Be aware that many times the most hardy species you see growing as pioneer plants in gutters may be exotic invasive species. Yet even with all of the more agressive plants taking over building cracks, walls and gutters, occasionally you will come across an interesting patch of greenery, one that is native and can be used on your nature irrigated green roof.
The Urban Nature blog posted some great photos earlier this week of mosses and other plants growing on rocks and stone structures. Be sure to visit Pescalune's photos here.
Plants are resilient. Provide some plants a two inch layer of gravel, sand or organic matter and they will grow and establish themselves in places most would not expect.
|Nature Irrigated Non-Intentional Green Roof|
If you have the time and opportunity, stop and ask permission to examine the soil contents of the niche where the plants are growing. Ask the following questions;
- Is the growing media sandy?
- Are the plants growing solely in organic compost such as decaying leaves?
- It the growing media wet, damp or dry?
- Does the soil media appear to be well drained or is it in a place where water pools and accumulates?
- How about wind exposure? Are there wind breaks or are the volunteer plants sheltered from the wind?
- Look at light exposure. How much sunlight is available? Is there adjacent shade?
All of these questions (and more) will help build the database of green roofing knowledge you need as a green roof designer.
Learn from Nature.
I've heard some of the most knowledgable European green roof designers say - If it is good enough for plants and bugs (Nature) is it good enough....
Carry your camera, pencil and notepad and keep your eye out for plants in the gutters!
Happy Green Roofing.