Landscape Trellis Drainage

Trellis Placement

• Before installing a trellis, consider the drainage in different areas of the landscape. Avoid placing a trellis underneath runoff from a roof gutter or in an area that pools up when it rains. Runoff flows downhill across landscapes. Avoid areas where runoff causes mud or lots of erosion, which might make the trellis unstable. If you are unsure about the stability of the soil in the area where the trellis will go, support the trellis with cement rather than just sticking it into the soil. Dig holes for the trellis supports and fill the holes halfway with a mixture of instant cement and water. Anchor the trellis in place with ropes while the cement dries, and then fill the holes the rest of the way with soil.

Soil Texture Improvement

• Most vines that people grow on trellises, such as grapes and beans, prefer soils with good drainage. Heavy clay soils drain too slowly, and overly sandy soils do not hold enough water to keep roots moist. Before or after installing a trellis in a landscape, add some organic matter to improve the drainage and moisture retention of both heavy clay soils and overly dry sandy soils. The National Gardening Association recommends tilling some compost into the soil before planting just about anything. Add a few inches of compost on top of the soil, and till it in to a depth of at least 6 inches. Reapply the compost at least once a year to continuously improve the soil texture and drainage.

Drainage Ditches

• Small ditches can help divert excess water away from the bottom of a trellis toward a pond, drain or less important area of the landscape. One way to deal with pooling water in a yard is to create a pond where the water tends to pool and then dig small ditches that lead downhill to the pond. Placing a trellis uphill from the pond will help ensure that the trellis gets enough drainage.

Building a French Drain

• French drains are gravel-filled ditches that direct landscape runoff to an appropriate place, such as a pond or drain. The trench should have a 0.5 to 1 percent slope. To dig a French drain, dig a 2-foot-deep trench downhill away from the trellis toward a good place for runoff to go. Line the trench with geotextile cloth, and place a 4-inch perforated polyvinyl chloride (PVC) pipe along the bottom of the trench. Then, fill the trench with gravel. Instead of pooling up or creating mud near the trellis, water will flow along the French drain to a different part of the landscape.