Succulent

rickyburtonsmith86

Hello all, 

I am currently working on a green top pergola, and was thinking of putting succulents on there, I'm after information on varieties that are Hardy. 
They will need to be able to stay out over winter, the postion of the pergola will get constant direct sun. 
I live in Essex snow and frost is a possibility but not in overwhelm amounts. 
Also information on substrate..
I have around 50mm of substrate depth is this enough for small succulents? 

wild edges

How much of the roof bit will you see? IE do you need trailing plants or taller plants so they can actually be seen or will mat forming plants do the job just as well?

I like to mix things up a bit. Most sedums that you can find in garden centres will do well on a green roof but some are deciduous and look bare over the winter. Sempervivums can be a good choice but need more maintenance than you think as they die off after flowering and it's better to remove the dead material if you can. Certain saxifrages make great green roof plants and are really underrated. They make nice big rosettes though and tall flower spikes which can break up the look of smaller leaved sedums.

wild edges

An example of a good saxifrage to the left in the pic below. It'll need a bit more soil depth than true succulents but they're bomb-proof otherwise. I've got some sat in the greenhouse at the moment that have been bare-root since last year and they're still alive waiting to be potted up.

rickyburtonsmith86

Thank you wild edges,

Saxifrage is new to me I will have a read up on them, low laying succulents would probably not be seen, unless planted towards the edge of the roof, I didn't even consider trailing succulents.

From your information maybe I will put trailing and Sempervivums towards the edge of the roof for maintaining and viewing.
Then scatter saxifrage towards the centre. 

wild edges

Sedum album trails well as does sedum rupestre. Rupestre comes in a whole range of colours from blue through to gold so it's well worth getting a few to mix and match. You might be able to get cuttings of both for free if you ask on freecycle as they're very common plants. I'd get some sedum spurium too as the flowers are very vivid.

You can use small rocks and logs to make areas of deeper soil like mini raised beds which allows you to try other alpine plants too.

KeenOnGreen

We've lost most of our Saxifrages, possibly not enough drainage in Winter, so they wouldn't be my top choice.  Sempervivum are bomb-proof, evergreen and as low-maintenance as you will find, plus they will absolutely cope with your amount of substrate.

We have the following sedums in our London garden (they have coped admirably with all frosts and the occasional snow).  All are evergreen, unless marked otherwise.

Sedum spathulifolium "Cabo Blanco/White Cape"
Sedum album "Coral Carpet"
Sedum spurium "Dragons Blood"
Sedum kamtschaticum "Weiehenstephaner Gold"
Sedum "Lemon Ball" (not evergreen)
Sedum oreganum
Sedum pachyclados
Sedum pluricaule (not evergreen)
Sedum sexangulare
Umbilicus oppositifolius
Delosperma cooperi
Delosperma "Lavender Ice"
Delosperma nubigenum

Some of the creeping Thymes will probably also work.

strelitzia32

 Sempervivum are bomb-proof, evergreen and as low-maintenance as you will find, 

For some reason, even though I have no problem growing other succulents and have run out of space for haworthia offsets, I cannot for the life of me keep a sempervivum alive. They die of over watering, then under watering, then just die for no apparent reason. I even saved a pup of a dying one, got it to root and grow, got a tiny rosette going and then it promptly died. I've got one left, it's decided to look like its under watered so I'm expecting it to rot through over watering shortly. Then I shall give up!