Green roofs

August 8, 2009 at 6:05 pm | Posted in Green roofs, Plants, Sedum | Leave a comment
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greenroofGreen roofs aren’t new; they’ve been around for eons as people all over the world used natural materials to build their homes.  Only now, green roof design has evolved to be not only a way of protecting a building from the elements, it’s a source of beauty and also an ecological response to the climatic changes we are starting to experience on our little planet.  To survive and thrive on a green roof, a plant needs to be drought tolerant, but also capable of soaking up huge amounts of periodic inundation such as torrential rainstorms to release it slowly after the rain has stopped; be able to withstand temperatures over 40 degrees Celsius and under -40, as well as high winds, snow and ice buildup, and full sun.  The advantages of Sedum are obvious as these tough plants can outperform any other, as well as having pollen and nectar for a wide variety of insects including butterflies, native bees, wasps and other pollinators and predatory insects.  Just watch any patch of Sedum in full bloom and count the visitors.  Mixed Sedum varieties used on green roofs will bloom in succession for a long time, throughout most of the summer and fall.  Given all these positive characteristics, is there any downside?  Some Sedum species are prone to dieback, and if used alone on a green roof, could leave bare patches.  However, if several species and varieties are used, this will just leave a gap for another variety to fill in.  Even on very thin lean soil, Sedum can create an impressive cover, protecting the roof membrane and lowering the temperature inside the building significantly, while at the same time insulating it from low winter temperatures.  This will mean that air conditioning and heating costs will be lower in a building that has a green roof.  In fact, in Toronto, it’s now mandated that a percentage of all new construction will have green roofs.  What will this mean in the long term?  Look at many cities in Europe where green roofs have been utilized for many years as a heat reduction tool.  Cities can become much more livable with more green space, whether on a roof, as a park or over a parking garage to mitigate storm water runoff. Humans have an atavistic need for beauty, and green roofs – or should we call them colourful roofs? – give us that.  Imagine a whole city, roofed in beauty that attracts and feeds wildlife, as well as giving all the benefits of a garden floating in air.  Now that’s a concept we can all live with!

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Sempervivum

July 30, 2009 at 10:38 pm | Posted in Plants, Sempervivum | Leave a comment
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Hens and chicks, as they’re commonly known,

are drought tolerant, winter hardy, slow spreading

and beautiful additions to the landscape.  Used as

an accent, planted in a rock wall, grouped in a large

container, the give the garden a tropical feel because

of their resemblance to Echeveria and other tender

succulent plants.  They’re not tender at all, in any

sense of the word.  The only thing that can kill

a Sempervivum is prolonged wet conditions.  Their

preferred spot will be dry, well drained soil mixed

with some small gravel and mulched with stones.

Shipped in the dry, they will possibly be shriveled

when they first arrive.  Pot them into a well drained

soil, water once, then put them on ignore for at

least a week.  Soon you will see them perk up and

become the jewels in your garden.  They can also

be planted right into the landscape, however, be

cautious with the small ones, as they can be

dislodged or covered up.  I prefer to pot them into

4″ pots until they root, then move them to their

final spot.

Sedum

July 30, 2009 at 10:26 pm | Posted in Plants, Sedum | Leave a comment
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The many varieties and species of Sedum seem

endless to the untrained eye, with a multitude of

textures, colours and growth habits.  Many are

groundcovers, used in the landscape as a slowly 

spreading carpet under drought tolerant perennials

and shrubs.  There are upright border types such

as Sedum telephium ‘Autumn Joy’ and Sedum ‘Purple

Emperor’ and some that defy categorization, such

as Sedum populifolium.  All have one thing in

common, and that is their ability to withstand

seemingly awful conditions of drought, poor soil

and tough winters.  Most commonly nowadays, 

they are utilized for these characteristics as

green roof plants, grown on the most inhospitable

area to be found – in full sun (perfect!) and in poor

thin, lean soil.  Bloom times vary throughout the

summer and fall, giving an everchanging patchwork

quilt to attract insects such as bees and butterflies

and many birds and other small creatures to the

visual feast.  Sedum is easy to ship to the customer

as cuttings (most economical choice of all) or plugs

which have the best success rate after planting.  In

both cases, the ease of handling and planting, as

well as Sedum’s adaptability to harsh conditions

make this the ideal cover for green roofs.

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