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Beech Knoll: Renovation Project, Fall 2022

January 4, 2023


Why not seek to explore more than the main path? Discover nature and immerse yourself in the presence of trees, Mother Nature’s cathedral.– MaryAnn Thesing

Working with Nature

In 2021, Landscape Architecture Intern, Yuhan Ji, was tasked with restructuring key views in and around Layer Rhododendron Garden, including Beech Knoll, here at Holden Arboretum. The goal is to give visitors an integrated experience as they explore Rhododendrons up close. Expansive sight lines from intimate spaces help to draw the visitor along garden beds, aiding in exploring hidden spaces. In May of 2022, I was hired as Horticulturist to care for the 25-acre Layer Rhododendron Garden – since then, Beech Knoll has been a high priority for weed control by hand weeding & cardboarding, followed by mulching with Pine Bark Mulch Fines. Cardboard is a great weed suppressant, and the pine fines will, eventually, work their way into the soil, improving soil structure and allowing more oxygen and water to reach the roots. After working in the space, I was inspired to eliminate the grass on the western side of Beech Knoll in areas where it is struggling in the deep shade. After some research and many discussions with Annie Rzepka on what the best substitute may be, we have come up with several sedge options: Carex pensylvanica, Pennsylvania sedge, and Carex platyphylla, silver sedge, will be used as primary grass substitutes.

Carex pensylvanica
Carex platyphylla

The great thing about these sedges is that they offer the perfect native lawn substitute, not to mention that they are host plants for butterfly and moth caterpillars! Overall, it’s a win/win. Please note, if you are considering a lawn substitute similar to Beech Knoll, sedges do not do well with heavy foot traffic! As a result, we will provide an inviting foot path for visitors to enjoy.

Options for killing the existing grass:

  1. Weed whipping the grass low to ground level to weaken the roots. In Fall, plan on letting the leaves lie on the grass and chop them up in Spring by mowing. The goal is to get a good foundation with naturally amended soil for seeding in the sedge OR 2.
  2. Remove small areas of grass by hand and begin planting those areas, one by one, OR 3.
  3. Using Rhinanthus minor, yellow rattle, an annual plant that is parasitic to grass. The seeds must be sown in fall due to the need for scarification. This species is a sun-lover so a test area would be necessary so that we can judge if this is the right thing to do. Research is ongoing on whether it will be detrimental to sedge, OR 4.
  4. Glyphosate, AKA Round-up is an option, but my preference is to move forward in a way that is less harmful to the earth – so, for now, this procedure is off the table

The plan is to start in a small area on the south side of Beech Knoll where there are 3 benches. A narrow path will lead from the main trail to the seating area, where you will be surrounded with a lush forest floor. Daffodils will awaken in spring, as a reminder that warmer weather is on its way.   In and amongst the new plantings, Phlox divaricata will add to the softness of the surrounding area.

Phlox divaricata

Stay tuned for changes here on Beech Knoll!

MaryAnn Thesing

MaryAnn Thesing


MaryAnn Thesing joined Holden Arboretum in May, 2022 as Horticulturist for “Old” Layer Rhododendron Garden, which includes the Murch Canopy Walk. MaryAnn has over 7 years’ experience as a Garden Designer/Installer & Garden Coach and is a Japanese Maple & Bonsai enthusiast, owner & caretaker of The Japanese Maple Garden in Euclid, OH for 16 years.

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