Just the other day, I found notes that I put together for an informal talk about gardening on steep slopes. We, here in the Pacific Northwest, have plenty of gardening opportunities (and challenges) to garden in areas where beach lines, drainages, rivers, or slumps have created a difficult garden topography. Even though I am now gardening on a property that has plenty of flat land (which harbors plenty of issues in itself), I did spend considerable time working on a very steep ridge…so here are some suggestions for not going down a slippery slope! It’s harder to work—but the rewards can be great, especially in the DRAMA that is inherently contained in altitude changes.
One of the biggest considerations is accessibility. I’m not talking about making your mountain-goat garden wheel-chair accessible. I’m simply talking about getting around and being able to do the maintenance in the garden. Be sure to make paths, especially “main” or oft used paths as comfortable and accessible as possible. Use switchbacks to minimize altitude gain. they may be longer, but are definitely easier on the knees. This may not always be possible, but it’s a good aspiration. Another thing to think about is break up steps into small sections. Rather than forty steps all at one time (remember this isn’t a pilgrimage route) , split up the steps into small sections. Five flights of eight steps each are A LOT EASIER!
As for ANY garden, make the major paths much, much wider than you think you need. This is such a difficult directive. EVERY garden writer and designer says it…but it takes several years of gardening to finally BELIEVE it. Oh gosh, you think, I don’t want to WASTE all that space in paths. After all, I could plant so many more plants along those side spaces. Ah, therein lies the problem. Those edge plants will grow…and likely flop all over that path. What WAS a three foot path, after being encroached from left and right by six inches is now an two foot path…and NEXT year, those plants will be encroaching a foot on each side…and you are left with a goat path at best. Trust me on this.
Remember maintenance! It IS best if you can actually “get there from here!” Wherever possible, leave wheelbarrow accessibility, unless, of course, you really LIKE hauling stuff up and down in buckets. If you have extremely steep areas with steps, see if you can weave a side path that won’t be too obvious for a wheeled conveyances. One of my favorite tricks is to embed some “stepping” stones in very steep hills among your plants, so that you have little places to stand on a slope when weeding and don’t slip and slide or mangle your plants during maintenance…you can just stand on your hidden platforms..
When cutting paths into side of hills, remember that the soil on the up side of the path will slip into the path and the soil on the down side of the path will slide away. Reinforce with rock or barriers to minimize path maintenance. Don’t clear steep slope areas. It’s not legal, for one. We inter-planted garden plants (shrubs and ground covers) with natives…or even invasives (We temporarily left blackberries in many areas, for example).…until the garden plants were robust enough to hold the bank. Agricultural Extension programs have information about good slope maintenance plants. You want to have plants that create robust and deep root systems to stabilize soil movement and run-off. Walk around in your own immediate area. Look at the native vegetation on the steep areas. Note what seems to be holding on at seemingly untenable angles. Get those plants; that’s always a good place to start.
In our Pacific Northwest climate, try not to use slippery materials in especially steep areas. Particularly in locations where you need to take a step DOWN. Avoid making anyone have to land onto a slick-when-wet surface or rock. At Ridge Garden, we had to change out many of our beautiful blue stones on our paths to the safety of smooth gravel surfaces, because perilous descents. They were beautiful paths, but way too hazardous. Even with the best of planning, we sometimes had to spread sand as temporary measure to “roughen up” some rock surfaces in wet weather. On our many railroad tie steps, we nailed down 3-tab roofing material (without the tabs) to add more traction. I liked to use dark colors that didn’t show very much, but contrasting colors might be interesting as well.
One last practical matter: Watering on a slope is very difficult. Grow as many plants that don’t need watering and don’t plan on a drip watering system. The bottom will be well watered, but the upper regions will not be. Sprinklers, especially small area emitters will work better for distributing water and minimizing runoff. Do as many lateral lines as possible, to prevent upper dry areas. Water does have a tendency to head downhill!
Working on a “difficult” sloped plot, gives you great opportunities for showing off plants. Put downward facing flowers on the upslope so you can look into their faces. Other plants look great from above, put them on the downslope. Many plants thrive when their roots are anchored between rocks. Search out those plants and use them—rock gardeners will drool. Drama is much easier on a slope. Switchbacks provide lots of peek-a-boo sites where you can surprise your garden guest with something wonderful and unexpected. Our elevation from street to house at Ridge Garden was the equivalent of eight or nine flights of stairs. We put little patios with different themes and styles as well as and sculptures or features to surprise and entertain the garden guest as they ambled up the hill. A slope provides lots of “hidden” areas that invite exploration and prevent visitors from seeing the whole garden all at once. It’s a gift, optimize it!