Vertical mowers and dethatchers

Thatch is a layer of decayed and partially decayed turfgrass-plant parts-such as stems, roots and sometimes leaves-that accumulate over time. Plant parts that are most resistant to decay and that are the prime culprits to thatch development are stems, including rhizomes and stolons. Leaves generally decompose rapidly and don't contribute to the thatch layer unless the layer is already deep. Although some thatch provides resiliency to the turf, excessive thatch is detrimental. Generally, that excessive depth threshold occurs between 0.5 and 1 inch.

Only certain types of turfgrasses are prone to thatch development-those that produce rhizomes or stolons. But, unfortunately, these rhizomatous and stoloniferous turfgrass types include such prevalent species such as Kentucky bluegrass, fine fescues, bermudagrass and St. Augustinegrass, which are commonly used as lawns.

The problems you encounter with excessive thatch are many. Thatch reduces water infiltration into the soil, and turfgrass tends to restrict its rooting to the thatch layer. Consequently, turfgrasses generally develop shallow rooting in heavy thatch. This makes them less tolerant of droughty conditions.

Thatch also harbors diseases and insects. The high organic content of thatch is a food source for some disease organisms that also can attack turf. Thatch also creates a good environment for insects, because it acts as a haven in which insects hide and breed. Furthermore, insect damage and disease occurrence can be more prevalent in thatch because insecticides and fungicides can bind to the organic matter in thatch and reduce their effectiveness. Mowers also tend to sink into deep thatch, thus increasing their likelihood of scalping the turf.

You can help manage thatch by creating conditions that accelerate decomposition, such as maintaining proper pH, avoiding excess nitrogen, topdressing and aerating. However, once you have a deep thatch layer, your only practical alternative is to remove it with mechanical dethatching equipment. Dethatching equipment includes three basic types: vertical mowers, flexible-tine dethatchers and multi-purpose dethatchers. (For more information on the variety of available products, see related product descriptions that accompany this article.)

When choosing a dethatching unit, consider the size of the area you maintain. Also consider whether you have lots of trees, shrubs or other obstacles around which you must maneuver. Both of these aspects will have an impact on the type of unit you choose to purchase.

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