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A Flower in Disguise

Green Team at Green Roof Technology, - Wednesday, January 02, 2013

By: Jörg Breuning & Samantha Yurek

"A weed is a plant that has mastered every survival skill except for learning how to grow in rows." - Doug Larson

 

Photo Jörg Breuning, Green Roof Service LLC: Hieracium aurantiacum, Orange Hawkweed. Haunted by environmentalists and often branded as obnoxious, farmers and nurseries stamp Hieracium as invasive.

It is all about perspectives, experience and evolution.  Weeds are typically plants growing where they are in competition with cultivated plants or simply unwanted by humans.  However, seeing it from a philosophical point of view any organism has a right to exist.  It is the intention of each organism to multiply, spread and adjust to the surrounding environmental conditions.  This adamant approach has also helped humans to develop and thrive over ten thousands of years.  The word native has become a stereotype of certain plants that should be growing in a particular region.  But with human perspectives being far from uniform, the term 'native' has been skewed over time.  The term is irrelevant when looking at the larger picture of evolution.

An unwanted plant on intensive green roofs could be ideal ground cover for un-irrigated extensive green roofs or vice versa.  Being an outside element, green roofs will undergo natural succession and evolution as described above.  This succession can effect the function of a green roof in the long run for the better or worse.  Ideally, maintaining a green roof helps to guide the plants in a stable coexistence with minimal succession, creating little maintenance.  In most cases it doesn't matter whether the green roof plants were planted intentionally or not.

Un-irrigated extensive green roof designs tend to have extreme conditions; therefore the plant pallet is rather narrow.  It is very difficult for most plants to sustain themselves over decades.  Introducing many of these so-called 'weeds' on to a rooftop environment may prove to be more efficient because of the vigorous growing capabilities.  Yet many factors such as unique weather events during the establishing phase (3-8 years), artificial irrigation, pre-grown nursery trays, excessive fertilization, can be counterproductive in modern green roof technology.

Swarthmore College's Little White Grub Problem

Green Team at Green Roof Technology, - Friday, October 26, 2012
A few months ago we were contacted by Swarthmore College to help identify the cause of a disturbance on the roof.  During a routine visit in August about 20% of a large, upper section of a green roof was completely torn up.  The disturbance occurred in areas where low-growing Sedums, such as S. sexangulare, S. album, and S. spurium dominate.  Areas where taller Sedums, such as S. takesimense, S. kamtschaticum grow were left undisturbed.  

Further investigation located the likely perpetrators.  Numerous white grubs were found in soil.  The likely cause of the Sedums being torn up is from birds scavenging for a snack.  The grubs feed off the roots of the Sedums, weakening their ability to resist the damage caused by the birds.  

Our article about the damage inflicted on the green roof and ways to remediate the problem continues in our Autumn 2012 issue of Green Instance.  The Scott Arboretum of Swarthmore College has also written a summary of the events, which can be seen here.

Most Economic Green Walls

Green Team at Green Roof Technology, - Saturday, August 25, 2012

 Paris Green Wall

 

Some decades ago Patrick Blanc, French botanist working at the French National Centre for Scientific Research and specialized in plants from tropical forests created and introduced a unique design for a vertical garden with real plants (Vertical Garden, Green Wall or Mur Végétal). His simple system or other much more sophisticated systems are based on a consistent water and nutrient supply comparable to horizontal high tide/ low tide (Ebbe/Flut) systems in super-efficient nurseries. These systems often include artificial light and heat/cooling for sustainable growth.

Without being a horticultural expert Patrick Blanc was able to start a new trend utilizing horizontal plant propagating systems applied to the vertical as living art. Maintenance and operational costs of all these wall planted systems are very high and so the environmental benefit is certainly questionable. Typically in less than 10 years costs for maintenance and replanting increase the cost for installation without considering the high consumption of energy and water. 

Today when you fly in to Paris Airport Charles de Gaulle you will see multiple, small green walls - very attractive, lush green with an appealing biodiversity. Closer investigations discovered that these walls the next step of green walls that are super-efficient and extremely low cost for installation and maintenance. The systems at Charles de Gaulle Airport in Paris don’t need any artificial lights, they are completely disconnected from any power and water source and they are very efficient dust collectors. The amazing biodiversity has potential for the highest LEED rating.

Here are a few plants identified:

  • Attractiva plasticifolia (grown out of recycled content)
  • Fakefolia polychloridenses (PCB senct)
  • Metatrashus recyclisa (never green invasive)
  • Ripoffera myclientus `Variegatus´ (native)
  • Hidensia polyestertonia (forever green)

 

Good art reinvented.

Dr. Phil O. Dendron, Bel Air,  August 26th 2012,       

A brief stop at the Baltimore Convention Center Roof Garden

Green Team at Green Roof Technology, - Wednesday, July 25, 2012

by Ryan Miller

This past Friday I traveled into the heart of Baltimore City to visit the roof garden atop the Convention Center.  On the second floor huge floor to ceiling windows frame the roof garden and encourage visitors to take a step out into nature.  With benches and tables scattered throughout the garden, you can tell the owner's intent was to bring people outside, not only to look onto the city surrounding them, but to sit down and enjoy the unique natural environment.

The roof garden was completed in 2010.  Initially, the Convention Center was only going to receive a new waterproof membrane, but the roofing company, Barrett Company, suggested the owners go above and beyond the traditional upgrade and take part of a growing trend, bringing nature back to our urban areas.  I for one am glad the Convention Center owner had the foresight and courage to install a roof garden and did not succumb to the hesitance many property owners do when deciding to go with green roofs.  

Throughout the hundreds of Black Eyed Susan’s in the garden you will see numerous bees flying about.  No need to worry though, they have too big of a playground to concern themselves with visitors.

During my visit, the national Firemans & EMT convention brought in thousands of visitors to the Convention Center.  Many of them took time to eat their lunch and relax in this oasis just two stories up from busy Pratt steet, which you could almost hear none of. 

As I visit other cities I’m jealous of the green spaces they have for people to just relax and take in nature.  I’m glad I visited this roof garden as I now have a place to show off to visitors and colleagues alike.

I plan on adding this roof to our tour of Baltimore City green roofs on September 13th.  Please email me if you are interested in attending this tour, Ryan@hvccb.com.  

Heat Wave 2012

Green Team at Green Roof Technology, - Friday, July 06, 2012

 

The unceasing heatwave gripping the Northeast is quickly moving into the absurd.  With temperatures consistently hovering around 100º F there are few places outdoors you would consider pleasant.  Especially not a roof top smack in the middle of New York City, straddled by an interstate highway. Despite the Extreme Heat Advisory, we decided to send Andrew back to the Park & Rec Building to check up again on the Sun-Roots.  

Andrew was happy to report that the sweat pouring from his brow was more than enough to irrigate the sun-baked Sedums.  During conditions like these we continue to be amazed at the ability of Sedum to thrive in such extreme hot and dry conditions in minimal growth media.  Stressing times like these are good for the Sedums, it develops their hardiness.  It is important not to spoil your green roof plants by irrigating them.  They may suffer a little bit, but they will survive and reestablish themselves even stronger for the next heatwave.  

Engaging the Senses

Green Team at Green Roof Technology, - Thursday, May 31, 2012
By Kat Harrold

   

Photos by ~ Green Roof Technology

When designing green roofs which encourage human interaction it is important to keep in mind the 5 senses, taste, touch, smell, sight, and sound.  

Taste – While the a green roof may be a tough environment for some vegetation to grow, there are still several edible herbs that can provide delicious accents to a meal or tea.  Mint, chives, parsley, cilantro, thyme, oregano and rosemary are just a few edible herbs that thrive on extensive to semi-intensive green roofs. 

 

 

 

 

 

 

Touch – Flowing grasses with prickly seed heads and the fuzzy leaves of Hieracium create a dynamic contrast to the lush springy texture of succulents and sedum.  Small berms can be used to integrate ornamental grass areas into extensive green roofs while keeping weight restrictions in check.

 

 

 

 

 

 

 

Smell – Closely related to taste, many culinary herbs can also employ a richly scented environment.  Other fragrant options for green roofs are lavender, polyantha rose “the Fairy”, sage, and Echinacea Daydream.

 

 

 

 

 

 

Sight – One of the many beautiful things about a green roof is there are a multitude of drought tolerant plants which provide year round interest.  Late winter and spring welcome a blast of color from crocus, Sedum hybridum “Czar’s Gold,” Dianthus, and Allium.  Summer brings forth a variety of extended bloomers including Sedum kamtschaticum, Hieracium, and Telinum.  Fall offers a variety of color from Aster Purple Dome, Snowcap Shasta Daisy as well as a red and gold glow from the foliage of several sedums.  Winter blankets the roof in festive greens and reds.  Sedums kamtschaticum, ‘Czar’s Gold,’ ‘Blue Spruce,’ and spurium ‘John Creech’ maintain their green foliage while Sedum spurium ‘Fuldaglut,’ moranense, album ‘Coral Carpet,’ and rupestre ‘Angelina’ brighten the season with displays of red and gold.

 

 

Sound – Green roofs have the to power to not only clean rain and air pollution but sound pollution as well.  When designing a green roof to function as a patio space, consider using plants which rustle in the wind such as grasses.  The tall reeds create white noise which helps mask the sound of a busy street.   

 

 

 

 

 

 

 

Swarthmore's David Kemp Hall Reaches Tenure

Green Team at Green Roof Technology, - Wednesday, April 18, 2012
By Kat Harrold


Photo ~ By Green Roof Technology

For some, green roofs may seem a novel addition to a green minded institution but to Swarthmore College it was an essential and strategic move.  In 2008 when the college needed to add a dormitory to accommodate its growing student body, there were concerns about the increased run off from the new construction.  Sustainable architecture through green roofs offered a solution that minimized the building foot print making construction of the new dorm possible.  The green roof was spear headed by a few brave faculty, dedicated alumni and students, and Green Roof Technology.  To stay on budget the school chose to invest in a green roof instead of the costly LEED certificate while still building to LEED standards.  This dorm was recognized in 2010 with the American Institute of Architects Housing Award.

The 8,600 sf green roof is the home to many plant species including sedum album murale, sedum spurieum roseum, delosperma nubigerum, and some indigenous plantings.  The green roof also features a raised planting bed for experimental vegetation such as cacti.

The profile of the green roof is a shallow extensive system and has a total profile of 3.5 inches with the growing media depth composed of 2 inches.  While Swarthmore may have a reputation for having the best maintained green roofs in the area, the maintenance required on the roof is blissfully minimal.  To maintain its pristine state Gardener Lars Rasmussen weeds occasionally as needed and irrigates only when drought conditions exceed two weeks.  The roof is minimally fertilized and occasionally cutting back of the overly aggressive plants takes place to encourage more diversity on the roof.

Since its installation the green roof has reduced run off, air pollution, and saved energy on the top floor of the building by as much as 25%.  While the green roof is not available for students to congregate it is open for guided tours and classes and is visible to all from the third floor.









Signs of Spring

Green Team at Green Roof Technology, - Friday, March 02, 2012

By Kat Harrold


Photos by ~ Kat Harrold

 

Sedums may be great for the hot dry climate of the green roof there are more colorful accent plants to consider such as bulbs.

 

Early spring when sedum album is just starting to wake from its winter’s nap Snow drops (Galanthus nivalis) spring forth with their deep green foliage and delicate white flowers.    

Other excellent spring bulb choices are dwarf iris, crocus, daffodils, tulips, and chionodaxa.    As the seasons progress, splashes of color  can be added to the roof with bulbs such as allium and cyclamen in summer and early autumn.  

Many of these bulbs are native to the harsh environments of the middle east and western Asia making them perfect candidates for the green roof environment.

The general rule of thumb when planting bulbs on a green roof is to cover the bulb with 3 times with the amount of growing media as its height with the crown facing upwards.  In other words if you have a 1 inch tall bulb you want to cover it with 3 inches of growing media.  Therefore, larger bulbs will have greater success in deeper green roofs with a 4 inch or greater growing media depth.       
 

Necessary Winter Maintenance for Green Roofs

Green Team at Green Roof Technology, - Friday, January 06, 2012
By Andrew Cole Yanders

 

 

A diligent maintenance schedule is a principal we take very seriously.  Without proper maintenance a green roof has no chance of thriving and looking its best.  There is even serious threat of long term damage to the underlying roofing materials when maintenance is neglected.  There is even a likelihood of an overall failure of the roof’s main purpose, to keep the building’s interior dry.  Because of the grave consequences of not properly maintaining a green roof we continue to insist on a strict maintenance schedule with all our clients. 

Here in the Northeast of the United States winter is upon us and we are eagerly awaiting the first blanket of pristine white snow.   There are 4 key maintenance aspects we wish to highlight that are essential for the health of the roof during the winter season.  

1.    Clearing Drains & Gutters:
Clearing roof drains and gutters is important all year round.  During the winter months moisture accumulates in large volumes on your roof and when the snow and ice melts it places a particular high level of stress on the waterproofing.  If the drainage system of the roof is not operating efficiently, water will find its way through the weakest points of the waterproofing.

To maintain a properly draining roof, roof drains and gutter must be inspected and all debris removed, especially if the green roof does not have inspection boxes.  Because drains without inspection boxes are much more prone to clogs, we believe inspection boxes are absolutely necessary for any green roof system.  

2.    Snow Removal:

Similar to any typical roof, when snow begins to accumulate heavily on a green roof make sure it is evenly spread out; snow drifts should be mitigated to avoid exceeding load limits.  

In areas where snow accumulation on the roof is a hazard particular attention must be made not to damage the green roof during snow removal.  So far as we know, there has been no literature on this subject and no recommendations have been made.  We are recommending a 4 inches, 20 cm, buffer layer of snow.  To remove any more snow allows for the potential to disturb plants and dig into the growing media.   

The best method for removing snow from a green roof is to shovel the snow onto a blanket and drag it over to the edge of the roof, always remembering to leave of 4 inch layer of snow over the green roof.  

 

3.    Waterproofing:

The early months of the winter is a good time to check the nooks and crannies of your roof’s waterproofing.  Check the caulking and look over all the access areas and make sure they are all sealed properly.  Additionally, before any snow has begun to accumulate on the roof, check all areas of the green roof for wind or water erosion.  Alleviating these problems areas in the winter allows for rapid vegetation covering to occurring in the spring and protects the waterproofing layer from any deterioration due to exposure to the elements.  

4.    Pruning & Cutting Vegetation
We are never pleased when grasses are cut in the fall or early winter.  Besides providing a decorative look to an otherwise dormant field, leaving the dry seed stalks provide protection for the core of the plant and its new growth.  




Green Roofs and Facades: A Habitat Template Approach

Green Team at Green Roof Technology, - Friday, September 30, 2011

by Jeremy T. Ludholm

 

Review by Kat Harrold GRP

Great article on using the potential our built environment presents for plant life rather than trying to turn it into an environment it simply is not.  This article explores how we can use plants adapted to rocky surfaces and windy areas to green our cities and our green roofs.   

Are there any rocky areas in a park near where you are?  What kind of plants do your find growing there and how might you be able to create a habitat for them in your built area?



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