A greenroof for our bike shed

It's amazing how many jobs there seem to be in the garden as soon as we get a bit of sunshine - jobs and neighbourly encounters over the garden fence!

Number 1 on the list for our garden this weekend was to plant up the roof of the bike shed my husband made back in October. I have loads of wood left over from the various show gardens that I've done over the last couple of years so we were able to build a very sturdy shed - clad in the flooring from my conceptual garden Picturesque at Hampton Court and strong enough to hold the weight of a green roof.

'Picturesque' @ Hampton Court Palace Flower Show 2011 (Gold)

Re-used flooring from 'Picturesque' used to clad new bike shed!

I've done a little research into planting green roofs as last year the RHS invited me to build a roof top show garden at the London Plant and Design Show, and the garden I designed used green roof style planting within the terrace. I used plants that would survive both the harsh conditions that roof top gardens contend with (high exposure to wind and sun) and being planted in only 10cm of soil. I used hardy, drought resistant plants that were also evergreen so that the garden would look good all year round and also because the show is in February and I needed the plants to look good then! Planting in this depth of soil is known as an extensive green roof - there are two other types - Intensive where you plant in at least 15cm of soil and semi-extensive, which can be a combination of the 2

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'Sky Green Living' @ London Plant and Design Show 2011 (Silver-gilt)

Like the show garden, our bike shed falls into the extensive category and we have about 10cm of soil to plant in. I kept most of the plants from the show and although some were planted up last year, many are still in the 9cm pots I bought them in over a year ago and have dealt with drought, lack of food and the recent freezing conditions. I feel that if they can survive that - they can survive anything! I've used a lot of Armeria maritima which has self seeded over the last year into our Breedon gravel path - which is a pretty hostile environment, and when you see if growing out of cracks in a windswept cliff down by the coast or growing out of sand dunes - see Colin Roberts' winning entry for International Garden Photographer of the Year , you know it will be ok in 10cm of compost. The other plants I have used are Ballotta pseudodictamnus, Stachys byzantina, a variety of Thymus' and some Alpine strawberries (which, at the moment I have covered in polythene until the risk of frost has passed). I mixed up a substrate of home made compost, shop bought, peat free, multi-purpose compost and potting grit.

Although the bike shed roof would take my weight, my daughter did the majority of the planting as it was much easier for her to manoeuvre about up there and more importantly - she was keen to help. Here she is carefully transplanting some of the 'saved' Armeria seedlings from our path (if you're worried about the Armeria seeding everywhere just pick the flowers off as they come - although the seedlings were very easy to pick out).

A couple of books that I found really helpful were Planting Green Roofs and Living Walls by Nigel Dunnett and Noel Kingsbury and Small Green Roofs by Nigel Dunnett, Dusty Gedge, John Little and Edmund C. Snodgrass. I got a lot of advice from Kay at Oxford Green Roofs - they are a great company to contact for advice on green roofs and definitely worth talking to if you're considering having a green roof on any part of your house.

The Shed after planting - February 2012