Green roof

[John85]

What plants would you recommend for a green roof that is in the shade due to overhanging branches of a big oak that cann't be cut.
The rooting medium (very good soil+beads of expanded clay) is very shallow:5cm(2'') and will be dry during the summer.
I think geranium  macrorrhizum and X cantabrigiense will cope.Any other suggestions? But please not grass.

[Maren]

House leeks; they have the added benefit of bringing you luck. Many of the ancient cottages (300 years old in some cases) in the countryside here in the Chilterns have a few house leeks growing on the tiled roofs with just a bit of soil that came with the plants, and they thrive and do their good work.

[John85]

Unfortunately it is too shady for sempervivum,jovibarba or sedum that are usually grown on a green roof.Another suggestion may be?

[Darren]

I think it depends to some extent on your location John. Here in NW UK where we can expect some (!!) summer rain I'd be tempted to try something like Cyclamen hederifolium which is usually happy in dryish shade. If you can expect weeks of drought each summer then this might not succeed.....

Our own green roof is in full sun but we are still tempted to try the cyclamen.

[Maggi Young]

What about some mossy Saxifrages?
I'd also use some of the little geraniums, the sanguineum types ... here they will do well in shady and hot spots.
Galium odoratum is lovely and should cope well with the situation you describe.

I'd also be inclined to scatter seeds of the' blue and yellow perils'... that is Sisyrinchium bellum  and S. brachypus... they will grow just about anywhere and I have found them to be as happy in shady spots as sunny ones and they do not need deep soil. Their grassy foliage will add texture to the look of the roof planting and they are slef sustaining by their seeding habits.

John, this shady roof project seems very exciting to me!

[Darren]

Great idea about the sisyrinchiums Maggi. Lovely in a confined space like this and indestructible.

How about Chiastophyllum oppositifolium? This likes shade and is succulent so able to withstand dry spells.

[John85]

Darren
Cyclamen hederifolium grows fine here.It only starts to grow later than in Britain usually, depending on the first autum rain to start .
Chiastophyllum is too much appreciated by the slugs to risk it on a roof!
The other side of the roof is in full sun  so if you have a plant that grows particulary well other than the usual succulents ,I would like to know.
Maggi
I cann't grow mossy saxifrages here:The blackbirds tear them into pieces immediatly.
Till now ,I have always grown the G. sanguineum cvs in full sun but I'll try them in the shade.I'll definitely try the sisyrinchiums and the galium odoratum.

Other suggestions are welcome as the roof is 12m(37')long!!!Thank you all.

[Maggi Young]

Other suggestions are welcome as the roof is 12m(37')long!!!Thank you all.

Oh, right, LOTS of suggestions... and seed needed for you then! 

[alpines]

Having spent most of the past 5 years in the dark (walking around the woodlands of Appalachia) there are some wonderful low-growing plants that would be worth trying.
Houstonia caerulea
Epigeae repens
Claytonia virginica
Anemonella thalictroides
Viola rostrata
Phlox stolonifera
...to name but a few. They are all low-growing shade plants that will take some sun and don't mind the rain......and have interesting foliage when the flowers are  over.

[Lesley Cox]

Epigaea repens wouldn't have occurred to me but now you mention it, I think it would be ideal. Shade loving, can cope with quite severe drought, evergreen, very low and flat and with fragrant flowers. It and so many other creeping plants almost make their own soil once they get going, from dead leaves and other stuff blown into or about their mats.

We'll want some pictures John, once the project gets underway.

[zephirine]

Dry shade evergreen groundcovers like Wadsteinia ternata and Vinca minor might do.
Other suggestions: Alchemilla taurica, arum italicum, anemone nemorosa for spring.
Potentilla could be worth trying too.
 

[Stephenb]

Here in Norway, Allium fistulosum (Welsh Onion) has traditionally been used on old turf roofs in the driest part of the country. This onion outcompetes the grasses on the driest south facing part of the roofs, but it's the grasses that win on the north side. I once saw it thriving also on a north facing roof, but it was overhung by a large birch tree which made it drier than normal.

Try Google Translate on this page: http://www.otta2000.com/Diverse/Pipeloek/pipeloek.htm

In Canada, Allium cernuum has been successfully trialled on green roofs.

You can also harvest the spring shoots....

[fermi de Sousa]

Iris tectorum? It is called "the roof iris" afterall
cheers
fermi