Ever since the garden office was finished I've been panicking about planting up the green roof. What to put up there, will it grow, will it leak, will I fall off the roof? I set aside this morning as 'roof time' and offloaded the kids onto my other half so I could dedicate myself to the task without distraction. And I am delighted to say that I survived the experience without any broken bones and hey, I actually enjoyed it!
When it came to what to plant, I'd originally plumped for a fairly dull sedum matting roof, but after consultations with the wonderful and very helpful green roof expert Dusty Gedge I decided to opt for something a bit more interesting. Dusty's the co-author of a superb guide to green roofs which I'd recommend to anyone wanting to undertake their own domestic green roof project. He advised that providing the roof could take the extra weight (which it could), a mix of sedum and wildflower plugs plus a sowing of annual cornfield flowers was a much cheaper and more diverse option than sedum matting. The idea is that the annuals grow up to provide a temporary riot of colour while the other plants settle in.
The technical stuff (scroll down for me clonking myself on the head with a ladder)
The substrate - a special lightweight soil designed for green roofs - had already been applied by my builers at a depth of around 70-100mm, and planted into that are two trays' worth of plugs (a total of 208 plants) from British Wildflower Plants*: the money was running out by this point, so I scrabbled together various sedums from plants I had hanging around the place, rather than buying in sedum plugs, and I also dug up a few things from my gravelly front garden, including fox and cubs, some kind of veronica I, erm, foraged from a crack in a wall a while back and some sempervivums; plus some chives (regular and some unusual white ones) from the veg patch. Then there's annual cornfield seed mix from Just Seeds sown in between the plugs. I fully expect to be tweaking the selection of plants up on the roof, removing anything I don't like and possibly introducing new plants as time goes by. From my research, it seems that the key to picking plants for a green roof is to choose things that can get by in tough conditions, without much soil, moisture or fertiliser - which translates to me as stuff that can grow in the cracks of the pavement - yes to chives and Briza media, no to anything with a deep taproot.
So the complete list of plants up there is as follows:
- Sedum album 'Coral Carpet'
- Another sedum I couldn't find the label for
- Allium schoenoprasum
- Allium schoenoprasum Alba
- Taraxacum officinale (dandelion)
- Dianthus deltoides (maiden pink)
- Centaurea nigra (lesser knapweed)
- Festuca arenaria (dune fescue)
- Leucanthemum vulgare (oxeye daisy)
- Briza media (quaking grass)
- Primula vulgaris
- Gallium verum (lady's bedstraw)
- Origanum vulgare (marjoram)
- Geranium pyrenaicum (hedgerow cranesbill)
- Viola tricolor (heartsease)
- Lithospermum officinale (gromwell)
- Centaurea scabiosa (greater knapweed)
- Pilosella aurantiaca (fox &cubs)
- Oenothera biennis (evening primrose)
- Cynosurus cristatus (crested dogstail)
- Hypochaeris radicata (common catsear)
- Dianthus armeria (Deptford pink) (more of which in a future post)
- Armeria arenaria (Jersey thrift)
- Tussilago farfara (coltsfoot)
- Sedum acre (biting stonecrop)
- Lotus corniculatus (bird's foot trefoil)
- Leontodon autumnalis (autumn hawkbit)
- Agrimonia eupatoria (agrimony)
- Silene vulgaris (bladder campion)
- Erigeron acer (blue fleabane)
And so to the ladder....
When I was at school I remember one report from my maths teacher which read 'Jane understands the theory but tends to rush which causes silly mistakes'. This one phrase pretty much sums me up. Thus it was with the long, heavy ladder I was manoeuvring into position when, in a miscalculation of Benny Hill proportions, I managed to hit myself on the forehead and knock my glasses off. So given my historic clumsiness, my tendency to suffer vertigo at heights, and the recent head injury, maybe I should have avoided the roof, but you know what? It may have been this head injury, or just the fresh air, or the thrill of being child-free for a morning, but once I got up there, it felt delightful (that may be why I look rather deranged in the photo above). I felt pretty safe, aside from trying to get back down the ladder, which was a bit hairy.
The planting proved a lot more calming than ladder wrangling. I tried to avoid a boring grid of plants, leaving some areas bare and grouping plants in other areas, and ridging the soil to change the depth here and there. So now it's a question of waiting to see how it evolves. I am aiming to take a weekly photo of the roof and put it on Flickr to show how it changes through the course of the year.
*I'd recommend British Wildflower Plants' plug plant selections for green roofs - they were the best value plants I found, and they arrived in good condition. The only downside is you don't quite know what you're getting as you choose between four 'mixes' that include any of a long list of plants, so I ended up with a couple of things I already had, or could have sourced simply for free, such as daisies and fox and cubs.