Gardening, like life, offers its ups and downs, and hillside gardening is definitely one of its more challenging endeavors. Think of it as a learning opportunity that hones your ingenuity, design skills and appreciation for the resilience of hardy plants.
Slopes are prone to water loss and erosion, but with careful plant selection and a little earth sculpting, you can create a personalized landscape, reduce runoff and provide wildlife habitat, says Heather Voss, of Heather Gardens in Medford. Re-planting grassy hills with more diversity also helps reduce fire danger and the need for weed abatement. If your garden area is flat, creating a berm or mound provides visual contrast and creates a fun, new challenge for you.
Choose perennials for the staying power that hillside gardening requires, and for low-maintenance landscaping.
Promote water retention through terracing or digging small trenches, following land contours.
Install drip lines or make a simple drip system from an older hose by puncturing holes at regular intervals and capping the end. If you can’t terrace or use drip, water lightly for about 5 minutes several times per day, says Toni DeVenney of Valley View Nursery in Ashland and Medford.
Amend soil with compost to facilitate water retention, help plants thrive in the challenging hillside environment and nurture your garden without chemical fertilizers.
Use mulch to protect against erosion and water loss, and to control weeds organically.
Begin planting from the top of the hill down, to avoid damaging your work. Place more drought-tolerant plants at the top of hill since water will flow down and collect at the base level.
Use well-placed rocks to support new plantings from below and provide visual accents. Rocks retain heat so locate them carefully on exposed slopes.
Dig terraced steps into wide hills to create pleasant walking paths and protect developing root systems.
To start off right, assess sun and terrain first. Exposed south-facing slopes receive and reflect the most sun, so you’ll need drought- and heat-tolerant plants here. North-facing or well-shaded southern slopes call for part-sun and shade varieties that like moist soil. Gardens on slopes with greater than 20 or 30 percent incline are difficult to establish as is, but you’ll get great results if you terrace. Natural materials such as jute netting or a straw blanket can also provide the soil stability needed for success.
Observing the flow of water and wildlife is also important. Water patterns point out drainage and areas prone to damage. “Watch where deer and animal paths are and use them to establish terraces. Don’t plant in the middle of them; this would cause erosion,” says Voss. It is also important to keep frost-sensitive plants above the bottom of the slope where cold air drainage accumulates.
When adding each plant, dig a flat area around the center of the planting hole, then dig an inward slope with a bowl-shaped area in the middle. Locate the plants in the middle of the bowl. This strategy captures the most water possible, increasing your success rate.
Select perennials with a larger root system to hold the soil, says Toni DeVenney, of Valley View Nursery in Ashland and Medford. As trees, shrubs and perennials become established, work in shade-tolerant plants under their canopies. If you include ground covers, shrubs and trees, this multi-story buffer will decrease the impact of raindrops on the soil. Mix in herbs and fruit trees for culinary delight and beauty from flowers and visiting butterflies.
For hot, dry slopes Voss recommends lavender, rosemary, ornamental grasses, rock rose, cotoneaster, strawberry tree, manzanita, butterfly bush, Oregon grape, mock orange and elderberry. If terraces are present, creeping rosemary will cascade beautifully over the contours. DeVenney likes Point Reyes ceanothus, chamomile, fescue and ice plant. On wet, cooler hillsides choose among fern, flowering quince, willow, spirea, red or yellow dogwood or Japanese birch.
Voss advises caution when selecting ground covers. “I would dissuade using St. John’s wort and vinca major because they are so invasive. They are good plants but they do not contain themselves to the hillside.” DeVenney would consider these only in very large areas.
Hillside gardens require extra TLC the first year or so, with basic needs after that. With these tips in mind, your initial efforts will reward you with great views, lower maintenance and ongoing room for creativity. Start planning now for a head start on some invigorating spring planting!