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Gardening Tips - Hillside Gardening
Many of us in Marin are challenged by our hills. How do we get the water to penetrate on a steep slope? How can we prevent erosion? How do we manage rocky soil? And what about the wind? Is your hill too steep to walk on?
Hillsides are best adapted to informal design. It’s such fun to shop for plants that look good in the nursery, but quite disappointing when they fail once in the garden. A word to the wise: Prepare!
Gardeners would do well to perform an initial site analysis addressing all the conditions for their site. Microclimate can be determined by using the Sunset zone finder. If your garden is at the top of the hill or the very bottom you will most likely have frost, so select plants thoughtfully. A simple soil analysis kit purchased at a local nursery can determine the acidity or alkalinity of the soil. For greater accuracy soil samples can be sent to a soils laboratory. If your hillside has many conifers and oaks the soil is almost certainly acidic. Most plantings prefer slightly acidic pH, below 7.0.
Most Marin soils are clay, which has the advantage of holding water and the disadvantage of being tricky for roots to navigate, not to mention our shovels. Trees and shrubs are the “bones” of a garden and can be useful in diminishing the effects of wind and further erosion. California native plants are a wise choice. They prefer native soils and anchor well to prevent erosion. Adding groundcovers and perennials can complete the picture, adding color, texture and interest.
On clayey soils, soil amendments improve the soil aggregation, increase porosity and permeability, and improve aeration, drainage, and rooting depth. When planting incorporate ¼ amendment to ¾ native soil. Use even less for native plants. Dig a hole 12 inches deep and fill with water. If it drains in an hour drainage is good enough.
A well-designed hillside can do much to eliminate the need for costly retaining walls. Whenever possible add stairways or stepping-stones to help navigate the slope for tending to pruning and weeding. The less you walk on your soil the less compaction and slippage you’ll create.
Use drip irrigation and place emitters strategically at each plant. Avoid spraying as winds and evaporation diminish penetration. Use an irrigation controller and set to apply water in short cycles to prevent runoff. Let water soak in before second cycle. Even better, choose drought tolerant plants which abound and thrive in our Mediterranean climate.
Now you’re all set to start shopping! Here are just a few of the many useful websites to browse before you head out the door that allow you to select by category, color, habitat and more.
Annie’s Annuals
California Flora Nursery
Cottage Gardens of Petaluma
San Marcos Growers
Yerba Buena Nursery
Written by Mary Warner, Marin Master Gardener