Green roofs and walls fascinate

Sean Hogan experiencing some high country natural green roof plants in New Zealand on his recent tour here.

An enthralling talk to Balclutha Garden Club in mid May by Sean Hogan from Portland, Oregan in North America enlightened about 30 people about green roofs or eco roofs .
This is not a new concept but it is exciting to see it being developed on a garage, house, shed, commercial building, public spaces and even house trailers, caravans and bus’ roofs. ‘’It is a nice way to enliven many areas with interesting plants,‘’ Mr Hogan said. ‘’ I have been working on green roofs for a long time and am interested in their aesthetics as well as their functionality.’’

Coming from Western Oregon which is quite dry in summer, leading to a water shortage then, makes it ideal for water conservation methods with green roofs one way to ensure this happens. Portland city on the coast has an increasing number of green roofs as they catch the water and release it slowly, helping it trickle down so easing the pressure on storm water systems in winter.
Europe has been doing this for some time but America is developing its own model. Pioneers and old derelict houses develop green roofs anyway through neglect.
Mr Hogan works for Cistus Design Nursery in Portland, doing planning, design and consultation. When designing green roof gardens he mostly uses a variety of drought loving native plants, specific to the local area. 
‘’We can actually use any plants which are not weeds, poisonous, or cause a rash,’’he said.’’The plants need to be able to cope in dry conditions whether that is for a season as it is at home or for a few weeks as it might be here in New Zealand.’’

A green wall design with fascinating plants and colours creating an artistic effect.

People can create green walls as well.
‘’ This a lot of fun if you have a blank wall,’’ he said.’’ You put some layers of mesh on it with soil in between and press succulent plants in to it to make a collage of colours.’’
They use pumice rich substrate and organic soils along with legumes to build up nitrogen. These gardens have to be able to cope with any weather. The green wall can be any depth up to 15cm, with the roots intertwining and holding it all together. It can be treated as a piece of art.
Drought resistant plants which are suitable and survive well in these conditions include phlox, penstemon, sedum, milkweed, ferns, bulbs, orchids, bulbinella, trillium, epilobium, lewisia, agave, delphinium, salvia, carex, hebe, astelia, iris and yucca.
Succulents and ice plants are excellent as they need very little soil and don’t dry out.
Mr Hogan reminded the audience that the nearest green roof is at the Otago University Psychology building, all planted up with natives. This is an excellent local example of how effective these roofs can be, with visitors welcome by appointment.

‘’I do general garden design but my particular passion is in encouraging people to do green roofs,’’ he said.’’One of the significant green roof buildings is M Financial Building in Portland which covers almost a 30m by 30m city block, which is quite impressive.’’ 

M Financial Building in Portland with an impressive green roof.