A Tiny Roof Garden

Jeremy Bartlett's LET IT GROW blog Posted on by

Roof gardenLast August we built a mini “roof garden” on one of our sheds. It faces west, towards the garden, but could also be positioned to face south or east.

First, we made sure that the roof was sound. The old roofing felt was in poor condition, but instead of replacing it with more roofing felt, we fixed sheets of corrugated, bitumen covered roofing on top. These are very durable and come in a variety of colours – we chose green. The roof should now last for many years, as long as the shed, if not longer. We bought our roofing material from Wickes, but it is also available from other DIY stores, such as B & Q.

Next, we built a wooden frame from offcuts of wood, to hold the “roof garden”. Ours is a rectangle measuring just 760mm by 500mm and about 70mm deep. It is fixed to the roof by a single piece of wood about 850mm long, along its lower edge. 70mm of  soil depth is not very much but it suits drought-tolerant plants; you could make it a bit deeper.

We added an offcut of lightweight permeable weed suppressing fabric to the box we’d built and then filled it with a mixture of garden soil and grit. We planted into this and finally spread a layer of fine gravel on top of the soil as a mulch. This looks good but will also stop weeds from germinating and conserve moisture. The box does not weigh very much, so it is easily supported by the shed roof.

As usual, the planting was the best bit. We chose Houseleeks (Sempervivum), Rock or Welsh Stonecrop (Sedum forsterianum) and Biting Stonecrop (Sedum acre). All are doing very well and are flowering as I write, surviving quite happily on Norfolk’s sporadic, low rainfall. Other species of Sedum, such as White Stonecrop (Sedum album), would do well too.

Why not give it a try?

If you want to do this on a grander scale, The Green Roof Centre website offers advice and case studies and Maddy Harland writes of her own experience of creating a Sedum roof on the Permaculture Magazine website.

Roof garden

Tree Tobacco, Nicotiana glauca

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Tree Tobacco, Nicotiana glauca

When we moved house we held a moving in party of sorts, a day in the garden when friends could drop by and see us. Several friends brought gifts, but the biggest and most impressive after two years is a Tree Tobacco plant, Nicotiana glauca, from our friends Mark and Charlotte.

It is a monster of a plant, a big, amiable thug that towers above the fence at the bottom of the garden. It has thick, rubbery blue-green leaves (hence the name glauca) up to 20cm long and it grows as a large, bush, up to about nine feet (2.7 metres) tall. The tubular, yellow flowers are about 5 cm long and 1 cm wide.

Tree tobacco is related to the cultivated tobacco used in cigarettes (Nicotiana tabacum) but differs in several ways: tree tobacco is a perennial, it isn’t hairy or sticky and its leaves are attached to the stalk by petioles. It is a member of the family Solanaceae, which includes some of my favourite plants – some of which I’ve already written about, such as Sticky Nightshade and Henbane.

Nicotiana glauca comes from South America and is an invasive weed in several parts of the world. It has been naturalised in Europe, Africa, temperate Asia, Australia, New Zealand, United States (including Hawaii), Mexico and Macaronesia. In colder climates it can be grown like a hardy perennial, with its top growth dying back in the winter and new growth starting from the base. Here in Norfolk, the last two winters have been quite mild, so apart from some very slight frost damage, our specimen has not been kept in check. Our sandy soil and the sheltered spot in which it is growing will have helped it to thrive. Our plant has a tendency to lean forward so last autumn I cut back one of the shoots, which has tidied the plant up a bit.

The only disappointment is that insects don’t seem to like the flowers. According to the paper ‘Pollination ecology of the invasive tree tobacco Nicotiana glauca: comparisons across native and non-native ranges’ (Ollerton, Watts et. al., Journal of Pollination Ecology, Vol. 12, 2009), the plant is pollinated by hummingbirds in California and sunbirds in South Africa and Israel, where it sets seed by both out-crossing and selfing. But in areas where there are no such birds, such as the Canary Islands and Greece (and Norfolk), the plant still sets lots of viable seed by self-pollination.

Last year I took cuttings from our plant and this year I have raised some plants from seed. So if you want a monster of your own you know where to come.

All parts of Nicotiana glauca are poisonous. In Israel, a 73-year-old French tourist died after cooking the leaves and her 18-year-old grandson suffered slight poisoning. In California cattle suffered poisoning after grazing on the plant. However, ‘Floating Tuxedo’ has documented his experiences of smoking tree tobacco and reports that the dried leaves “smelled like oregano, and people at the Barnes and Noble bookstore cafe gave me funny looks as I rolled it.” The Cahuilla Indians in California used the leaves interchangeably with other tobacco species in hunting rituals and as a poultice to treat swellings, bruises, cuts, wounds, boils, sores, inflamed throat, and swollen glands.

Nicotiana glauca contains two poisonous alkaloids: nicotine and anabasine. (The two compounds are isomers of each other.)

If you want to grow your own tree tobacco, there is more information on the Hardy Tropicals UK and, for the United States, the Daves Garden websites.

Tree Tobacco, Nicotiana glauca

Fox-and-cubs, Pilosella aurantiaca

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Fox-and-cubs

Fox-and-Cubs (Pilosella aurantiaca) has started flowering at the end of our garden. It’s a cheery, cheeky sort of plant, which makes me smile when I see it.

Also known as Orange Hawkweed, Fox-and-Cubs is a perennial which spreads both by seed and stoloniferous runners. Its leaves grow in rosettes low to the ground, so it can survive – and indeed thrives – in mown grassland, such as road verges and churchyards. It is a neophyte which was introduced into UK gardens in the 1620s and had escaped into the wild by the late eighteenth century. It is now found through much of the British Isles. It makes a good garden plant, though only for tolerant gardeners, as it will seed itself into bare soil.

Fox-and-Cubs is a member of the daisy family, Asteraceae. Its leaves and stems are covered in dark hairs. Each of its flowerheads is made up of many orange ray florets. Its orange flowers mark it out as something a bit special – most of its relatives (such as Bristly Ox-tongue, Cat’s-ear and Dandelion) have yellow flowers.

The name Fox-and-Cubs (sometimes written without the hyphens) refers to the way that the unopened flower buds hide beneath those that have opened. The herbalist and botanist John Gerard called the plant Grim-the-Collier (Grimme the Collier), possibly because its hairs resemble coal dust on a miner’s beard. Other names include Devil’s Paintbrush, Orange Hawkbit and Tawny Hawkbit. (Hawks were thought to have eaten the flowers.) The plant’s scientific name is more matter of fact: Pilosella means ‘with small white hairs’ and aurantiaca means ‘orange’.

My photograph doesn’t really do this plant full justice. Fortunately there are some lovely photographs of Fox-and-Cubs on the Wild Flower Finder and Naturespot websites.

Coincidentally, there is a foxes’ den next door and for the last month we have enjoyed watching real foxes and cubs playing at dusk.

fox and cub