Vertical Mowing

Vertical mowing is a technique that can break up the soil plugs left by an aerator or even remove excessive thatch if necessary. It requires a power rake or a mower whose blades strike the turf vertically. It is done when the lawn is growing most rapidly and conditions for continued growth are favorable. For cool-season grasses, late summer or early autumn is the best time; for warm-season grasses, late spring to early summer is best.

The blades of the vertical mower are adjusted to different heights depending on the objectives of the operation. A shallow setting is used to break up soil plugs; a lower setting gives deeper penetration into the thatch layer, facilitating its removal and relieving compaction of the soil. Deep vertical mowing is only practiced on deep-rooted turfs. Shallow – rooted turfs, often growing mainly in the thatch layer, are harmed more than helped by vertical mowing.


Lawns should be fertilized just before they need the nutrients for their best growth. For example, cool-season grasses derive little benefit from fertilizer applied at the beginning of the hot summer months. Only the weeds benefit from fertilizers that are not timed to coincide with the turf’s needs.

Cool-season grasses should be fertilized in the early spring and early fall. This supplies proper nutrition prior to the seasons of most active growth. Late fall fertilization encourages soft, lush growth which is dam­aged severely during the winter. Warm-season grasses should receive their heaviest fertilization in late spring. Their season of greatest growth is the summer.

A look at Table 13-1 reveals that not all species of grass require the same amounts of fertilizer. As fertilizer costs increase and certain fer­tilizers become less available, turf managers try to maintain plantings with minimal applications. Increasingly, fertilizers with nitrogen in slowly available forms (such as ureaformaldehyde, sulfur-coated urea, or isobutylidine diurea) are being selected by turf management pro­fessionals. Still, the specific amounts needed can vary greatly among species. The most successful mixed species lawns are those that com­bine species whose fertilization requirements are compatible, such as fescues and bluegrasses.

The amount of fertilizer required is usually stated in pounds of nitrogen per 1,000 square feet per year. The number of pounds of nitro­gen in a fertilizer is determined by multiplying the weight of the fertil­izer by the percentage of nitrogen it contains. The examples that follow illustrate.

Example 1

Problem: How many pounds of nitrogen are contained in a 100-pound bag of 20-10-15 fertilizer?

Solution: 100 pounds X 20% N = pounds of N100 X.20 = 20 pounds of N

Example 2

Problem: How many pounds of 20-10-15 fertilizer should be purchased to apply four pounds of nitrogen to 1,000 square feet of lawn?

Solution: Divide the pounds of nitrogen by the percentage of nitrogen.

Four pounds of N ^ 20 percent= pounds of 20-10-15 fertilizer required

4 ^ .20 = 20 pounds of 20-10-15 fertilizer required

To obtain the fullest benefit from fertilizer, it should be applied in an amount the turfgrass can use fully before it reaches beyond the root zone. Lawn fertilizer is usually applied in two stages. Half of the recom­mended poundage for the year can be applied to cool-season grasses in the early spring and the remaining half in the early fall. Warm-season grasses can receive half or more of the recommended fertilizer pound­age during the late spring and the remainder in mid-summer. A spread­er must be used to ensure even distribution of the fertilizer. It is applied in two directions with the rows slightly overlapping.