Here is a view across part of the green roof, showing how far it has come on since my last Green Roof update. The plants have become establishes, and I have added many new plants which are all thriving in just 7 to 13cm of soil, with only occasional watering – once or twice per month – to help them through their first year.
The secret of success in these situations is to choose plants that grow naturally in hot, dry, exposed situations. In the above picture, middle, foreground you can see Lampranthus cooperi – a half-hardy Mesembryanthemum relative with succulent foliage and bright magenta daisy flowers (which are closed up in the photo). It loves these conditions, although it may struggle to make it through a wet British winter – we will see.
The seed heads here are from the Muscari bulbs that finished a while ago. Top left is a new addition –Dianthus deltoides ‘flashing lights’ – many small dark red flowers over dense dark green (almost black) foliage. In the bottom right corner you can see some crimson stonecrop (Sedum spurium ‘Coccineum’)
Here, biting stonecrop (Sedum acre) is colonising a bare patch of gravely soil. Small fragments dislodged by birds probably, have rooted and started to grow. The main clumps are about to come into flower.
Dianthus ‘Flashing lights’, surrounded by the grey blades of Festuca glauca.
The pink lollipop flowers of thrift do so well in this situation – flowering for weeks on end. The grass to the left is Ponytail grass (stipa tenuissima) with very fine tall blades, held upright, but not stiffly, catching the slightest breeze. The inflorescence is equally delicate, transparent, like a veil.
An experiment that is proving highly successful: On the left – a fern polypodium vulgare, and on the left, golden Creeping Jenny (Lysimachia nummularia ‘Aurea‘). Both of these plants tend to be associated with damp shade, but both are just fine in the extreme conditions of the roof-garden it seems. I have seen our native polypody fern as an epiphyte on old oak trees in Devon, colonising dry stone walls in Wales, and covering the top of the high stone walls of the ruined Abbey at Winchelsea – exposed, dry and sun-baked. So I shouldn’t be surprised to see the five clumps on my green roof putting out new fronds quite happily.
Three recently added plants, left to right: Silver shamrock (Oxalis adenophylla) – blue-green pleated foliage and transparent pink flowers in May; Sedum spathulifolium ‘Cape Blanco’ silver-grey succulent clumps; A red Houseleek (Sempervivum var.) – which is spreading rapidly – it likes the sun and exposed aspect.