By Charlotte Torgovitsky

In 2012, the Marin Chapter of CNPS created a native plant demonstration garden at Green Point Nursery.  This slide show takes you through the process of creating this garden. (Note that this demonstration garden no longer exists since the Chapter no longer has the use of space at Green Point Nursery.)

This The garden had to be created from scratch on bare flat ground.  To create aesthetic interest and better drainage, a berm was constructed to which large rocks were added.  Although most home gardens will use existing soil and terrain rather than a newly constructed berm, the planning steps and construction sequence that we used for this demonstration garden are similar to those used in creating a home garden.

Here’s the site – bare bones: full sun, heavily compacted fill soil, and right next to the road. When faced with such garden unfriendly circumstances, the best solution is to “Berm Up”. By building a mound of soil you can create an ideal situation to get California native plants established.

The garden design was drawn up by Jeanne Lau Landscape Architecture, and can be referred to for all the details regarding contouring, boulder placements and soil quantities. The berm is about 45 feet long by 14 feet wide, encompassing about 1,700 square feet; the outline of the berm was drawn on the ground to give us a perimeter to work within. We used a simplified approach to sheet mulching by laying down sheets of cardboard within the drawn-out perimeters; smothering any remaining weeds, and setting up better conditions for any soil biota present. Gopher activity was evident in the out-lying areas, so as a precaution we also laid down galvanized chicken wire. Earth staples help hold these layers in place within the perimeter, and we’ll rely on stone edging to hold the outside edges.

We started the berm building process with a drystack urbanite wall; 18 inches high by 36 ½ feet long, and set 4 feet back from the fence. A concrete contractor was more than happy to deliver all the broken out pieces of an old driveway. He helped us out by breaking out uniform pieces of concrete to the extent possible. The contractor also supplied the first foot of clean fill; all recycled and reused materials, and all delivered to the site. We all save on this kind of recycling; the contractor on dump fees, homeowners and garden designers on materials fees, and the planet on so many other levels. Another great benefit of drystack walls are all the hiding places that are created for insects and other small animals.

Marin Landscape Materials delivered 16 cubic yards of soil to build up the berm. It is important to get a really basic soil for a native planting; Tony at Marin Landscape worked with us on this special order of sandy loam brought in from Napa County. Avoid using soils mixed for vegetables or ornamentals; these standard soil mixes often incorporate animal manures and wood shavings or sawdust. Most natives don’t want a lot of nitrogen in the soil.

Boulders are next in the garden design process; we hand selected large basalt boulders at W. Johnson Stoneyard in Santa Rosa. They deliver and bring a bobcat to help place the stones exactly where and how they are wanted. Stones, cobbles and boulders all help create structure, focal points and interest in a garden design; plus they create a heat sink, help conserve moisture, and provide cool root runs for plants growing close by.

Placing the boulders just so really adds interest to the design. For a natural look dig in about one-third of the bulk of the boulder or cobble edging. We found one large boulder that had a natural cavity which we knew would make a great birdbath!

Here we are digging in boulders and making decisions about exactly how they should be placed. Bill Johnson from the stoneyard waits patiently on his bobcat until we decide.

Boulders are in place, and now we’re ready to add amendments to the soil. We had 5 cubic yards of All-Green compost delivered to provide humus to the natives that will appreciate more organic matter in the soil, and 3 cubic yards of 3/8 inch lava rock for the natives that will want slightly drier conditions and especially good drainage. The All-Green compost contains no animal manures, and is available from Grab n’ Grow in Santa Rosa.

Our design is starting to take shape! We’ve dug in the compost, and are defining the edges with a row of ‘head-sized’ stones. We set up a nesting box for Tree Swallows; they moved in right away and successfully raised a brood.

We’ve made some decisions about the plants to include in the garden.

Digging them in, still in their pots, helps us to decide on exact placement and groupings. The lava rock will be dug in as needed.

Most plants are in the ground, and Sonoma fieldstone edging is complete.

Two different irrigation systems were installed by The Urban Farmer Store on the big berm. Specimen shrubs planted toward the top are watered by individual emitters inserted into the solid black line. At the base of the berm an in-line drip system irrigates smaller perennials and groundcovers. North Marin Water District generously provided the funding for the irrigation systems and a weather sensitive timer.

The brown line has in-line emitters spaced every twelve inches. The tubing is held in place with earth staples.

Once all the plants are in the ground and irrigation systems all laid out and functioning, we applied about an inch of mulch to cover the soil. We used ‘early-screened mulch’ made by Sonoma Compost which has enough rough materials to hold it in place on slopes and in windy areas.

We selected plants appropriate for a hot, dry site; Salvias, California Fuschias, Monkeyflowers, Buckwheats and Lizard Tail, to name just a few. We filled in with a variety of annual wildflowers, such as Clarkias, Poppies and Tarweeds. All the plants in the garden were labeled with botanical and common names.

Elegant Madia, a late-blooming tarweed, really took off!

Lizard Tail and white and yellow Hemizonias all thrive in this environment.

Within six months most plants are well established.

The garden needs minimal maintenance during the year; we weed late in the summer and fall, and cut shrubs and perennials back early in the spring.