Onion Roofs....fire proofing and edible

I've been rereading my copy of Stephen Barstow's book "Around the World in 80 Plants" before attending his coming talks in Maine and New Hampshire.  On page 247 (for those of you who have this fine book....if you don't, really consider adding it to your get list!) I ran across this picture:


Wow...an onion roof!


Here's a close up:


These are Allium fistulosum, the welsh onion.  They selected A. fistulosum as it can tolerate dry soil and it stores water in its tissues so it helps avoid loosing the house during forest fires.  I wonder how much selection had to be done or if welsh onion seeds from any nursery would be fine.  In one of the blog posts below it is mentioned that some think this form is quite distinct after so many years of selection.  Stephen probably has the roof selected plants in his collection I bet.  Might be a source of seeds from the original roofs???  I'm picturing them finding a great home on some wofatis!

Anyhow, here are some links to Stephen's blog posts on this:
The Roof Onions of Gudbrandsdalen in Norway
New study of old Norwegian roof onions!

Just curious, what other edibles have people found to be good on green roofs?

That is super cool. I reckon leeks would not be such a good choice.

Greg Martin wrote:Just curious, what other edibles have people found to be good on green roofs?

I've seen sedum, purselane, and nasturtium used successfully.

Doubt that onions would do much against forest fires/embers though, they're not bunched close enough and easily scorched. Perhaps inter planting with sedum, etc would work better - mono crop to micro food forest!

F Agricola wrote:

Greg Martin wrote:Just curious, what other edibles have people found to be good on green roofs?

I've seen sedum, purselane, and nasturtium used successfully.

Doubt that onions would do much against forest fires/embers though, they're not bunched close enough and easily scorched. Perhaps inter planting with sedum, etc would work better - mono crop to micro food forest!

I have some tasty wild sedum that might be fun to work with.  On the fire front, I'm thinking that perhaps those picture don't represent the lifecycle and density that the original home owners used.  Here's another picture from that blog showing a high density, but also showing a lot of dried leaves under them.  In the article it said they used to harvest the roof in spring.  I'm picturing them cutting the roof each year that way in order to clear any dry material at the same time.  


One thing about Allium fistulosum is that it's a juicy Allium.  Whenever I cut its scallions they drip a water solution.  I tried to get a picture (below) of that but didn't quite time it well to show how much comes out.  I haven't seen this with normal garden onions (Allium cepa) or with A. fistulosum x cepa hybrids (walking or Egyptian onions).

Camas is another edible bulb that withstands fire and a very dry period in summer.

I think the type of soil will have much more to do with fire suppression , than anything planted.