Tuesday, May 20, 2014

Native Plant Patterns and Historical Rainfall Trends, Predictors of Green Roof Plant Success

Climate and weather patterns are the most significant determining factors of what plants will go on your green roof project and so, rather than turn on the TV I like to look at historical weather maps.
National Weather Service's Historical Rainfall Maps
Green roof plant modeling process considers light and wind to be the two primary design variables for factors affecting green roof plants.  Sunlight relevance to green roof plants and for that matter even ground level landscape designs is usually referred to in terms of 'Photosynthetically Active (and Reactive) Radiation, or PAR.  Too much PAR and the plants can burn, desiccate and wither.  Too little PAR and the plants fail to grow.

Along with PAR is the photosynthetic pathway of the green roof plant and a host of other survival mechanisms such as photoperiodism, phototaxicity and phototropism.

Wind impact too is a design variable that must be accounted for during green roof plant layout.  Strong desiccating winds can harm green roof plants with as much severity as PAR overload.  Wind can pull so much water out of a leaf that the plant's vascular system will be overwhelmed and interestingly, no matter how much green roof irrigation is added to the planting bed, the plants still die.

Micro-irrigation usually alleviates the stresses of long droughts and so on those green roofs, available rainfall impacts may not be as much a controlling design variable (though still extremely important) as wind and light.

Still I find it very interesting to study rainfall patterns across the U.S. and across the world.  Nature has laid out and sorted the different types of vegetation across our continent in a manner relating to wind light and also according to rainfall amounts.

Yes, it is a simple and very broad generalization to say that following Mother Nature's lead supports project landscape or green roof plant potential success.  

When I look at the above map depicting historical rainfall amounts published by the National Weather Service, I see three main, broad patterns.  The Northwest and the East (red and orange areas) receive most of the rainfall across the U.S.  Broad leaf dicots and C3 monocots fill these regions.  Florida and the Central Plains (green areas) receive less than average precipitation and are vegetated with great stretches of grasslands.  Here in Florida the pine flat woods which make up much of the state are filled with C4 ground cover grasses such as the Andropogons and Sporobolis species (if you live in Pensacola though you may want to choose wetland plants for your green roof due to all the rain they have been receiving lately).  Finally, the areas depicted by the least rainfall amounts (less than 20 inches per year - light blue geographic regions) are inhabited by cacti and other succulents.

So if I were designing a green roof for an area outside of Florida I'd think of this map first.

I may or may not end up following Mother Nature's lead after examine a complicated host of other factors, including client intent and if I choose not to follow then my green roof planting design better be spot on in producing the ecology my selected green roof plants will require.

The roof is a seriously harsh place to grow plants.  Use of Mother Nature's millennia of trial and error as guidelines for selecting green roof plants is smart green roofing.  It is hard to beat local native plants on the roof or across the ground.

Thursday, May 8, 2014

Florida Low Impact Development, A Native Plant Bioswale Success!

The Lasalle Street storm water bioswale is growing into its third spring, a little over two years old.  I know because my aorta dissected during the middle of the project's schedule. Ugh.  A first year plant and project review can be read here while photos and several posts of the original planting project can be found here.
Native plant Bioswale, Lasalle St., Jacksonville, Third Spring's Growth

Today the array of native plants installed by a marvelous group of volunteers has grown into their own prime, lovely Florida grasses, native shrubs and the wonderful cypress tree, Taxodium spp.
The Native Plant Bioswale was originally planted in late 2011
Bioswales are rapidly becoming one of the more popular approaches to cleaning urban storm water runoff and most are using native plant species.  The University of Florida IFAS Extension Service has produced a helpful, informative publication on the design and benefits of urban bioswales for Florida cities.
The Bioswale has matured into a prime example of a successful low-impact development project

We think of plants on green roofs providing many benefits, including;

  • Sequestration of Carbon and mitigation of CO2 greenhouse gasses
  • Positive production of fresh oxygen daily
  • Cleaning rainfall runoff by filtering out particulate matter and attenuating flow rates
  • Uptake and sequestration of nutrients such as nitrogen and phosphorous
  • Habita creation for small to large wildlife and birds
  • Beauty for us humans
  • Urban Heat Island Effect mitigation - cooling of the cities
  • Keeping our creeks, lakes and rivers clean
  • and so much more
Bioswales provide the same benefits as green roofs.  Bioswales are like a green roof but are located directly on the ground instead of a rooftop.
Bioswales, like Florida Green Roofs provide an array of ecological and environmental benefits

Plants are so amazing, especially Florida native plant species.  They work 24/7 to help keep our world clean and that is just the start of what they really do for us!
Lasalle Street Native Plant Bioswale's Third Year Growth



Tuesday, May 6, 2014

Tree Ring Music - Melody in the Urban Core

I love plants.  When I heard about tree ring music on the record player, I had to share it here.  And we do have trees on some of our green roofs, like the Grancy Greybeard atop the Breaking Ground Contracting Green Roof.  I like the Acer music so much.  Enjoy!
For a full listing of tree ring music see Bartholomäus Traubeck's websitehttp://traubeck.bandcamp.com/album/years

Monday, May 5, 2014

Florida Green Roof Plant Root Structure, Horizontal Root Architecture

Green roof plant architecture is an important biomechanical component of all green roof design, construction, installation and maintenance activities.  In the end a green roof is first, foremost and all about the plants.
Florida green roof plant root architecture - beautiful horizontal root structure
Without the happy, thriving plants, there is no green roof.  Possibly a brown roof but not a green roof.

I think the Florida extensive green roof root structure depicted here in these photos is simply beautiful.
Green roof plant root architecture -  horizontal root structure growing into anchor
An understanding of green roof plant root architecture is one of those fundamental design talents that every green roof professional should possess.  Some of you will have learned about green roof plant root architecture from years of observation, hands-on planting and study of how green roof species grow, others through educational programs.  I examine root structure across green roofs every chance I get.  

My preference is shallow soil media and unimpeded horizontal growing space for green roof plant roots.  I do not like sectional barriers that may limit horizontal root growth and ultimately cause root circling-root bound growth patterns.
These grasses possess good green roof plant root architecture - not too aggressive but sturdy
Another reason I prefer unimpeded horizontal root growth opportunity on a green roof is because I believe green roof plants will over time, relocate themselves or their offspring to the best place on the roof for their particular species survival.  Yes, plants do move through root biomechanic mechanisms.  It is poor planning to restrict green roof plant root architecture any more than necessary.  Just think of how many times you may have pulled a plant from a nursery tray or pot with twisted and circling roots that have practically strangled the plant.
An anchor system may keep plants on a roof during tropical storms
In addition to catering to the green roof plant through design of open space for root growth to occur we like to provide the roots an anchor to grow into.  There are many different approaches one can take when providing an anchor, including cables, mesh, netting or fabric.  By permanently attaching the anchor material to the roof you create a green roof plant growing system that may be resilient to tropical storms or cyclone winds.
Unimpeded root growth prevents strangulation of green roof plants
Using this approach we have created green roofs that have stayed in place when blown with 130+ MPH winds.

The grasses in these photos show this principle in practice.  Using a small, mock up green roof growing system these plants have embedded their roots into a nylon fabric, creating an impressive anchoring form of root architecture and growing in a well defined, horizontal fashion.
A good green roof plant architecture will create a monolithic growing mat with plants anchoring each other
While some prefer deep plantings with roots reaching down vertically, we find horizontal root structure strategically places roots in an optimal position to absorb those frequent one half to two inch afternoon rainfalls here in Florida.  Rain water usually stays in the top inch or so of the green roof soil media.  With a horizontal growth pattern, green roof plants can take advantage of this rainfall where deep roots may have less rain reach down into deeper soil horizons.

If you are wondering, the photographed soil media contains less than 5% organic material.  The bark-looking chips are actually ground recycled rubber tires.  This is an experimental soil media, one we do not use on actual green roofs due to fire ratings.

Know your green roof plant architecture.  Remember, in the end a green roof is first, foremost and all about designing a growing system that keeps the green roof plants happy, healthy and surviving in the long term.

Thursday, May 1, 2014

Intense Rooftop Aquaponics - Amazing Rooftop Garden!

Check out this impressive Rooftop Farm - Aquaponics - garden video.  It is amazing just how much food is being grown within a small rooftop area!


Efforts like these are truly inspirational and may hold the answer to feeding the world's future population.