Site Preparation

Site Preparation Methods: 

Proper site preparation is VERY important. Established turf, particularly Bermuda grass, can compete aggressively with young native plants and should be thoroughly controlled before planting. Two site-preparation methods are recommended.

Method 1 — Summer Solarization

Solarization is a lower-cost method that uses summer heat to suppress existing turf and Bermuda grass before planting. This method requires planning ahead and should generally be started during the hottest part of the growing season.

From approximately May through August, cover the entire planting area with clear plastic. The plastic should remain tightly sealed against the ground so heat and moisture are trapped underneath. For the best seal, dig a shallow trench around the perimeter, tuck the edges of the plastic into the trench, and firmly cover them with soil.

Avoid puncturing the plastic with landscape staples, sharp rocks, or other objects. Holes allow trapped heat to escape and can reduce the effectiveness of the treatment. Inspect the plastic periodically and repair any tears or openings.

At the end of the solarization period, remove the plastic and allow the area to rest for approximately 1–2 weeks. Watch for surviving Bermuda grass or other vegetation and manually remove anything that emerges before planting.

Solarization can greatly reduce existing turf, but Bermuda grass is extremely persistent. Continue monitoring the planting during establishment and remove any surviving or invading runners as soon as they appear.

Perimeter edging is strongly recommended where the prairie borders an existing Bermuda lawn. A defined barrier makes it easier to prevent surrounding turf from creeping back into the planting.

Method 2 — Mechanical Removal & Soil Replacement

Mechanical removal provides a faster option when the planting needs to be installed without waiting through a summer solarization period.

Remove approximately the upper 6-8 inches of existing soil and sod, taking as much of the Bermuda grass root and rhizome system with it as practical. A skid steer or similar compact equipment makes this considerably easier for a 200-square-foot plot.

A sod cutter can be used, but it primarily removes the upper layer of turf and may leave deeper Bermuda rhizomes behind. For this reason, deeper mechanical excavation is preferred for heavily established Bermuda.

For homeowners without suitable equipment, renting compact machinery or hiring a local landscape contractor to perform the excavation may be the most practical option.

Once excavation is complete:

1. Cover the entire exposed area with heavy, overlapping cardboard, maintaining at least 6 inches of overlap between pieces. Avoid leaving gaps where existing vegetation can emerge.

2. Backfill the planting area with approximately 5–6 inches of locally sourced topsoil. Local suppliers such as Gem Dirt or Tulsa Topsoil may be suitable sources depending on availability and location.

3. Install the plants according to the supplied planting plan. The cardboard will soften after watering and can be punctured where necessary during planting.

4. Apply approximately 3 inches of locally sourced mulch across the finished planting, keeping mulch away from plant crowns.

Unlike solarization, this method allows the prairie to be planted shortly after site preparation is completed.

Method 3 – Occultation (Opaque Tarping)

Occultation is a low-disturbance, chemical-free method that uses prolonged light deprivation to exhaust Bermuda grass over time. It preserves soil structure and mycorrhizal networks while avoiding the heavy labor and disposal costs of mechanical removal.

This method requires a longer lead time than mechanical removal and is best suited for projects where installation can be delayed 4 to 6 months. In Oklahoma's mild winters, occultation started in fall will not produce significant die-back until soil temperatures warm again in spring. For this reason, fall-start occultation should be treated as a 6-month process, while summer-start occultation may be effective in as little as 8 to 10 weeks.

Timing expectations for Tulsa

· Summer start (June – August): 8–10 weeks. High heat accelerates reserve depletion.

· Fall start (September – October): Plan for 5–6 months. Bermuda goes dormant over winter, so little active die-back occurs from December through February. Kill is not complete until active growth resumes in spring.

· Winter start (December – January): Not recommended. Dormant Bermuda will not exhaust its reserves. Tarps would need to remain in place until mid-summer for acceptable results.

Procedure

1. Mow the existing vegetation as low as possible, preferably to bare soil. Remove any sharp debris that could puncture the tarp.

2. Water the area thoroughly. Moist soil conducts heat more effectively and encourages rhizome respiration, accelerating energy depletion.

3. Cover the entire site with heavy-duty opaque silage tarps (6 mil or thicker, black or black-on-white). Overlap seams by at least 12–18 inches to prevent any light from reaching the soil.

4. Secure the tarp tightly against the ground using sandbags, tires, landscape staples, or buried edges. The tarp must remain immobile—any shifting creates light gaps that Bermuda will exploit.

5. Inspect monthly for blow-offs, tears, or seam separation. Repair any breaches immediately. Even small light leaks can keep Bermuda alive.

6. At the end of the occultation period, remove the tarp and allow the area to rest for 1–2 weeks. Rake off dead thatch and monitor for survivors. Any green shoots that emerge should be hand-pulled, flamed, or spot-treated with a shallow dig before proceeding to planting.

Success indicators

When occultation is complete, Bermuda rhizomes should appear brittle, tan or brown, and hollow when dug up. White, fleshy, or flexible rhizomes indicate surviving tissue. If survivors are widespread, recover the area for an additional 3–4 weeks.

Establishment & Bermuda Control

Regardless of preparation method, regular monitoring is essential during establishment. Pay particular attention to the perimeter, where Bermuda grass from neighboring lawn areas is most likely to creep into the planting.

Pull or dig invading Bermuda while patches are small rather than allowing runners to become established throughout the bed. Maintaining a defined edge between lawn and prairie will make this considerably easier.

The planting is intentionally designed at a relatively dense spacing. As the native grasses and perennials mature, their foliage and root systems will occupy more of the available growing space and increase competition against unwanted vegetation. However, the planting should still be periodically inspected for Bermuda grass and other aggressive weeds, particularly during the first few growing seasons.