Monday, December 22, 2008

Why do Living Wall Plants Survive the Cold So Well?

In general, plants used in exterior living walls appear to be more resilient to cold than those flat on the ground. Dismantling one of my oldest walls last night, I was amazed to see one of the cactus plants, Disocactus flagelliformis, not only survive the cold but thrive. Amazingly, most of the literature on the web specifies a minimum temperature of 50 degrees F and clearly warns against frost exposure. Last year we experienced several nights in the low twenties. However the cactus keeps on growing.

With my curiosity peaked, I researched frost, cold and plants on Google trying to sort through the thermodynamics of air movement, heat and cold transfer and the five different types of frost. It seems that as the ground layer of air cools, the warm air rises. So the vertical positioned plants on the wall could actually be several degrees warmer than those plants on the ground. There are several interesting stories of how orange grove owners use helicopters to keep warm air blown back down into orchards in California on occasional nights with freezing temperatures or where frost may become a threat.

Additionally and to my surprise I read where many plants on the ground support epiphytc bacteria growth of Pseudomonas bacteria, a gram negative bacteria that also acts as an ice nucelator. From the available literature it seems that the presence of ice-positive Pseudomonas can actually cause ice/frost to form on the plant surface. Frost damages the epithelial layer, in many instances killing the plant.

There is a ice-minus strain of Pseudomonas also, a mutant bacteria that also occurs naturally that does not possess the ice formation encouraging mechanism that its non-mutant sibling possesses.

Leave it to capitalism to go figure out how to profit on these two types of bacteria. SnoMax - made by Johnson Controls - see SnoMax's website, is a product made from the ice-plus variety and is used for making snow! On the other hand, FrostBan - see article - creates a crop resilient to frost. FrostBan was the subject of many GMO battles during the 1980's and early 1990's.

I don't have the testing equipment to see if my Disocactus cactus had the ice-minus Pseudomonas, or if the plant growing vertically with excellent air flow had just avoided the dispersal of common Pseudomonas.

But the fact that it survives the cold and continues to grow on the wall is another piece in the green roof and green wall plant database we are all developing.

Amazing stuff.

Happy green roofing!

Sunday, December 21, 2008

Sunday Evening Musings, Green Roof Engineered Soils, Succulents for Green Roofs and Pot Shapes

The blog data here is a continuation of my previous Green Roof blog. Feel free to refer back to the site because it does contain alot of information - and I will be posting the same info both here and on the Green Roof for Florida blog for some time.

We use succulents in most all of our green roofs. Succulents are an excellent green roof plant in many different ways. Succulents generally store water in their stems and leaves in significant quantities. Cacti leaves are practically non-existent and most photosynthetic functions in cacti occur in the stems. Succulents have stomata on all green surfaces but at much lower surface densities than most other plants.

Because succulents store water they can survive and in most cases still 'look good' after a significant drought. Another benefit to succulents is one of offering a deterrent to fire through their water filled leaves and stems.

Some other drought tolerant non-succulents such as the sages and grasses produce flammable volatile oils that can add fuel or accelerant to a fire.

Most succulents do not need fertilizer in quantities required by non-succulents. We have seen the base nitrogen content in rain provide sufficient nutrients for many green roof succulents.

Succulents also do well in well-drained soils that will wick and absorb a minimum amount of water.

Today engineered soils, such as the MetroVerde engineered soil blends have taken the place of most 'dirt' on the roof.

And finally, we are now prepared to say in our opinion, the green roof plants we propagate and raise like round rays and pots better than square ones.

After viewing first hand the growth qualities and characteristics of our green roof plants grown from seed in round and square containers, and cuttings in both, we believe the round container has less negative impact on root formation than the square shape.

Although there is not a huge significant difference, we've noticed a definite difference in size and in transplanting issues.

Unfortunately round pots are not as space efficient as square pots.

Has anyone out there seen studies conducted on the difference between square pots and round pots? I'd like to hear from them.

Happy green roofing!

Sunday, December 14, 2008

Flexible Green Roofing Panels - Florida Green Roofs

Why flexible green roof panels? - Because some roofs are curved, sloped or rounded. MV flexible panels also mold themselves to the surface they cover, creating a more efficient seal.

Welcome to the new green roof blog by MetroVerde!

Feel free to add your comments and be sure to stay tuned as we explore the world fo Florida Green Roofs!