls back then.