While gardening on a slope provides unique challenges, it isn’t impossible! Whether dealing with a gently sloped front yard or a steep backyard hill, you can still grow plants at home. All you have to do is learn a few tips for gardening on a slope.
I’ll share ways to prevent erosion, control water flow, and select plants that thrive on a slope. Keep reading to learn how to grow a beautiful hillside garden.
Consider the Power of Water
To prevent slope erosion, consider designing the garden to redirect water flow.
Water is one of the major causes of erosion, and it can present even bigger challenges if you’re gardening on a slope. A heavy storm can quickly dump a few inches of water and wash away the top inches of garden soil. However, designing your garden with water in mind can help prevent erosion.
Since water moves with gravity, it will want to travel down the slope. More water will increase erosion, so limiting the amount of water traveling down the slope can help prevent erosion.
Burying a drain pipe at the top of the garden will collect water above it and direct it to another area. Therefore, less water will flow into your garden. You can dig a visible trench at the top of your garden, but a buried drain pipe is more aesthetically pleasing.
Avoid Major Tillage
Reduce erosion and compaction by avoiding excessive tillage, especially on sloped terrain.
Bare soil, especially recently tilled bare soil, is extremely susceptible to erosion and compaction. Just think about how the water flowing from established lawns is clear, but water flowing from home construction sites is murky and discolored due to eroded soil.
And since erosion is a bigger problem on sloped ground than flat ground, limiting tillage on sloped gardens is especially important. Plus, if you don’t till, you won’t have to go through the hassle of moving a rototiller through a sloped garden.
Just because you shouldn’t till doesn’t mean you must deal with compacted soils. I utilized a broad fork to loosen and aerate the soil on my sloped garden plot. This increased aeration, allowing better water infiltration and improved soil health.
Be Careful When Using Machinery
Exercise caution on slopes with machinery to prevent tipping and serious injuries.
Exercise extreme caution when working on slopes using machinery like tractors and lawnmowers. These heavy pieces of equipment can easily tip and roll, leading to severe injuries.
If you’re cutting the lawn with a riding or push lawn mower, work up and down the slope rather than across it. This will prevent the likelihood that the wheels will lift and the equipment will tip over.
Avoid operating any heavy equipment on a slope that is greater than 20°.
Think About the Gradient
Steeper slopes may need retaining walls or terraces.
While there are some similarities between all sloped gardens, the slope gradient impacts gardening practices. For example, gardening on a 5° slope isn’t much different than growing plants on flat ground, but growing on a 40° gradient requires some serious modifications.
You can determine your slope’s gradient by measuring the height change over distance. Since higher slopes are more susceptible to erosion, these steep slopes may require retaining walls or terraces to hold soil in place.
Prevent erosion on steep slopes by creating terraces with solid materials like rocks or logs.
If you’re dealing with a steep slope, consider terracing. Terraces transform the single slope into a series of flat garden beds and allow you to grow without worries of erosion.
While you can create terraces with nothing but your garden’s native soil, a shovel, and some hard work, the terraces may wash away in heavy rains. Utilizing logs, rocks, concrete blocks, and other materials can help keep the terraces in place.
Use these solid materials to create vertical walls, then backfill up the slope to create a flat garden space. A taller wall will lead to a larger gardening space, but it will also increase the chances of erosion.
Choose Plants with Diverse Root Systems
Prevent erosion on slopes by planting a variety of deep-rooted shrubs and trees.
Roots help hold soil in place and prevent erosion. Therefore, aim to fill your sloped garden with diverse root systems.
Shrubs and small trees have deep root systems that help stabilize hillsides year-round. Adding a few of these larger plants throughout your sloped garden can help keep soil in place.
Along with deep-rooted plants, consider adding plants with extensive root systems. Mixing in perennial plants with annual plants will help keep the soil in place before you plant and after you harvest annuals.
Incorporate Rock Features
Use riprap to prevent erosion on sloped gardens with poor soil.
While plants help decrease erosion, they’re not the only option. Rocks protect the soil from rain and, therefore, prevent erosion. That means they’re a great option for sloped gardens, particularly in areas with poor soil.
Adding riprap, piles of larger rocks, to sloped areas is a great way to help prevent erosion.
Fill in Blank Space with Ground Covers
Choose ground covers like creeping thyme and native grasses to prevent hillside erosion effectively.
Ground covers are some of the best plants for hillside gardens. Since they blanket the ground, they do double duty to prevent erosion—the foliage protects the soil from erosive rain and wind, and the roots help hold the soil in place.
Some popular low-growing groundcover plants include creeping thyme, red clover, creeping phlox, and winter creeper. And if you don’t mind taller plants, check out native grasses like blue grama grass and little bluestem.
Work with Water
For better water drainage on slopes, align beds with the slope direction.
If you’re growing using a bed system, I find it’s best to orient beds with the slope. Part of my farm is on a plot with about a 15° slope. I’ve run the beds so they run from the top of the slope to the bottom rather than across the beds.
When heavy rains fall, as they often do in East Tennessee, water runs off the beds and into the pathways. It then travels down the sloped pathways until it flows out the bottom of the garden.
If you run beds across the slope, heavy rainfall may lead the beds to erode as the water moves with gravity. I recommend building terraces if you want to orient beds across the slope.
Leave Plant Roots in the Ground
Avoid soil disturbance and erosion by cutting plants at the soil’s surface and leaving the roots in place.
When the end of the growing season arrives, you may be tempted to yank annual plants like tomatoes and zinnias out of the ground. But wait a minute! Pulling the entire plant will remove the plant’s roots, disturb the soil, and increase the likelihood of erosion.
A better option is to cut the plant off at the soil surface, leaving the roots in the ground. The roots will continue to hold the soil in place and feed soil microorganisms.
If you’re not planning on planting another plant in the same area anytime soon, you can leave entire plants in the ground. For example, leave winter-killed annuals in the garden over the winter and clean up the plants when spring arrives.
Keep the Soil Covered
Enhance soil health and prevent erosion by planting winter cover crops or using mulch.
The first frost and cold temperatures often kill plants and prompt garden cleanup. While you can leave these dead plants in your garden, you may wish to tidy things up and remove them. If you choose this route, don’t leave the soil bare throughout the winter!
If you pull summer crops like tomatoes, cucumbers, zinnias, and sunflowers in the early fall, you still have time to plant a fall or winter cover crop. This crop will enrich soil health, prevent erosion, and help keep nutrients in place.
Some popular winter cover crops include winter rye, crimson clover, Austrian winter pea, and oats. And remember, you don’t have to choose just one cover crop—mixing and matching a few plants can create a diverse above-ground and below-ground ecosystem.
If you missed the window for planting winter cover crops, don’t leave your soil bare over winter. Instead, cover it with a layer of leaves, straw, or wood chips. And if you want to avoid the work of spreading mulch, you can pull a silage tarp over the soil to protect it throughout the winter.
Install stairs on steep slopes for easy access and erosion prevention.
If your backyard is a steep slope, consider adding stairs to help you travel up and down your garden. Not only will stairs make it easy to walk up and down, but they can also help prevent erosion.
Adding stairs can be as simple as inserting two stakes into the ground, placing a log behind the stakes, and backfilling the area with soil. You can also dig out the slope and stack large rocks to create a staircase.
If you’re dealing with a steep slope and aren’t confident in your understanding of erosion and construction, consider contacting a landscaping design company for a consultation.
Utilize Anchor Plants
Prevent erosion on slopes by incorporating perennial anchor plants alongside annuals in your garden.
Whether you’re planting an ornamental or edible garden, don’t just clear the entire slope and plant annuals. Instead, utilize perennial plants to help anchor the soil in place. Scattering these plants throughout the garden can help prevent erosion while also leaving room for annual plants.
Some anchor plants that work well on sunny slopes include purple coneflower, black-eyed Susan, rosemary, and sage. These perennials remain year to year and also require little maintenance.
If you’re growing on a shady hillside, consider perennial plants like astilbe, hosta, and hellebore.
Think About Plant Maintenance
Opt for low-maintenance native plants on slopes for minimal upkeep and thriving gardens.
Remember, you not only have to plant your plants, but you also have to maintain them! If crawling up and down a steep hillside doesn’t sound like your idea of a good time, plant low-maintenance plants. Also, perennial plants require less work than annuals since you plant them once, and they live for years.
Native plants are great low-maintenance options since they’re adapted to live in your area without human care. Remember that native plants vary between locations, so you’ll want to take some time to investigate the plants native to your area.
With that said, species of coneflower, goldenrod, and milkweed are native to much of the United States. These plants will naturally die back in the fall and remerge each spring. They can tolerate drought and grow with little fertilizer, meaning you won’t have to put in much work to help them thrive.
Avoid Invasive Plants
Choose native plants to stabilize slopes, avoiding invasive species that can overpower the native vegetation.
When you search for plants to help stabilize slopes, you’ll likely encounter some invasive plants. And while it’s true that many of these plants can help hold soil in place, they’ll also quickly overwhelm native vegetation and other plants.
Just look at the kudzu covering hills in the southeast or Japanese barberry in the midwest to see what I’m talking about. Some common invasive plants to avoid include Japanese honeysuckle, autumn olive, kudzu, privet, Japanese barberry, buckthorn, English ivy, and common periwinkle.
Instead, opt for native plants. These plants will still hold the soil in place while also providing food for wildlife and allowing other plants to grow.
Add plants to slopes with retaining walls or terracing by using containers for easy care.
If you have a slope that’s held in place with a retaining wall, stairs, or stone terracing, you can still add plants to the area. Rather than growing in the ground, you can plant in containers.
Pick a few pretty pots, fill them with potting soil, and plant some herbs or flowers. Just remember that you need to water the plants, so place them where you can access them.
Consider Slope Direction
Consider sun exposure on slopes based on their direction—south-facing slopes receive more sunlight.
While flat, open areas will receive full sun, the direction a slope faces greatly impacts sun exposure. In the United States, a south-facing slope receives full sun, but a north-facing slope receives less sun.
Therefore, look at the amount of light the slope receives before selecting plants. It’s best to check at different times of the day so you have a good sense of when and how long the sun will hit the area you’re working with.
Prevent runoff and erosion on slopes by installing ponds with plastic liners or natural holes.
If you don’t want the water that runs off your slope to puddle at the bottom of the hill, create a few ponds. These will catch water in a designated area, preventing erosion and mud.
Pre-formed plastic pond liners are easy ways to create ponds. You can also dig a large hole if you live in an area with heavy clay soil.
Fill the ponds with aquatic plants like lilies, lettuce, and pickerelweed for extra beauty. Another option is to create a bog and add plants like false blue indigo, cardinal flower, and pitcher plants.
Cover bare areas with mulch in winter to prevent erosion and conserve moisture.
If you’re growing annual plants, you’ll have bare areas in the winter. Rather than letting these areas sit empty as the weather cools, apply some mulch to cover the soil. This will prevent rain from splashing the soil and help slow the water flow.
Wood chips, leaves, and straw all work well as mulch. If you expect an area to remain empty for over a year, add a layer of pebbles to help keep the soil in place.
You can also mulch around growing plants to help keep soil in place and conserve moisture. The mulch will also prevent weed growth and limit your time pulling weeds.
Now that you know a few hill-management tips to assist with your gardening, you’re ready to tackle the challenges of growing on sloped land. Remember to cover the soil, pay attention to water flow, and choose low-maintenance plants.