One of the most exciting presentations at the 2016 Cities Alive Conference for any plant person was by Kirk Laminack, Moore Farms Botanical Garden, Lake City, South Carolina. Kirk is running trials of plants that will work for southern green roofs.
He seeks plants and green roof plant palettes that will take hot, humid summers and mild winters. Most importantly, they’ve got to look good and provide a pleasing aesthetic. There’s another catch: Plants must be easily obtained in the nursery industry, he said. Sedums, the hands-down No. 1 green roof plant in more northern climates, aren’t included because of Kirk’s past experience.
The trials are conducted in 12 constructed test plots measuring 3 ft. x 10 ft. x 15 ft. with 4- and 6-in. media that meets green roof industry standards. Irrigation, Kirk says, is necessary for southern green roofs. Moore Farms’ green roof trial irrigation runs year round, unless it’s raining. Volume delivered is 0.05 in. per irrigation cycle, with the hottest months receiving three daily irrigation cycles and the milder months receiving two daily cycles. There’s no runoff from irrigation. Plants are purchased out of existing inventory from the nursery trade, so often, they’re in larger container sizes, not plugs.
Here’s a list of the 22 types of shrubs, groundcovers and perennials.being tested and the sizes that were purchased.
- Baptisia Carolina Moonlight (1 gal.)
- Chrysogonum virginianum (1 qt.)
- Cuphea glutinosa (32s)
- Eragrostis chloromelas (32s)
- Ilex vomitoria Nana (3 gal.)
- Lagerstroemia Cherry Dazzle (3 gal.)
- Lantana camara Chapel Hill Yellow (1 gal.)
- Liriope John Burch (4 in.)
- Muhlenbergia Pink Flamingo (32s)
- Nandina domestica Gulf Stream (1 gal.)
- Nepeta racemosa Walker’s Low (1 gal.)
- Panicum virgatum Northwind (32s)
- Penstemon barbatus (plugs)
- Phlox subulata (32s)
- Rosemarinus officinalis Huntington Carpet (1 gal.)
- Rudbeckia maxima (32s)
- Ruellia elegans (1 gal.)
- Salvia leucantha Santa Barbara (1 gal.)
- Schizachyrium scoparium The Blues (1 qt.)
- Spiraea japonica Goldmound (1 gal.)
- Talinum Kingwood Gold (32s)
- Vitex angus-castus Blue Diddley (plugs)
Measurements include weather, plant height and width, plant growth, appearance and density. In addition, he records the percent canopy cover for each structure. Lake City on average receives 46 in. of rain annually. Some of that generally arrives in a deluge with hurricanes; the remainder is generally spread throughout the year.
These results are very preliminary at just a year and a half into the five-year trial, so hard conclusions are inappropriate. Early on, the “best looking” plants tested at this point include the Cuphea glutinosa, Eragrostis chloromelas, Muhlenbergia Pink Flamingo, Nepeta racemosa Walker’s Low, Panicum virgatum and Rosmarinus officinalis Huntington Carpet. Plants that died the most include Chrysogonum virginianum, Penstemon barbatus, Phlox subulata, Rudbeckia maxima and Talinum Kingwood Gold.
Kirk’s early thinking is that overall the health and aesthetics of plants in the trial structures is good. There’s been limited mortality. Canopy coverage is good, but plant spacing is tighter than normal commercial practice. He’s looking to run this trial for five years and to continue trialing plants for southern green roofs in addition to testing different media and irrigation regimes.
If you’re interested in reaching out to Kirk, he can be contacted at firstname.lastname@example.org.
December 1, 2016 NewTerrain.