How to Plant Grass Seeds on a Slope
Updated: Sep 7
You love the way your landscape slopes down the road and you dream of days when green grass blankets the space. However, getting grass to grow on bare slopes can be difficult. Here you'll find tips on how to plant grass seeds on your slopes to help make your dream of beautiful green carpet a reality.
What is a slope?
Tilt is how much the Earth's surface rises or falls. As part of the land's topography, slope is an essential measurement for understanding drainage and how water moves across an asset. Numerically speaking, slope is the change in elevation over a given distance. That is, the number of feet the ground rises and falls over a horizontal distance. What way does it fall? How to measure the slope of your yard? Slope is often described as a percentage. For example, an area raised 12 feet from a distance of 100 feet has a slope of 12%.
Why is slope important?
Slope is an important factor when planting lawn seeds and maintaining your landscape for a number of reasons.
Slope is also important when sowing or planting grass and when mowing. Several organizations, community say the steepest grade is 15%. Others says grass slopes should be less than 20%.
Planting grass seed on slopes greater than 15% is to prevent turf loss through soil erosion. Keeping grass seeds in place even on a 15% slope can be difficult.
Steep slopes can be dangerous when mowing with a walk-behind or ride-on mower. When walking behind the mower, it is easy to slip on steep slopes. Riding mowers may tip over.
What if the slope is too steep?
If the slope is too steep and dangerous to mow, consider an alternative. Typically, slopes are planted with low-profile plants less than 4 to 5 feet tall when fully grown. This is especially true when you want to view the scene from the bottom of the slope.
Terrace the slope by adding stone, timber, or low retaining walls horizontally every 3 to 4 feet as you go down the slope. Terraces do not have to be the same size and shape. Some may be round or flowing. Add plants to the cascading sections.
Choose plants with strong, deep roots that help control erosion. A native Rhus aromatica, was bred to control soil erosion on hills and slopes.
You don't have to go down steep hills to find and care for plants that require less maintenance. For native vines, low-growing evergreen shrubs such as juniper are good choices.
Deep-rooted prairie plants and grasses add flowering perennials to the mix. Sedges adapt well to many environmental conditions.
Ground covers such as lilyturf, Bishop's cap, Buttercup, and Japanese spurge are just a few that grow well. Avoid invasive species: Wintercreeper and periwinkle or myrtle.
Cover slopes with riprap or other types of stone coverings, or cover slopes with shredded tree bark coverings.
Soil preparation on the slope
Preparing the soil on a slope is the same as preparing it anywhere.
Remove grass, weeds and rocks.
Roughen the soil or add about an inch of topsoil mixed with compost. This creates a loose surface for seeds to adhere to.
Grade the top and bottom of the slope to flatten it slightly. This will reduce the chance of the mower scratching the area.
Measure the square footage of your area to determine how many lawn seeds to buy.
Buy the best grass seed you can afford.
Choose seeds that will work for your landscape: full sun, shade tolerant, warm or cool season varieties.
Find seeds that will produce weeds that are resistant to drought and disease.
Deep-rooted grasses, such as tall fescue, are one type recommended for northern lawns. Bermudagrass has deep roots. Rye germinates quickly and can help keep the soil in place until deep-rooted grasses take hold.
How to sow a slope of 15% or more
When planting grass seed on a steep slope, place a temporary dam, such as a 1x4, at the top of the hill. This helps slow rainfall and reduce soil erosion.
Sow seeds on a slope
Depth - about 6 inches deep - this is the area to be planted a few days before sowing the grass seed. Moisture helps maintain seeds and initiates the germination process. Insert a long screwdriver into the soil and pull it out. Look for signs of damp dirt on the metal part of the screwdriver. You can tell how deep the soil moisture is by measuring how many inches of moist soil there are with a screwdriver.
Apply the seed according to the directions on your lawn seed product. The label will tell you how to set the seed spreader to apply the correct amount.
Crossing the area with a spreader is usually a good idea.
Lightly scrape the seeds to cover.
Do not walk in the seed area.
Lightly water the newly planted area for 5 to 10 minutes to moisten the soil and water 1 to 2 inches deep.
Water is given twice a day for 10 to 15 minutes. Breakfast and dinner are best.
Until the grass is actively growing, cover the sown seeds with clean straw, cheesecloth or burlap to protect them from birds, rainfall and erosion. Straws can be left to decompose or raked from the lawn. Remove the burlap or cheesecloth once the grass, usually 4 to 6 inches high, is in place.
Once the grass is established, the roots must control soil erosion.
Slope hydroponics
You can rent a hydroponic grower that spreads mulch mixed with grass seeds into the ground. In this way, slope seeding can be carried out quickly. Stand and spray where you can hit all areas.
You may have seen this method used to seed an area after road construction. Because water is part of the process, the seeds are instantly hydrated. Follow hydroponic grower and product label instructions for subsequent watering.
TIP: Take appropriate safety precautions when working with electrical power equipment. Wear eye and ear protection, gloves and closed-toe shoes.
Seed mats or blankets for slopes
Although more expensive, a mat or blanket with grass seeds and fertilizer can be one of the easiest and best ways to create a green lawn for your slopes. Most mats and blankets are made from materials that decompose. The mulch will eventually break down if you lay down a blanket or mat and water it. Secure the mat in place with a turf stapler.
One of the advantages of these blankets or mats is that the grass seeds are evenly distributed, resulting in a turf without clumps or voids. If you have a large area to treat, check with your local landscaping supplier to see if your lawn and garden store has options to treat more square feet than are available.
Germination usually occurs within 7 to 21 days. Regular watering of about 1 to 11⁄2 inches per week is required to keep the seedlings from drying out. Lay down a mat and withhold mowing for 4 to 6 weeks.
A mat or blanket should break down in about 90 days, sometimes shorter or longer. The mulch that carries the seeds to the ground may be of a color that camouflages the seeds as they germinate and grow.
Some mats or blankets are made of netting, so decomposition can be slower, and when weeds take over, many people end up pulling nets. This can be dangerous as you can pull out seedlings that are still growing. However, be careful with the netting so it doesn't get tangled in the lawn mower. If you are leaving the netting in place until disassembly, increase the height of your lawn mower.
Overseed, slit or slice seeding on slopes
Planters and mowers are also available for rent. They make shallow grooves or ditches in the soil and inject the seeds. Each of these machines is useful for repairing flaky patches or renovating low-growth areas.
This method often eliminates much of the soil preparation except for breaking up soil clumps and removing rocks. Also called power seeding, this method is more efficient than roughening the ground and planting weeds. This equipment helps germination by ensuring good contact of the seeds with the soil.
Core aeration is often accompanied by overseeding or slice planting. You can rent an aerator. The machine pulls a core about 3 inches out of the soil and places it on the surface. Cores resemble dog droppings. But as it decomposes over two weeks, it adds micronutrients to the soil. Meanwhile, the holes allow water and other nutrients to reach the roots of the grass.
When is the best time to plant grass seeds on a slope?
Fall is generally the best time to plant a lawn. But if the slope is loose, sow the seeds as soon as possible. If bare ground is left too long, weed seeds will fly in and take their place. You can do it anytime with your choice of seed blanket, mat, hydroponic or slice sowing.
How do I know which grass seed is best for my area?
Contact your local county extension office for grass seed recommendations for your slopes. Local home and garden centers also have suggestions. They usually only have seeds that are best for your area.
When to call a lawn care professional?
Maintaining grass that grows on slopes can be difficult, especially if it requires mowing. Once your lawn is in place, connect with a local lawn care professional who will do everything in his power to keep your lawn growing.