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Green Roof Plant Blog

Intrinsic Perennial Gardens

Green Team at Green Roof Technology, - Tuesday, July 16, 2013

Located North of Chicago, nestled on the Wisconsin-Illinois border, is a wholesale container nursery called Intrinsic Perennial Gardens. Started in 1992, they specialize mainly in one gallon perennials, including ferns, grasses, shrubs, vines and green roof plants.

A Family owned and operated company, Brent Horvath is the current owner of Intrinsic Perennial Gardens. But the family business stretches way back into the 1970s, when his father, Lajos, created Intrinsic Landscaping and his mother, Trudy, ran Flowers by Intrinsic. In 2002, Jörg Breuning introduced modern green roof technology to Brent and his brother, Kurt, of Intrinsic Landscaping. Working together, our companies created the green roof on the Peggy Notebaert Nature Museum in Chicago. Not only is Brent the president of Intrinsic Perennial Gardens, he has recently shared with us a list of his top picks of native plants which would specifically flourish on green roofs. Also in the line to appear on bookshelves in the fall is a book by Brent on Sedum, published by Timber Press.

Geum x Sea Breeze   Photo credit: Intrinsic Perennial Gardens

Intrinsic Perennial Gardens strives to grow the best ornamental plants as naturally as possible. Their unique operation allows them to breed and introduce new plants into the trade. They offer over 900 varieties of species, 50 of which have been selected, bred and introduced into their nursery. They propagate around 80% of their own material. Approximately a third is done by seed, a third by cuttings and a third by division. Included on their 23 acre farm is a one acre field specifically for plug production. 

Early flower on Green Roofs

Green Team at Green Roof Technology, - Thursday, April 11, 2013

Photo Credit: Sempergreen

To spot a crocus popping up from the ground is a sure sign spring is right around the corner. Many varieties of Crocus are the very first to bloom in the season, although there are a handful of varieties that are autumn blooming plants. A part of the Iris family, these perennials have over 80 different species. They enjoy partial to full sun and well drained soils and flourish in hardiness zones 3 through 9. Growing only 3-6" tall, the cup-like flower comes in a variety of colors such as pink, orange, yellow, blue, white or purple. They require little to no maintenance and can be popular with bees at a season where other plants are not flowering yet. In the language of flowers, the crocus means cheerfulness.

Many are cultivated for their flowers appearing in autumn, winter, or spring.

The spice saffron is obtained from the stigmas of Crocus sativus, an autumn/fall-blooming species and could be an interesting crop for semi intensive green roofs or educational urban farms.

Some Crocuses or Croci especially C. tommasinianus and its selected forms and hybrids (such as 'Whitewell Purple' and 'Ruby Giant'), seed prolifically and are ideal for naturalizing on green roofs.

Photo Credit: Sempergreen

The picture above shows Crocuses planted under a pre-vegetated Sedum mat at the Sempergreen facility and below shows them planted in between plants of the Convention Center Parking Garage in Philadelphia among other bulbs.

Photo Credit: Green Roof Technology

Tulipa sylvestris

Green Team at Green Roof Technology, - Tuesday, March 12, 2013


Also known as the woodland or wild tulip, this fragrant, sunshine yellow flower was first recorded in Europe.  Easily naturalized in fields, it can be found mostly in the north eastern United States in hardiness zones 3-9.  Growing anywhere from 4-12", this tulip is comfortable in full sun or partial shade and grows best in well drained soils.  Blooming in mid to late spring, the wild tulip has the ability to clone itself by underground stolons, running horizontally and popping up several feet away.  These runners help this bulbous perennial to spread easily over any landscape. Ironically these woodland tulips have been slowly disappearing in the wild.


Bleeding Hearts for Green Roofs on Valentine‘s Day?

Green Team at Green Roof Technology, - Monday, February 11, 2013

by Jorg Breuning

As beautiful as the Greek name sounds, Dicentra eximia is relatively undiscovered by the Sedum-blinded Green Roof plants experts and by the yearning LEED point collectors. The beautiful flower is native Genus to Northeast United States and Asia that comes in many “faces” (Species and several cultivars).

Dicentra eximaThis plant won’t survive in full sun but will thrive on moisture retaining partially or fully shaded roofs with in a FLL-certified green roof growing media with depths around 3-5 inches.

Leaves are finely divided and gray-green, growing from the base of the plant.

Flowers are pink and bloom in tight clusters at the top of leafless, fleshy stems above the leaves from mid-spring to autumn. The four petals are connected at the base. The two outer petals are pouched at the base and bent back at the tips. The inner petals are perpendicular to the outer petals and connected at the tip. The pistil is enclosed within the inner petals, and the two stamens are on either side. There are two tiny, triangular, pink sepals above the petals.

Seeds are borne in a plump, pointed pod. They ripen to black while the pod is still green. Each has a white elaiosome (Greek élaion "oil" and sóma "body") that is prized by ants.


If the ants would have been a litter quicker in the last 150,000 years these plants would have spread over the entire North America already.  However, with green roofs there is a chance to help nature along in this process.


USDA Dicentra Eximia

A Cool Green Roof Plants Study

Green Team at Green Roof Technology, - Friday, January 11, 2013

Picture: Greenpeace

By Jorg Breuning

A recent British study in Building and Environment found that broad-leafed plants, such as Stachys byzantina, Bergenia cordifolia and Hedera hibernica, which can thrive in partial shade, outperformed the traditional Sedum in cooling the substrate and surrounding air.  The study concluded by suggesting, “…the choice of plant species on green roofs should not be entirely dictated by what survives on the shallow substrates of extensive systems, but consideration should be given to supporting those species providing the greatest eco-system service potential.”1

This is certainly one of the many worthless studies on the web that shows us that no horticultural understanding or common sense was ever part of the research study.  A green roof is all about the vegetation and if we are not entirely dictated to by what survives, we have simply no plants, no vegetation, and therefore no green roof.  It is also not new that more leaf mass provides cooler temperatures – standing in summer in the forest is cooler than on a corn field.  I always thought this was common knowledge. 

The broad-leafed perennials that were tested (less than 2 year tested) typically require deeper soil profiles.  More green roof growing media (soil) increases the costs of the green roof, the structure and the maintenance dramatically.  Substantially increasing green roof costs decreases the likelihood of having a green roof to start with.  The study also did not mention that the climate conditions in Great Britain are unique and are generously supported with moderate temperatures by the golf stream all year around.  This effect allows higher varieties of plants to start with but won’t guarantee a higher survivability of these plants.

Comparing Sedums with the mentioned type of perennials is like comparing wild strawberries with apples. The survivability of Sedums under extreme conditions on a shallow layer of soil with low nutrients makes them to the ideal, perennial and stabilizing groundcover for extensive green roofs.

There is no doubt that we use other annual or perennial plants as temporary fostering or nursing plants or to promote the growth of Sedums or reduce the pressure of unwanted plants. 

In modern green roof technology there are multiple choices of herbaceous perennial plants that supplement the fundamental Sedum carpet.

Botanical Names of Green Roof Plants

Green Team at Green Roof Technology, - Monday, January 07, 2013

A botanical name is a formal scientific name to each individual plant conforming to the International Code of Nomenclature for algae, fungi, and plants (ICN). The purpose of a formal name is to have a single name that is accepted and used worldwide for a particular plant or plant group.

Botanical NomenclatureFor example, the botanical name Sedum reflexum denotes a plant species which is native to Northern, Central, and Southwestern Europe, where it has accumulated various names in many languages. Later it has been introduced worldwide, bringing it into contact with even more languages. English names for this plant species include: Reflexed Stonecrop, Blue Stonecrop, Jenny's Stonecrop and Prick-madam. The cultivar Sedum reflexum 'Blue Spruce' is a blue-green-variegated horticultural selection of this species.

Botanical names prevent people from confusing different species of plants, but also indicate that different species are related. The genus (ex. Sedum) is the unique name followed by the species (ex. reflexum). The first letter of the genus is capitalized and the species in small letters. Most of these names have their origin in Latin or Greek, are combinations of languages or words, the name of somebody who is honored, appearance or location.

Knowing what the Latin (and sometimes Greek) words mean can help gardeners with their planning and maintenance chores. For instance, if the available area is cramped, a plant with arboreum (tree-like) or altissimum (very tall) in its name might not be the best choice.
Some names refer to special characteristics of the plants. Pubi, hirti, villi, and barbi are all "combining forms" suggesting hairiness. Combining forms are Latin roots with vowels added to facilitate pronunciation. They frequently appear attached to more familiar Latin-based words, like those for leaf and flower. Hirtifolia would mean hairy leaved. Barbiflora would mean bearded flower.

It is getting really interesting when we look at cultivars of plants like Sedum reflexum 'Blue Spruce'. 'Blue Spruce' is a blue-green-variegated selection of this species. Variegations of plants can be caused by environmental conditions (air quality, sun light, nutrients, water supply etc.) or by targeted human influence like propagating only the plant with certain properties, propagating plants with “defects” or Gen manipulation (like most of our food plants, ornamental plants or turf grasses).

Vegetation for Green Roofs should be identified, specified and communicated by their botanical name to avoid confusion. The names of the plants must be written correctly according the International Code of Nomenclature and professionals don’t refer to the “Latin” name of a plant – they refer to the botanical, horticultural or formal scientific name of plants.

Recommended readings (Multi-lingual):

•• Zander - Handwörterbuch Der Pflanzennamen / Dictionary of Plant Names / Dictionnaire Des Noms Des Plantes: Dictionary of plants. Dictionnaire des noms des plantes [Hardcover]
•• The Timber Press Dictionary of Plant Names

Recommended readings (only English):

•• Mabberley's Plant-book: A Portable Dictionary of Plants, their Classifications, and Uses [Hardcover] An Aid to the International Code of Botanical Nomenclature

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