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I r .~tllt~If':'1I1ro1r=w Figure 3: Mowing height affects turf density and root length (adopted (rom Ferrara 1992) I I I I I I II I I I I I I I f" I Healthy grass Hol\' LOH' ro Mow? ?,v1owing height is critically important. Traditional lawncare looks 10 {he close-cropped putting green as the ideal turf. Unfortunately, close mowing can weaken the grass and expose the grass crowns to sunburn. It J!so ~xposes the soil to sunlight, which may encourage weed seeds to germinate. Keeping grass taller will aClllally shade out weeds. reducing them by more than 50",0 (Alliance for the Chesapeake Bay 1994). Mowing taller also encourages thicker turf and deep roots (Fig- ure 3). Many grasses spread through stolons (shoots that run along the ground and produce a new plant at the tip) or rhizomes (underground horizontal stems that produce new plants). Since the blade tips contain chemicals that inhibit side .shOOlS, mowing can stimulate the growth of sto- lons or rhizomes. However, turf trials at Purdue Uni- vc::rsity found [he spread of grass varies with mowing heig.ht. After 22 weeks, a freshly~sccded lawn that was mowed 10 V4 inch height covered 42% of its plot. In contras.t, a L1wn mowed La 3 inches covered 80% of its rIot (SchulLz 19R9). Mowing high encourages deep foots hl.:causc with more leal" surface, lhe gruss plants ;m; ;ihlc: to manufacture mure fond. Researchers at lhe Michi~;'Jn Af!ricullur~1 Station found,closely cropped gCIS;'; (J inch mowing height) had less rool growth and :--.11(j()1 regrowth, as. wdl as fewer I;llcral stems (Schultz I ()Xt)). T:ihk 3 gi'le:) general fIllJwi ng heights for d i rtl.:rcllt gr:lss species. Mowed too close Mowing Frequency and Thatch Management Mowing frequency is also important. Mow too much or too often, and the grass can be damaged_ To keep the grass healthy, it is recommended that no more than onc-third of the leaf be cut at a time. While [ollowing the "one-third" rule may mean mowing more fre- quently, it does not necessarily mean spending more time ~ehind the mower. This is due to the fact that grass grows at different rates throughout the year. ~~"",,"i\lliU\I\\J~l\\\V,.~~\'.:l.1!l1 When the grass is growing rapidly, it may be necessary to mow twice a week, At othcr times. mowing twice a month may be sufficient. Lastly, homeowners should learn how to recognize and measure thatch; 100 mueh thatch (over 112 inch) is a sign of unhealthy grass. poor mainLcnance, and/or compacted soil. Thatch is a brown. straw-colored layer between tbe green grass and the soil. A small tholch layer is actually helpful. it functions like mulch in a fluwer-bed to conserve moisture and block wecds. When thatch i$ deer it may keep water, air and nutri- ents from rcaching the grass rOOIS, Shallow watering, ovcrrcrtili7_ation and close mowing ..III can increase the (hatch layer. Practicing low inrut lawnci.lrc and aeral- ing the soil can prcvc:-nt cxces:-;ivc thilleh build-up. If thatch huikl-up has occurcd and sprinkle compost ov(:r the bwn (a practice called tor dfessing) and acrate 10 cncourage thatch Jccomposili()fl. ~~\'illJ>lt'\\\J~""V.,/.'";:;r.'i;~~I'~l Keeping grass tall (3 inches or higher) can prevent weed germination and lead to better root growth. Watershed Pfolecllon Techniques _ Vol. 2. No.1_ Fall 1995 259