Feature Article Creating a Scree Garden By Victor Piatt, Head Rock Monkey, Mt. Cuba Center

want you to create an outcrop/ few moments on what just happened, “I scree garden in this area,” he said. and how I was the chosen one for A quick scan of the immediate sur- this project. Let’s see...I am the rock roundings; suspicion confirmed he gardener at MCC and do consider was speaking to me! An avid plant myself to be a rock monkey, but collector, Rick Lewandowski, former neither made me an expert at rock

Director of Mt. Cuba Center (MCC), garden design. I also concluded that, at Piatt Victor wanted to create a garden area to grow some point in my future employment,

and interpret native plants that are in- I’d get my comeuppance for this with photo © digenous to the granitic and dolomitic Jerry and Pete, for my new status as Aerial shot of scree garden—walking outcrops he explored in the Piedmont boss. If I were to have anyone’s help path bordering outcrop, arching formation to right, and scree planting regions of Georgia and Alabama; with a project like this, these guys bed. (February, 2012) flat-rock habitats as they are some- would be the ones—muscles and a times called. “Well, the Rock Wall is propensity to not take “No” for an to blast through a massive outcrop of right there, what’s wrong with that?” answer. With churning doubt and rock to lay the driveway, resulting in I chirped, while pointing across the anxiety, I accepted Rick’s request. the creation of the Rock Wall to the Main Drive. He lamented–it was the west. Perhaps there was some remnant logical location, but he had a grander of that outcrop just below the surface vision...as I would soon discover. on the east side of the driveway? Late Rick proceeded to express his September, 2007, Jerry was on the vision of this garden and provided backhoe, excavating, with me, fingers a few guidelines: large rocks would crossed, waiting, and hoping that be needed to avoid having to use any contours don’t lie. As Jerry unearthed mortar, their weight would keep them the southern end of this site, the in place, and the bulk of each rock hidden geology began to reveal itself. would be buried; the soil in the area photo © Mt. Cuba Center Ultimately, an exposure of 40' in should be removed as much as possible 1993 View north along Main Drive; length was unearthed. This outcrop and landscape fabric should be laid as Rock Wall on left; on right, future site of would become the backbone of the an additional precaution to prevent, scree garden. scree garden. or slow, the plants from rooting into The Site From a 2012 aerial photograph, the richer soil; and lastly, this area should The narrow strip of land that would outcrop’s outline can be seen and is be austere, neither rock nor plant become the Scree Garden runs in a reminiscent of a raised eyebrow. The competing against each other. Hmm, north-south parallel along the Main outcrop slopes downward from west the Rock Wall would not suffice. Drive of MCC and is directly across to east, while stretching northward I had no idea what to do or how from the Rock Wall garden. This and gently spilling into grade, to even begin this project. By this area’s landscape consisted of mature ultimately submerging underground time, two staff members, who Rick princess trees (Paulownia tomentosa) again. With the overall perimeter of had asked to join us for the discussion, and Chinese juniper (Juniperus the garden established, we began appeared: Jerry Sterndale and Pete chinensis), probably forty years old. contour grading on the eastern edge, Shotzberger. At this point, neither of These were removed, revealing the and with broom in hand, swept loose them were aware that they were being long unseen stretch of contoured soil and debris off of the outcrop. drafted into this project. These guys ground that gently rose to about 4' This is when it got exciting for me; have tens of years of seniority and high, then dropped off in a steep this rock formation was mesmerizing! experience over me. Rick shared with slope. The contour suggested, and There were, seemingly, endless them what he had told me. Then his we thoroughly hoped, that under all folds in the formation, each one final words to me, and in earshot of that soil there might be a formation of more intricate than the next. Rock Jerry and Pete, “You’re in charge.” rock. This area of the Main Drive is monkey—oh yeah, geologist—uh, What? Ok, then...I reflected for a where workers, in the early 1930s, had nope! I inquired to geologist Sandy

Vol. 28, No. 4 Hardy Plant Society/Mid-Atlantic Group 3 Schenck of the Delaware Geological to use stone/rock in such a visual Survey, University of Delaware, and context, it should be indigenous to learned that the formations of rock your locale. And don’t scratch them at Mt. Cuba Center are comprised of up—at least the part you’re going to Wissahickon gneisses that contain be viewing. That issue was cleverly veins of quartz pods and numerous solved by Jerry, who simply sleeved granitic pegmatites. I had seen similar the chain in an old canvas wrapped folding patterns in the Rock Wall fire hose. I handpicked each rock, Piatt Victor over my 20 some years of caring for scrutinizing the details of each one to it; confirmation enough for me that, determine the best “face” and profile, photo © before the driveway was installed, the remembering that the majority of Pete and Jerry positioning large rocks. (January, 2008) Rock Wall and this newly unearthed each rock would not be visible. Once formation were connected. This belief I determined the profile, I struck a would be my overarching guide in chalk line, and anything below this the design and installation of this line would disappear below grade— garden—to visually unite these areas. essentially creating the flat rock design Rick had envisioned. Crusher run was The Scree Planting Bed used to set the height of some of the With the contour grading mostly rocks and to mitigate the removal of complete, and the outcrop cleaned soil. Wanting this garden to present as Piatt Victor off, attention turned to the details natural as possible, I took great pains photo © of what would be the scree planting to mate the rocks and align the fold Mating rocks to determine area of rock bed. The borders of this planting bed orientations with the newly exposed to be buried. (January, 2008) would be defined to the east, in part, outcrop. This placement aspect of by the newly unearthed rock outcrop, the design process was undoubtedly and to the west, entirely by the thick the most time consuming and got granite curbing installed in 2006. me many an eye-roll from Jerry. The This is the area where the large rock finished garden contained54 “hand- elements, suggested by Rick, come placed” rocks, and I laid out a gravel into the design. They would function path along the eastern border for as a visual interest and slow the flow maintenance and visitor access. The Victor Piatt Victor of water during heavy rains, mitigate overall design is of a half-ellipse, 130' some of the soil being removed, long and at the widest point 25'. photo © complete the eastern border where the Chalk line denoting area that will be outcrop submerged underground, and Planting Medium buried. (January, 2008) establish a north and south border. Quite satisfied with the placement This defined area would serve as the of each rock and with the layer of featured planting site for those granitic crusher run installed, it was time to and dolomitic outcrop plants from focus on the planting medium. I was Rick’s collection trips. To simulate completely clueless as to what a scree the lean soils of these outcrops, the medium was, let alone where to get it. existing soil was removed as much Rick postulated that, basically, we had as possible, and, as added insurance, created a green roof—it just happened Victor Piatt Victor landscape fabric was laid to prevent to be on the ground. He suggested or slow the plants from rooting into that we use an extensive green roof photo © what richer soil remained. A growing planting medium. I contacted Laurel Water line laid. (January, 2008) medium would be needed, but at Valley Soils (laurelvalleysoils.com) this point we did not know what that to inquire about such a product. They would be. Soil removed. Fabric laid. It suggested that I use their 80/20 mix was time to place the rocks. for this application. This mixture is 80% mineral, comprised of expanded Rock Elements shale and calcine clay, and 20% All of the large rocks were found organic matter. In this instance, it was on the property and required a mushroom compost. It took seven one- backhoe and a heavy chain to move ton bags to complete the scree planting Piatt Victor them—oh, and one large forklift.

area. Let the planting begin! photo © I am of the ilk that, if you are going Scree medium being laid. (February, 2008) 4 Hardy Plant Society/Mid-Atlantic Group July 2014 Victor Piatt Victor Mt. Cuba Center Victor Piatt Victor photo © photo © photo © Jerry and I temporarily placing rock. Completed garden. (March, 2008) Scree garden. (June, 2009) (March, 2008) Within six months’ time, we created this flat rock habitat garden. By using the elements of the indigenous rock and the wild collected plants, I achieved my desire to unite this garden with the Rock Wall garden. I’ve provided the names and photos of Victor Piatt Victor Victor Piatt Victor some of my favorite scree plants—I didn’t forget you plant photo © photo © people! Largest rock element being placed— Scree bed planting. (August, 2009) about 6,000 pounds. (March, 2008) Victor Piatt is the Rock Outcrop & Scree Gardens horticulturist at Mt. Cuba Center in Hockessin, DE, where he has been blissfully employed for 22 years. He held the positions of Cut Flower gardener and Plant Evaluation horticulturist for eight years, respectively. He is a 1992 graduate of Longwood Gardens’ Professional Gardener Program. Victor Piatt Victor Victor Piatt Victor Ed Note: For a full-color version of this article, go to the HPS/MAG web site, www.hardyplant.org. photo © photo © Rock in place, 9 x 4 x 2½'. (March, 2008) Scree garden. (October, 2009) Victor Piatt's Favorite Scree Plants Victor Piatt Victor Victor Piatt Victor Victor Piatt Victor photo © photo © photo ©Victor Piatt photo ©Victor photo ©Victor Piatt photo ©Victor Lithospermum canescens photo © Bigelowia nuttallii Delphinium Silene virginica Xerophyllum alabamicum asphodeloides

Vol. 28, No. 4 Hardy Plant Society/Mid-Atlantic Group 5