Will Canada Grass Kill Zoysia Grass?

Climate

• Species in the Zoysia genus are warm-season grasses that thrive in temperatures between 80 and 95 degrees Fahrenheit and that tend to stay green in summer and turn brown in winter. Zoysia grass grows best in a southern tier of states stretching from Southern California to South Carolina and located in United States Department of Agriculture 9 through 11. Species of cool-season grasses in the Canada grass blend grow best in temperatures from 65 to 75 F; they typically stay green in cool months and turn brown in summer. The cool season zone stretches from Northern California west to Virginia and north through Canada, roughly USDA zones 4 through 8. These zones are not clearly defined, and there is a transition zone in the mid-south whether either warm or cool-season grasses may thrive.

What's in Canada Grass

• A university analysis of Canada grass shows that it contains 41.3 percent creeping red fescue, 30 percent Kentucky bluegrass and 25 percent annual ryegrass in addition to inert matter, weed seed and inert matter.The annual ryegrass provides the greatest potential for crowding out zoysia grass. All three are cool season grasses.

Spreading Ryegrass

• Annual ryegrass (Lolium multifolorum) is a coarse-textured, light green grass with 1/4-to-1/2 inch-wide blades that taper to a point. When included in seed mixes, its aggressively spreading, dense, branched roots will invade lawns, crowding out more desirable species including zoysia grass. Its rapid growth also means you must mow it more frequently than you mow the grass surrounding it.

Non-invasive Content

• Kentucky bluegrass, (Poa Pretensis) with its deep green, fine blades, spreads by underground rhizomes and grows best during fall, winter and spring, slowing its growth in summer when zoysia grass is green. In Canada grass, Kentucky bluegrass is often mixed with annual ryegrass to give year-round green. Except for cool, shaded sites or in the mountains, red fescue (Festuca rubra) does not grow well in hot climates such as those favored by zoysia grass. Kentucky bluegrass has deep green, fine blades. Because it spreads very slowly by short rhizomes, Kentucky bluegrass is not likely to crowd out zoysia grass. Considering its mix of ryegrass, red fescue and Kentucky bluegrass, Canada grass is not a threat to zoysia grass.