Friday, November 26, 2010

Green Roof Plants - Food, Fiber, medicine and Permaculture - Acclimation

Acclimating a plant to typical environmental standards experienced on a green roof is a wise process to follow when designing or planting a green roof.

Dividing Acclimated Thirty Month Green Roof Allium Plants
Roof ecology typically involves harsh, desiccating winds, high heat, humidity (pressure-cooker style), hard freezes and frosts, long periods of drought and flooding.

Plants raised under typical plant-nursery conditions with plenty of irrigation, shade from shade-houses and regular fertilizer feed don't like to be installed on a roof - and usually quickly go into shock, wilt and die.

Green Roof Plants - Sleep, Creep and Leap - 2nd Year Root Development
I compare the differences between  a plant raised and sold in the nursery garden center and a plant growing on a roof to a hike in the local city park replete with water fountains and paved walking trails rather than a hike across Death Valley (Mojave Desert), California.

Yet there are advantages to growing plants on a roof also.  Roofs offer extended growing environments - warmth, more light and more breezes.

But preparing the plants for what they will experience is of major importance.  We call the process of preparing plants for the roof environment - acclimation.

Perennial green roof plants that are herbaceous in nature, like one of our favorite plants, the Allium genus, usually follow the "Sleep, Creep and Leap" saying of gardeners.

Year One the plants seem to sleep - when in fact they are developing strong roots.

Year Two the plants slowly add upper greenery and leaves.

Year Three the perennials begin adding upper leaf mass quickly and spread from their base.

Acclimation of the plant to the roof ecology should begin from the seed sprouting stage and not the adult stage.

When acclimating a plant from juvenile status to the ecology of  a roof, the green roof plant will ultimately have a much better chance at long-term survival.

The photos included here today are of Allium canadense seedlings that are thirty months old - 2.5 years old.  They have been grown in greenhouses with controlled irrigation and raised heat levels to simulate rooftop ecology.

The metabolism of these plants is set for slow growth rate under harsh conditions.  Once installed on a roof, these acclimated plants thrive rather than going into shock.

Each plant has varying genetics and some develop large root masses capable of storing significant amounts of water and nutrients while others developer slower, growing only as precipitation brings water and dissolved atmospheric nitrogen - and we call these green roof plants Carbon Pirate Plants.

I continue to argue that massive irrigation and fertilization systems installed on the growing number of green roofs across the country are really sustainable.

However, with proper planning and plant selection, preparing your green roof plants for a life's journey on a roof will ensure success.

As always, email us with your questions here.

Happy Green Roofing, Kevin.

1 comment:

Vinisha said...

What an exciting experience!/Hilarious! Delightful! True!/wonderful stuff! thank you!
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