Green Roofs Teach Us About Plants

We are always very focused on learning about how plants do on the ground and then using compiled data to determine what plants works best on green roofs.


Yet the reverse is true also!  We can take what we learn from green roofs and apply to ground level landscapes with stunning results!


Really cool when we learn from the Green Roof experiences about those plants who do well without irrigation and in extreme heat & desiccating winds.  Roofs are magnitudes more hostile than ground level planting areas.

Native Plants provide beautiful non-irrigated landscape

Species who have proved themselves on the roof are solid choices for most ground level landscapes.

And there are cost savings too!  Here this planting is non-irrigated (the city approved zero irrigation) yet we have a tropical, lush look from two great native plants, Adam's needle and Little Bluestem. The soil prep was special and heavy pine straw mulch applied. Very green in many ways!  For more on this native plant install click here.


Understanding Green Roofs and Green Roof plants pays many dividends.

Green Roof Irrigation Opportunities, Exploring Water Vapor

Fortunately, there are many ways green roof plants can be provided irrigation water.  First we should utilize native rainfall amounts, second water vapor in the form of dew, fog and air humidity.   Air conditioning condensate can provide a significant amount of irrigation as well.  Finally, rainfall captured in rain barrels or underground storage and cistern systems may be utilized to support plant water requirements.  Grey water too may be used if local or state regulations permit.

I've always been amazed at how much water the air holds.

Several of our past blog posts have addressed dew, fog and water vapor (biomimicry).

This morning as I inspected a recent green roof project, I was awestruck at just how much water was rolling off the solar panels, dripping to the single ply roofing, running across the roof to the drip edge and into the gutters.  Alot of water!

Dew Stream Dripping from Solar Panels

So when we think of green roof design we need to visualize the advantages elevated vegetated plantings have over ground level plants from water laden air exposure.

Nature has provided many plants with fine hairs, such as one of my favorite green roof plants, Yucca filamentosa, a physiological attribute allowing for water collection.

Before we immediately specify irrigation systems with potable water for either primary or backup supply,  lets seriously look at what nature provides.

We may be surprised at just how much water nature is making available.

What Plants Should I Use For My Green Roof?

What plants should I use on my green roof?  I hear this question often.  The answer depends on your site orientation, sun exposure, rainfall amount, location, temperature zone, exposure and a host of other variables.

However I strongly suggest you take a tour around town as a first step in selecting green roof plants.  You will be surprised at what you find.  Look up at the top of buildings, old churches, in roof gutters - especially in older downtown areas.

Some of the most successful low maintenance, extensive and non-irrigated (other than natural rainfall) green roofs have been those pioneer and volunteer native plant species established and growing in gutters and along roof parapets.

If you are serious about understanding green roofs you will take the time to go, look, find, and identify the plant species growing without any additional assistance on the roof of your downtown buildings.

Though these plants may not ultimately be those you use, they will provide a solid understanding of the plant morphology and structure that does well under the influence of the 5 H’s.

Non-Irrigated Green Roof - 1 Year and Still Going Strong at UF Test Center

Call Kevin for more information on your light weight green roofs 904-294-2656.

Green Roofs for Florida - Irrigation required? No!

Now, many green roofs are not garden roofs. They are not full of lush, tropical vegetation with nitrogen fertilizers added and irrigated with water that should be charging our aquifers. The latest argument for irrigation of green roofs - is - it is OK if the irrigation water comes from recycled stormwater. Sounds good, right! But how many of proponents of rainwater recycling actually have had rainwater systems in place for some time? If they do they will tell you that the cisterns are empty most of the time! Yes, we have an annual rainfall amount of well over 50 inches per year, but we also have extended periods of time where there is little if any rainfall.

So the proponents of irrigated green roofs say - use city water backup!

I thought we were in water conservation mode here. Watering restrictions, etc...

Just don't irrigate your vegetated roof. Use native species! The other day on a conference call an engineer referred to the native species of plants as 'Weeds!"

It is all perspective. I like the thought of using native species, not irrigating and still having a great vegetated roof.

The above photo is a test panel at UF that has been sitting in a back lot with less than an inch of soil average for almost a year with no irrigation or fertilizer and is still functioning to drink and clean stormwater and provide habitat for pollinators, etc...

No, it is not Jungle Gardens. But it is a thriving, functioning Green Roof! Remember - there is a difference between Intensive Green Roofs that are irrigated, weight 10 times as much or more and cost ten times as much or more - and require massive structural support - and Extensive Green Roofs that are light weight, non-irrigated, non-fertilized and can be put on simple structures.

Why irrigate green roofs????

Another Reason Not To - Click Here...

Green Roofs, Irrigation, Florida & Hurricanes

Hurricane - High Winds & Non-Irrigation Tests for a green roof test panel. We are collecting data, working with a major university to measure hurricane effects on a non-irrigated, lightweight extensive green roof.

The test panel is a 4' x 10' simulated roof capable of being raised and lowered from a flat elevation to a forty five degree angle.

The vegetated portion is non-irrigated and less than one inch thick.

The panel is being tested under hurricane wind speeds in a wind tunnel. It is also under study for plant growth and survival characteristics under a no-irrigation environment where the insulating qualities are being measured also.

Stay tuned for more information!

Green Roofs in Florida and Irrigation. Is irrigation really necessary for green roofs in Florida?

Here we go again! The draft stormwater manual compiled by the Florida Department of Environmental Protection states that 'Green Roofs in Florida must be irrigated.'

The above statement is simply incorrect and is not a statement we should be hearing from the agency stressing xeriscaping and water stewardship!

I am immediately shut off when I even bring up the topic by many.

Why?

I don't know but it is true - Florida Green Roofs can prosper and thrive even without irrigation.

The roof above has done so beautifully! And in-fact is growing water loving sedges this summer (though I imagine they will die when the dry winter hits) - I suppose birds or the wind dropped seed.

Choose your plants wisely. Plant green roofs to survive without irrigation. Be water wise!