Before you develop a landscape plan or buy the first plant, analyze your site so that you can match your garden goals and plant characteristics to your specific environment. Important site characteristics include sun, shade, moisture, and wind patterns. Identify problem areas such as erosion, standing water, invasive plants, and weedy or overgrown areas. Locate focal points to highlight or preserve. These could be a wildflower meadow, rhododendron thicket, specimen tree, nice rock formation, or even a dry streambed.
How steep is it?
Site analysis takes on special importance when your property is on a slope. Take time to calculate the steepness of your slope: Rise ÷ Run = Slope %. You cannot push a garden cart or ride a lawnmower on any slope over 40% steep. If your slope is over 55% steep, you cannot walk up it without foot- and handholds. The steepness of your slope becomes a critical factor for what you choose to plant and how you maintain it. Note if your property has deep ravines. Because cold air settles in low-lying areas, the bottom of your slope may not be the best place for marginally hardy plants or early-blooming azaleas.
What should you look for? Is an area full sun or deep shade? How many hours of direct sun does it get in a day? Is the sunlight gentle, morning sun, or hot, baking, afternoon sun? How do the light patterns change with the seasons? At what time of day is your garden shadowed by a permanent structure like your house?
When monitoring sun and shade patterns, note how the mountain slopes themselves may cast deep and long shadows. Vegetable gardens, roses, and sun-loving perennials need about six hours of direct sunlight a day to thrive.
Look at soil moisture levels and stormwater drainage. Steep slopes can be very dry because rainwater runs off quickly, rather than being absorbed into the soil. You may need to consider drip irrigation for plants on steep slopes. You may have areas of your property that stay very moist or have standing water. These may be candidates for rain gardens. And if you have erosion problems, decide how you’ll resolve those before you plant. While serious erosion problems may require stormwater management solutions, choosing the right plants to anchor the soil might fix minor erosion.
Our acid mountain soils usually best suit acid-loving plants—azaleas, rhododendron, and conifers. And mountain soils are often notoriously low in phosphorus. Do soil tests around different areas of your property to determine pH and mineral content. You’ll find soil test kits with “how to” directions at the Buncombe County Extension Office. The results will help you decide what fertilizers and other amendments to use.
The lay of the land
Analyze your visual perspective. If you’re looking up the slope, what will you see? Is it a view of plain tree trunks or leggy flower stems? If so, think about hiding unsightly views by layering your plants. Place the tallest plants toward the top of the slope, then step down to mid-sized, bushier plants, and finally put the shortest plants at the bottom of the slope closest to you. The same concept works in reverse, if you’re looking down the slope. Put the short plants at your feet and the tallest plants farthest away. The low-growing plants help extend your field of vision and won’t make you feel closed in when you walk near the sloping hillside. The tall plants create a backdrop to anchor the garden, much like the walls of a room. An integrated mix of plants by size, color, and shape also helps camouflage and add to the interest of a steep slope.
Article written by Beth Leonard, Extension Master Gardener Volunteer.