Thursday, January 29, 2009

Plants for Green Roofs in Florida

Wow. I drove to Tampa from Jacksonville this week and witnessed first hand the damage last week's twenty degree F temperatures did to horticulture across the state. We must all remember that even south central Florida may be subject to hard periods of cold, freezes and frosts.

Balance. The word that kept popping up in my mind was 'BALANCE'. In designing a green roof for Florida we must keep in mind the 5 H's (they have grown to five from my initial three) - Hurricanes, Heat, Humidity, Heavy Winds and Hard Frosts.

Choose your planting scheme to include three components!

Number One - use the standard green roof plants that survive no matter what. These include plants that come through hard freezes and boiler-type humidity periods. There aren't many of these but there are a few...

Number Two - Select some of the Sedums that will thrive in the winter. They will limp through the summer though. Their poor summer performance can be offset by Number 3.

Number Three - Select those plants that thrive in the summer monsoons but limp through the winter.

A good green roof plant designer will be able to deliver year-round color and interest.

Remember - we focus on non-irrigated Extensive Green Roofs. Roofs that are light weight - no more than a couple two or three inches think.

Florida is tough on Green Roof plants.

Hands on experience through many years or trials is what will produce the best design for each Florida location.

Happy Green Roofing!


Wednesday, January 28, 2009

Propagating Green Roof Plants for Florida Green Roofs

Propagating plants for green roof projects here in Florida is an important component of a successful Florida GR project.

Knowing a plant was raised in the same ecotone where it will ultimately be used is important. This not only secures LEED credits for local material use (and other credits) but it helps in knowing the plant can survive local climatic conditions.

My general rule of thumb is that, here in Florida, a green roof plant should be grown no greater than 150 miles north or south f the project physical location - no general limit on east/west other than the local limits for LEED credit.

The roots shown on the succulent leaf here developed on their own, on a leaf dropped as mother plants were being pruned, a testament to the hardiness of plants. The above pictures also show the importance of saving pruned plant material for propagation - and in doing so being a good steward of resources.

Happy Green Roofing!

Wednesday, January 21, 2009

Florida Green Roof Project Continues with the addition of more cold tolerant yuccas....

The New Florida Green Roof Project is moving forward! We've added several new cold hardy varieties of Yucca! Stay tuned for more pictures!

Hard Freezes and Florida Green Roofs - Winter (Hard Freezes - one of the many 'H's GRs face in Florida)

Judy and I have been scurrying most every afternoon to cover plants as temperatures have been dropping into the twenties here in Jacksonville. Looking at the Weather Dot Com it appears that around Tallahassee the mercury has hit the low twenties several times. Walking by our green roofs, I look up with frost blanket in my hand and want to climb up and cover the plants. But I don't.

Our green roofs serve as our best trial panels as we've said many times before. I have finally reached the confidence level that allows me to know the plants will survive. Still though, many of the plants on our green roof are hard to find varieties and the cold north winds are desiccating, unrelenting and potentially fatal to humans, animals and plants.

I am always proud the next day to see the plants stand straight and soak up the sun's warmth. Balancing the choice between those plants, like the sedums that can tolerate extreme cold but melt in the fierce pressure cooker like humidity laden summer heat - and the succulents that can take the tropical heat but not the cold has been the key to success.

There are not alot of plants that fit into the category of withstanding both of the above limiting factors. Then you add long periods of drought and long periods of innundation to the model as inputs and the list of plants that will survive shrink even more.

Finally add the requirement the plants must still look good and not be dormant to the above and the list really becomes small....

So as I await days light to see what damage, if any has been done and add the findings to our resource base - I hope the coldest night so far of 2009 will produce the same positive results as those before.

Happy green roofing in Florida!