Like other green roof companies, LiveRoof Global has a story of conception and evolution; and for us it began with my interest in low maintenance ground covers. During my “writing years” I wrote four books on the subject and my Michigan-based perennial plant business, Hortech, Inc., grew sedums (and other ground covers and perennials) for two decades before entering the green roof industry.

After being in the perennial/ground cover business for twenty years, something unusual happened; Felton Gross, one of our long-time truck drivers, returned from a delivery trip and said “You’ll never guess what they’re doing with our plants”. He went on to tell me about seeing plants planted on a residential rooftop in Traverse City, Michigan. Out of curiosity I went to see for myself, and found it fascinating. Then I began to read up on green roofs and green roof plants. Shortly thereafter Hortech was contracted to grow 250,000 sedum plugs for the Ford Dearborn 10-acre green roof, and that really piqued my interest!

Based on these experiences Hortech published a list of suggested green roof plants (in our catalog) and soon the phone rang with a landscape contractor from Chicago saying “We need you here tomorrow”. He didn’t say why, but I went, and what happened there changed my business dramatically. The landscapers told me; “we’re starting to do a lot of green roofs, and we have a vision for a new way, but we can’t figure it out, so we’re turning to you”. Two hours later, armed with their “vision” and a suggestion from one of their managers (to look at a portable soccer field module, in his backyard) I sketched up a prototype, which I cobbled together the next day.

Soon, with the prototype in hand, I began making sales presentations and was pleased to get a couple of orders. And, from these experiences I sensed a broader opportunity than just Hortech supplying the Great Lakes market. So, having many long-term horticultural friends (other nursery owners), I shared my vision for a LiveRoof® network of horticultural professionals, and quickly assembled the LiveRoof® Global Network, which serves North America and a few other parts of the world.

Since then we’ve been innovative in many ways; developing a family of products such as RoofEdge edging, RoofStone pavers, Lite and Deep soil systems, RoofBlue water retention and detention accessories and, perhaps most surprisingly, plants. Yes, we have been developing plants specifically suited to green roofs, first Sedums and now others.

Here is a picture of me sharing information about these custom grown modules during a tour held during the Grey to Green conference in Grand Rapids. Photo: Steven Peck

As a horticulturist, when we got started with green roofs, I thought I knew which plants would work best, especially Sedums. I’d always been fascinated by Sedums and had quite a bit of experience with them. But, as I gained experience with green roofs, I quickly learned that the rooftop is a very different growing environment than the “ground level” landscape. Sedums that I knew to be durable and persistent in the landscape, didn’t always perform well on rooftops. So, I plowed under the poor performers (literally acres of them) and began cross-breeding the best performers (and selecting variations from them). Next, I tested these plants for a couple of years, on a rooftop with no irrigation and full exposure to wind, sun, heat and cold. And, after that, I took the best of these and made further crosses and selections in order to raise the bar even higher. Today, the vast majority of our sedums came from this process, which was arduous but also fascinating to see what could be unlocked from the DNA of this unique genus of plants.

Today I still cross breed Sedums, but at a slower pace. I think we’ve accomplished most of what I envisioned (plants that resist climatic extremes, smother the soil for low maintenance, and persist indefinitely). Now, with today’s increased focus on biodiverse green roofs (typically irrigated and with 6–8-inch growing media depth), I’ve turned my attention to native plants; and this has brought me back to the time when those landscapers said “we’re doing this, but we envision something different”. The “something different” I envision is based on my experiences and perceived challenges with native plants and biodiverse green roofs. Here is a little background.

Over the years, through Hortech, we have grown native plants for restoration projects as well as landscape and garden center sales. And, unfortunately many times these plants have failed to please, failed to sell (lacking consumer appeal) or failed to be maintainable (by typical maintenance contractors). Even with an emphasis on “habitat and pollinator support”, truly feel-good topics, we have experienced frustrations in their acceptance. The consumer often sees these plants as messy, floppy, weedy-looking and difficult to maintain. On green roofs, we’ve encountered the same. It has been common for owners (of biodiverse green roofs), to ask us to point out the “weeds” versus the “plants”. We’ve had calls asking us to “fix” or replace biodiverse green roofs, and when this has happened, it inevitably has stemmed from a mis-match between the reality of biodiverse “native” plantings and a romanticized image in the mind of the property owner. The owner expected a lush, colorfully and continually flowering meadow, like you’d see on the cover of a romance novel or packet of wildflower seeds. What they received often has been short on flowers, long on sedges and short grasses and lacking seasonal interest (from both flowers and foliage).

Biodiverse roofs like these can be disappointing to property owners who are expecting a full season of color. Photo: David Mackenzie
What can be done about this disconnect between customer aesthetics and a desire for biodiversity? Photo: David Mackenzie

My vision to bridge the disconnect between the “reality” of a biodiverse native-species green roof, and the property owner’s expectation is to provide a collection of plants that is easy to care for and visually appealing (to the property owner), yet biodiverse and habitat-supportive of a broad range of animal life. With biodiverse green roofs, as well as biodiverse landscape plantings, I believe we can straddle the fence, per se, and deliver a functionally biodiverse plant community that is also visually appealing to the “property owner” (throughout the growing season). But, to do so, we may have to set aside some of our native plant “idealism” and broaden our plant palette to be a blend of native species, nativars (cultivated varieties of native species), native hybrids (crosses between two different species), and a few choice “adapted plants” (plants that do what we need them to do, regardless of their place of origin). Furthermore, we may have to change the way we arrange the plants; probably with more planting in complementary and contrasting groups, rather than mixing the plants randomly. People, in general, seem to prefer an element of organization (and control), and in many cases equate designed landscapes to a higher level of beauty. Such famous landscape designers as Wolfgang Oehme and James van Sweden (both deceased) and Piet Oudolf figured this out and have done amazing work when arranging plants in naturalistic groupings that complement, contrast and flow visually. I personally love their design styles, find them much easier to maintain, and encourage others to view their designs on-line and in their publications (all have published books).

Naturalistic planting style utilizing small masses of plants grouped together with color and textural contrast. Photo: David MacKenzie

Native Species

Some well performing native species that we commonly use on green roofs, that have strong visual appeal, include such plants as Lanceleaf Coreopsis, Coreopsis lanceolata, Orange coneflower, Rudbeckia fulgida, New England Aster, Aster novae-angliae, and Large-flowered Beardtongue, Penstemon grandiflorus. All are particularly colorful and long blooming, and employing them more generously and in groupings will likely make green roofs more visually appealing to many property owners.

Coreopsis lanceolata, a native with a long bloom season and ideal for Intensive green roofs. Photo: David MacKenzie 


Horticulturalists and botanists select and develop nativars (cultivated varieties of native species) for various reasons; disease resistance, more vigor, less vigor, taller, shorter, growth habit (e.g., vase shaped, skinny, wide, upright), flowers (color, height, shape, size, density and bloom time), foliage (color, height, shape, size, density and fall color). When it comes to plants for green roofs, nativars can potentially enhance the visual appeal of a planting, and in some instances, nativars may actually support pollinators better than their parent species (research indicates that pollinators may prefer comparatively taller plants with larger flowers borne in greater density; traits that nativars often exhibit). Outstanding nativars include Boltonia asteroides `Snowbank’, a more compact, less floppy, heavier flowering version of the species, Amsonia ciliata `Verdant Venture’, a taller, more robust and heavier blooming version of its shy parent, and Panicum virgatum Smokey Rose®, a compact, rosy-pink flowered, non-flopping version of its taller often-floppy parent species. Smokey Rose® is an example of a nativar that I selected with a vision for making habitat-rich green roofs more desirable. It is intended to resist the elements and stay upright (through compact habit and sturdy stems), to look non-weedy and “pretty” (via tidy appearance and enhanced color), and to be long lived (as it appears resistant to rust, which often plagues Panicum).

Panicum virgatum Smokey Rose® 2 ½’-3’ tall Typical Panicum virgatum 5-6’ tall  Photo: David MacKenzie

Native Hybrids These are plants that result from crossing two different species of plants, sometimes two native species, and perhaps a native species and a nonnative species (this is in the eye of the beholder). This can be done for the same reasons as listed above with nativars, and may be particularly effective at increasing vigor, inducing disease resistance and reducing seed viability (therefore reducing weediness). Examples of native hybrids include Agastache x `Blue Fortune’, a sterile cross between A. foeniculum (a U.S. native) and A. rugosa (a Korean native), ‘Blue Fortune’ is magnificently floriferous, drought and heat tolerant, very long blooming, and potentially more supportive of hummingbirds, butterflies and bees than either parent. Likewise, Rudbeckia x `American Gold Rush’, a cross between R. missouriensis and R. fulgida var. deamii (and potentially a third species) is compact and floriferous, and perhaps most importantly, resistant to Septoria leaf spot. And, finally, Monarda x `Mojo’ is an example of crossing the shorter and mildew resistant M. bradburiana with M. didyma, a taller more florific species. The result is a plant that is intermediate in height with good mildew resistance and numerous, large, upright purplish flowers. It blooms a bit later than M. bradburiana and a bit earlier than M. didyma, and therefore may contribute to a more consistent supply of nectar and pollen.

‘Blue Fortune’ showing hybrid vigor A. foeniculum, a parent of and higher bloom density. A. x `Blue Fortune’. Photo: David MacKenize

*Adapted Plants. The term adapted plant applies to a plant doing what you need it to do, in a particular environment, without regard to where the plant or species originated. It’s an odd term as the plant has not adapted to anything; the plant simply brings what the plant is and does. I think “suitable plant” might be more descriptive. At any rate, some very good “adapted” green roof plants include Walker’s Low Catmint, Nepeta x faassenii `Walker’s Low’, a colorful, reliable and florific cultivar that performs well on semi-intensive and intensive green roofs, and supports a host of pollinators. Purple Moor Grass, Sesleria autumnalis, is a drought tolerant, tidy, upright growing 1 ½ foot tall grass with attractive flowers and foliage, and Geranium Azure Rush®, known for a very long season of bloom and attractiveness to butterflies, which arose as a spontaneous mutation of Geranium x `Rozanne’, a very popular hybrid cultivar. Most significant among the “adapted plants” are sedum species and cultivars, as these make up the majority of green roof plantings. According to LEED, an adapted plant is a plant that reliably grows well in a given habitat with minimal winter protection, pest control, fertilization, or irrigation once their root systems are established.

A biodiverse green roof of Nativars, Native Hybrids and Adapted plants. Customer acceptance is key to the proliferation of biodiverse green roofs. Photo: David MacKenzie

What really are our goals? Each green roof provider has its goals, as does our trade organization Green Roofs for Healthy Cities. My goal and my hopes are that we can cover as many rooftops as possible; “Any green roof is better than no green roof” is my mantra. The value of green roofs includes habitat, of course, but also cooling, energy conservation, extension of roof life, healing (mind, body, soul), civility and social equity, safeguarding lakes and streams from contaminants and excessive heat and conserving community resources (i.e., reducing the cost of sewage infrastructure). I would not want this “buffet of benefits” to be compromised by being overly idealistic about or restricted in the pallet of plants that we use.


While I don’t purport to be an ecologist, entomologist or ornithologist, as a biologist, horticulturist and long-term-thinking business person, I have a passion for conserving and expanding the natural world (plants and animals). And, of course I understand that if the curators of a natural history museum want a meadow on their rooftop, they would likely be unhappy with anything other than native species indigenous to their locale. However, there is everyone else; and those people generally envision a planting that is quite dense, highly and perpetually florific, low maintenance and naturalistically designed. If we can deliver this by using a broad palette of plants and utilizing elements of design, I think we’ll have a broader market for biodiverse green roofs and therefore install more green roofs and provide more rooftops with a “buffet of benefits”.