Rock Garden Workshop
by Mary Ellen Asmundson
Ted and Sandy Milam gave a workshop on the basics of building a rock garden to me and other interested NARGS members on August 18 at the Evergreen Arboretum and Gardens in Everett.
Sandy began the workshop with some arboretum history. The Rock Garden at the Arboretum, one of 10 themed gardens in the 3 ½ acres, was started in 2006 with funding in part from a grant from national NARGS.
Ted then gave information on construction and planting of a new rock garden using the
photo by Kendall McLean
Rock Garden at the Arboretum as his model. Ted and Jeff Gibson did the original design on a slope. They built it at a size a home gardener could do using mostly 1-2 man rocks and moving them into place with a rock dolly.
They used locally available rock “local green rock”. The rocks were buried about 30 %. Ted said the rocks are just as important as the plants in the design. He indicated that which type of rocks you use aren’t critical but selecting angular rocks which can form overhangs and outcroppings are best for creating a variety of plant habitats.
After the rocks were placed, they were covered with a foot of sharp, coarse builder’s sand, and then topped with mini shot and sharp pea gravel. Ted said it is important to inspect the texture of the builder’s sand before delivery. Using the sterile material encourages the plants to root deeply into the native soil below. After the root systems are established it shouldn’t be necessary to water the garden. No fertilizer is used in the garden, but Ted said if any fertilizer was used it would be bone meal. The garden mostly consists of neutral ph soil. A small crevasse garden was added in 2009 and Ted did use some compost mixed with the coarse sand in the new garden.
Hundreds of plants were added with bulbs and dwarf conifers mixed in. Many plants were obtained from seed exchanges and grown by Ted. Additional plants were obtained from local nurseries including Edelweiss, Mt. Tahoma Nursery, Coenosium Nursery, and Far Reaches Farm. The plantings are varied enough so that visitors can come to the garden any month of the year and find something interesting.
When Ted plants a new plant he recommends taking all the soil off the roots first by rinsing in a bucket of water. Otherwise, he says, any peat based soil will make a dry zone for the roots when planted into sand.
The remainder of the workshop was answering our numerous questions about specific plants in the garden. Conifer Chamaecyparis obtusa ‘Sheriman’ (aka‘Chairman’), Acer ‘Mikawa Yatsubusa’, and prostrate hemlock, Tsuga ‘Thorson’s Weeper’ were some of the small woody plants that we asked about. Sandy suggested using only mini conifers growing less than 1 inch per year.
Gentiana paradoxa, Endlicheranum, a hardy pelargonium from the mountains of Turkey, and Parahebe hookeriana caught our eyes as well as a bulb, Albuca shawii, from South Africa. One plant obtained from Far Reaches Farm, Niponanthemum nipponicum, shallow rooted with attractive foliage and outrageous white mum flowers, Ted deemed “a little frisky” for a small rock garden. Ted and Sandy have tried to put name tags with the plants only to have them removed by children. (One time 250 plant labels were pulled off.) Finding a way to permanently label the plants is still in the works.
We left feeling that we had learned more than we had anticipated and with confidence that each of us could succeed in building a rock garden. Sandy sold us some choice rock garden plants donated by Kayak Green and Edelweiss Nursery (proceeds going to NARGS), and we also went home with seeds and cuttings of plants in the garden.
photo by Kendall McLean