If you’ve always admired the gentle slope of your landscape and dreamt of a lush green paradise, you’re not alone. However, turning bare slopes into thriving grassy areas can be a challenge. In this user-friendly guide, we’ll walk you through the process of planting grass seeds on slopes, so you can transform your dream of a vibrant green lawn into reality.

Understanding Slopes

Before we get into the nitty-gritty of planting, let’s grasp what a ‘slope’ really is. Essentially, it’s how steep or flat the land is, and it plays a vital role in understanding how water flows across your property.

In simple terms, slope measures how much the ground rises or falls over a specific distance and is often expressed as a percentage. For instance, a 12% slope means the ground rises 12 feet over a horizontal span of 100 feet.

Why Slope Matters

Understanding slope is crucial for several reasons when it comes to planting and maintaining your lawn:

Safe Slope Limits: Some experts recommend working with slopes no steeper than 15% to ensure manageable landscaping. Others advise keeping grass slopes under 20%.

Erosion Prevention: Planting grass seeds on slopes greater than 15% helps prevent soil erosion, ensuring your grass stays in place even on moderately steep slopes.

Safety During Mowing: Steep slopes can pose safety risks when mowing with walk-behind or ride-on mowers. They can be slippery for walk-behind mowers, and ride-on mowers may tip over.

When the Slope Is Too Steep

If your slope seems too challenging to maintain, don’t worry—there are alternative landscaping options. Typically, slopes are suited for low-profile plants, those growing less than 4 to 5 feet tall when fully mature. For a picturesque view from the base of the slope, consider terracing it using

stones, timber, or retaining walls spaced horizontally every 3 to 4 feet. Don’t worry about uniformity; terraces can be round or flowing. Be sure to add plants to the cascading sections.

Choose plants with robust, deep roots that help control erosion. Native Rhus aromatica is one such plant bred to tackle soil erosion on hills and slopes. For a low-maintenance approach, explore native vines, low-growing evergreen shrubs like juniper, and deep-rooted prairie plants.

Ground covers like lilyturf, Bishop’s cap, Buttercup, and Japanese spurge are excellent choices. However, beware of invasive species like Wintercreeper and periwinkle or myrtle. You can also
consider covering slopes with riprap or various stone coverings, or use shredded tree bark for coverage.

Preparing the Soil on the Slope

Proper soil preparation is essential, whether on a slope or flat ground:

• Clear away existing grass, weeds, and rocks.
• Loosen the soil or add about an inch of topsoil mixed with compost to create a fertile surface for seeds.
• Slightly grade the top and bottom of the slope to make it easier to mow.
• Measure the square footage of the area to determine the amount of grass seed needed.
• Invest in high-quality grass seed that suits your landscape, considering factors like sunlight, shade tolerance, and climate.
• Opt for seeds that resist drought and disease, such as tall fescue or Bermuda grass.

Planting on a Steep Slope (15% or More)

When sowing grass seed on a steep slope, take some precautions. Create a temporary dam, like a
1×4 board, at the top of the hill to slow down rainfall and prevent soil erosion. Before seeding:

• Ensure the soil is moist, about 6 inches deep.
• Apply the seed following the product instructions.
• Use a spreader for even seed distribution.
• Gently cover the seeds.
• Avoid walking on the seeded area.
• Lightly water the newly planted section for 5 to 10 minutes to moisten the soil, reaching a depth of 1 to 2 inches.
• Water twice daily for 10 to 15 minutes, ideally in the morning and evening.
• Until the grass is about 4 to 6 inches high, protect the seeded area with clean straw, cheesecloth, or burlap to shield it from birds, rain, and erosion. You can leave the straw to decompose or rake it from the lawn. Remove the burlap or cheesecloth once the grass is established and growing well.

Slope Hydroponics

For a speedy slope-seeding solution, consider renting a hydroponic grower. This device spreads a mixture of mulch and grass seeds into the ground quickly and efficiently. It’s a method often used after road construction, where water is used to hydrate the seeds. Follow the instructions provided on the hydroponic grower and product labels, and remember to take safety precautions when using electrical power equipment.

Seed Mats or Blankets for Slopes

Though slightly pricier, seed mats or blankets can be one of the easiest and most effective ways to create a lush green lawn on slopes. These mats are typically made of biodegradable materials that eventually break down when watered. Secure the mat in place using turf staples.

One of the advantages of these mats is that they evenly distribute grass seeds, preventing clumps and gaps in your lawn. If you have a large area to cover, check with your local landscaping supplier or garden store to find options that cover more square footage.

Germination usually occurs within 7 to 21 days. To keep the seedlings from drying out, water regularly, providing about 1 to 1.5 inches of water per week. After laying the mat, avoid mowing for 4 to 6 weeks.

Most mats or blankets break down in about 90 days, although this duration can vary. The mulch in these products often matches the color of the soil, camouflaging the seeds as they germinate and grow. Some mats or blankets have netting, which decomposes more slowly. Be cautious not to inadvertently pull out seedlings while dealing with the netting. To avoid issues with the lawn mower, adjust its height if you’re leaving the netting in place until it decomposes.

Overseeding or Slice Seeding on Slopes

You can also rent machinery like over seeders and slicers, which create shallow grooves or ditches in the soil and inject the seeds. This method simplifies soil preparation, primarily requiring you to break up soil clumps and remove rocks. Often referred to as power seeding, this approach ensures excellent seed-soil contact, improving germination.

Core aeration is frequently combined with overseeding or slice seeding. You can rent an aerator, a machine that extracts soil cores about 3 inches deep and places them on the surface. These soil cores resemble dog droppings but gradually decompose over two weeks, enriching the soil with micronutrients. The holes left behind allow water and other nutrients to reach the grass roots effectively.

Best Time to Plant Grass Seeds on a Slope

Fall is generally the ideal season for planting grass, but if your slope is bare, don’t delay. Leaving bare ground exposed for too long may result in weed seeds taking over. You can plant at any time, choosing from seed blankets, mats, hydroponics, or slice seeding based on your preference.

Choosing the Right Grass Seed

For recommendations on the best grass seed for your specific area, get in touch with your local county extension office or visit your nearest home and garden center. They typically stock seeds tailored to your region’s climate and conditions.

When to Seek Professional Help

Managing grass on slopes, especially when it requires regular mowing, can be challenging. Once your lawn is established, consider reaching out to a local lawn care professional who can help ensure your lawn flourishes.