Will Vinca Choke Out Grass?

Description

• The two main species of Vinca are lesser periwinkle (Vinca minor), which is hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 4 through 8, and greater periwinkle (Vinca major), which is hardy in USDA zones 7 through 9. Both species produce tubular, lavender-blue flowers. Lesser periwinkle flowers are 1 inch wide and appear from May to June while greater periwinkle has 3-inch-wide flowers from April to May. Greater periwinkle’s leaves are up 3 inches long while lesser periwinkle’s foliage grows to about 1 1/2 inches long.

  Both species feature long, trailing stems, but greater periwinkle creates a carpetlike mound that is about 6 to 18 inches tall; lesser periwinkle mounds to a height of about 3 to 6 inches. Both plants will spread across the ground indefinitely if allowed. They grow in a range of conditions but perform best in a site that receives full sun to partial shade and has dry to moderately moist soil. They can, however, thrive in dry or rocky soil and dense shade, and they tolerate drought and deer foraging.

Invasive Potential

• Lesser periwinkle and greater periwinkle are considered invasive in some areas and can choke out turf grass, native plants, perennial garden plants and weeds. The periwinkle plants form a dense mat that rapidly covers the ground, excluding other plants by competing for nutrients and water. They can spread extensively; their arching stolons, or runners, root at the tips, covering the ground wherever they contact soil. If the weather turns cold or dry, the plants' growth may slow, and die-back may occur. When favorable conditions return, however, the plants recover quickly.

Mechanical Control

• Although hand pulling, raking or digging out periwinkle plants is labor-intensive, it can be an effective means of control if you remove all their root nodes and stolons from the soil. If when pulling out the plants you have to pause or pull them in stages, then begin at the perimeter of a periwinkle patch and work toward the patch's center, pulling the plants in on themselves to prevent them from spreading. Mechanical control such as pulling the plants by hand typically takes several growing seasons to eradicate a patch of periwinkle plants. So repeat pulling them about every three months to remove resprouts. After the periwinkle is removed, check the area twice each year -- late spring and early fall -- for new periwinkle growth.

Chemical Control

• If you want fast control of periwinkle plants, then chemical control may be more effective than mechanical control. Cut or mow the periwinkle plants during late spring to early fall, and apply a 5 percent solution of a glyphosate-based herbicide immediately on periwinkle resprouts. Wear a long-sleeved shirt and long pants as well as gloves and safety glasses when applying the herbicide, and follow all of the herbicide's label instructions about how much of the herbicide to use, how to apply it and safety precautions. Thoroughly wet all periwinkle leaves with the herbicide, and continue cutting and treating the plants with the herbicide from July through October. Cutting or mowing the plants ensures that the herbicide penetrates their waxy cuticle. Eradicating established periwinkle plants can take several growing seasons. Monitor their regrowth, and follow up with repeated cutting or mowing and herbicide applications as soon as new growth appears.