Thursday, July 14, 2011

Green Roof Weeds, Maintenance and Taking Care of Plants on the Roof

This is an update of a post I wrote about two years ago.

I was asked to contribute towards a new municipality green roof regulatory policy, one where there was considerable incentive given developers towards site entitlements if the project would include a green/vegetated roof.

One of the committee members also invited was an accomplished technical/construction specialist - one with multiple graduate degrees in technical and mechanical fields.  But she did not understand plants.

Her past green roof projects had been designed around available landscape plants.  Choose the typical on-the-ground landscape plant and design irrigation and fertilizer and other accessory design criteria to support the landscape plants - was the motto.

Whenever we'd discuss native species or volunteer species showing up on the roof, she'd immediately try to quash the discussion by shouting 'WEEDS!  NO ONE WANTS WEEDS ON THE ROOF!'

I think it was because she felt uncomfortable trying to work with the organic, dynamic complexities of nature.  Obviously she wanted no part of having native wildflowers or grasses on the roof.  Moreover, I've seen some of her 'landscaped' green roofs and they quickly revert back to natives, or as she calls them 'weeds'.  I am sure the selective herbicides are used quite often.

We must stop seeing masses of green and train ourselves to look at the plant.  There are few if any true weeds in nature and on green roofs.

Each plant has its own beauty and purpose, even those obnoxious ones.

I've often quoted Lydia Cabrera in saying "there are more spirits in the plants/forests than in the sky'.

The vegetated roof in Sanford I toured this week was full and vibrant due to volunteer plants.

There are no weeds.

I learned this from my daughter, today.  Though I knew it long ago.

She showed me her photos of one of the most obnoxious plants in my book - Bidens alba (Hairy Beggar's-tick).  Just try walking through a mass of Bidens and wait till you come out the other end of the patch....

I love their masses of white flowers but distrust their desire to bestow me with masses of aggravating seeds.

I almost at this time of the year agreed with the self-centered technocrat who probably couldn't tell bamboo from horsetail or coral honeysuckle from trumpet vine.  I almost shouted WEEDS!

But Jincy showed me her pictures from today.  Ones she and Ruairi took out back.  The Bidens are growing on the roof too.

And Lydia Cabrera is right about more spirits in plants.  And I am right about 'there really are no weeds'....

No need to weed green roofs.  Just step back and admire the Bidens.

Green Roof Beauty - Not Weeds - Bidens alba providing habitat and foraging
Green Roof Wonders - Not weeds, Bidens alba provides nectar

Happy Green Roofing!



Brendan Gertner said...

The weeds actually made the green roof look even more natural! Besides, most green roof plants are self-sustaining, so there's no need to fear that the weeds will take all the nutrients. There's plenty of rainwater to go around, as well.

Kevin Songer said...

You are right Brendan - weeds do look more natural - native plants can be very beautiful. A good green roof designer will use those plants that are acclimated to an area.