p90106The last green roof that I wrote about was planned, although not in a typical manner. https://tonytomeo.com/2017/11/25/green-roof/ It is still my favorite green roof. Otherwise, I am none too keen on the fad. Very few buildings benefit from green roofs, and green roofs really do take more work than conventional landscapes in the ground.

The sort of green roof pictured here was most certainly not planned. It could have been the result of a an uncleaned gutter. All sorts of weeds can grow in the damp debris that can wash off of roofs, particularly in damp and foggy coastal climates where moisture so often drips from the edges of roofs. This gutter is just a short distance from the beach in Santa Cruz. The willows in the San Lorenzo River are next door.

Knowing what I know about this particular type of willow, I would guess that the cleanliness of the gutter, or lack thereof, was not really the problem. These aggressive willows can germinate in the slightest bit of debris, even under a single leaf that did not get rinsed or blown away fast enough. Once germinated, their finely textured roots are experts at clinging to anything that might otherwise get rinsed away. If there is not enough debris and dirt for them to grow in, they simply collect their own. Now that it has started the process, it will continue to collect debris and expand its root system until it gets removed or ruins the gutter. It seems to have already collected enough debris to share with a few grassy weeds nearby. It is mostly dormant now, and might have defoliated in the rain since this pictures was taken a few days ago. However, if it stays, it will resume aggressive growth as winter ends.

12 thoughts on “Unplanned Green Roof

  1. It’s Buddleja davidii that’s a huge, similar problem across the UK. Nice for butterflies, not so nice growing out of cracks in roofs or guttering.

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    1. This particular specimen is a Salix lasiandra, or one of the related willows that live in the San Lorenzo River next door. They very commonly appear in weird spots such as this. Although Beddleja davidii can do the same, it is not so voracious about it, and for some reason, is uncommon in this particular neighborhood.


    1. Oh, I have heard about Norway maple in Eastern cities. ‘Schwedlerii’ happens to be one of my favorite old street trees in San Jose. It seems to be sterile, or mostly so. Other Norway maples are rare here, and have not naturalized. The chaparral climate is too dry for them to do so outside of landscaped areas.


    1. Pampas grass falling from above is NOT funny! Oh my! When I was a kid, I saw a huge specimen in an upstairs gutter that was ridiculously big! It must have been six feet wide! I can not thin of anything worse, but there probably is something worse.

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      1. Or something rooting into the roof. Pampas grass can do that, although I believe that the one I saw fell off before doing so. My colleague down south grows a few staghorn ferns, and one contains a seedling of Ficus rubignosa. It had been trying to root into his house for years, and he just cuts it back. I finally pulled it out and chucked it.

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    1. I would think that because it is a commercial building, that gutter cleaning is scheduled along with the rest of the maintenance of the buildings and surroundings. I remember from working with a landscape maintenance firm, that many really do not notice such obvious problems, even while working around them all the time.


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