Grass Roots

In lawn grasses, root structures are crucial in determining their growth, resilience, and overall adaptability to various environmental conditions. Two main types of root structures commonly found in lawn grasses are fibrous roots and rhizomes or stolons. Each root structure has unique characteristics that contribute to the grass's ability to spread, establish new plants, and access water and nutrients.

Fibrous roots:

Fibrous root systems are characterized by a dense network of fine, thread-like roots that spread outward and downward from the base of the plant. These roots are relatively shallow, mostly found in the topsoil, and form a highly branched structure. Fibrous roots are typical in bunch-type grasses like fescues (Festuca spp.) and perennial ryegrass (Lolium perenne).

Some advantages of fibrous root systems include:

• Efficient water and nutrient absorption: The extensive root network enables the grass to access water and nutrients effectively from the soil.
• Erosion control: The dense root structure helps stabilize the soil and prevent erosion.
• Resistance to drought: Although the roots are shallow, the high number of fine roots increases the grass's ability to find water and nutrients, helping it survive short periods of drought.

Rhizomes and Stolons:

Rhizomes and stolons are specialized roots that facilitate the spreading and establishment of new plants. Rhizomes are underground stems that grow horizontally beneath the soil surface, while stolons are above-ground stems that grow horizontally along the soil surface. Both rhizomes and stolons produce new shoots and roots at their nodes, allowing the grass to spread and create a dense, interconnected turf. Grasses with rhizomes or stolons include Kentucky bluegrass (Poa pratensis), Bermudagrass (Cynodon dactylon), and Zoysiagrass (Zoysia spp.).

Some advantages of rhizomes and stolons include:

• Spreading ability: The presence of rhizomes or stolons enables the grass to spread quickly, fill in bare spots, and establish a dense, uniform lawn.
• Recovery from wear: Grasses with rhizomes or stolons can recover more quickly from damage caused by foot traffic or other stressors, as new growth can emerge from the nodes along the stems.
• Resistance to weed invasion: The dense turf created by grasses with rhizomes or stolons can help prevent weeds from establishing and competing for resources.

Propagative roots, such as stolons and rhizomes, are generally shallow, typically found within the top 2-3 inches of soil. These roots are essential for the grass to spread and establish new plants. In contrast, the deeper root structures responsible for sourcing nutrients and water do not contribute to the grass's spreading but are crucial for its overall health and survival. 

Depth of propagative roots and nutrient-absorbing roots in common lawn grasses.

Kentucky bluegrass (Poa pratensis)

Kentucky bluegrass has shallow underground rhizomes, usually found within the top 2-3 inches of soil. These rhizomes allow the grass to spread and form a dense, interconnected turf. In addition to these shallow propagative roots, Kentucky bluegrass also has a moderately deep root system, with roots extending 6-18 inches deep. These deeper roots help the plant absorb water and nutrients, supporting its overall health and growth.

Bermudagrass (Cynodon dactylon)

Bermudagrass spreads through both stolons and rhizomes, which are generally shallow and found within the top 2-3 inches of soil. These propagative roots enable the grass to establish new plants quickly and cover large areas. In addition to its shallow propagative roots, Bermudagrass also has a moderately deep root system, typically extending 6-12 inches into the soil. These deeper roots provide the grass with the necessary nutrients and water to thrive.

Zoysiagrass (Zoysia spp.)

Zoysiagrass has shallow stolons and rhizomes, usually located within the top 2-3 inches of soil. These propagative roots help the grass form a dense, lush lawn that can withstand foot traffic and recover from wear. Apart from its shallow propagative roots, Zoysiagrass also has a moderately deep root system, generally reaching depths of 6-12 inches. These deeper roots help the grass access water and nutrients, promoting its overall health and growth.

St. Augustine grass (Stenotaphrum secundatum)

St. Augustine grass primarily spreads through shallow stolons, which grow just above the soil surface, often within the top 1-2 inches. These stolons produce new shoots and roots at each node, allowing the grass to form a dense, carpet-like lawn. In addition to its shallow propagative roots, St. Augustine grass has a shallow to moderate root system, with roots reaching depths of 4-12 inches. These deeper roots are responsible for nutrient and water absorption, contributing to the grass's health and survival.

In conclusion, the shallow depth of propagative roots (typically 2-3 inches) in common lawn grasses is essential for their efficient spreading and the formation of dense, interconnected lawns. The deeper root structures, which do not contribute to spreading but are responsible for sourcing nutrients and water, play a critical role in the overall health and survival of these grass species. Understanding the depth and characteristics of these root structures can help homeowners and landscape professionals select the most appropriate grass species for their needs, considering factors such as climate, soil type, and intended use.