FAQ

The true answer is: you don't. But you can slow it down and manage it. 

Field bindweed, often called morning glory, is indeed enjoying the hot summer we are having this year. It is just the edge it needs to compete more effectively against the cool season grass lawns most of us grow. As with any weed management, irrigation practices are important, although less so with this weed, since it grows from roots. But it also produces seed which can germinate and grow quickly in the right situation.

Water lawns only as often as absolutely necessary. By allowing the top one inch of soil to dry between irrigation, you are killing any weed seeds that are sprouting immediately after the irrigation. Train the Turfgrass to grow deeper roots by wetting the soil at least 8 inches deep every time you irrigate. Test it by digging a hole and looking at the soil or by poking a long screwdriver down into the lawn - the dry soil begins when you meet resistance. Thatch buildup creates a good place for weeds to germinate, because this spongy layer between grass blades and the soil retains water longer than soil would. If thatch is thicker than one-half inch, core aerate this fall or late summer (once hot temperatures subside). Too much nitrogen fertilization can lead to thatch buildup, because grass is growing faster than the clippings and dead roots can decompose. Also, don't forget to raise the mower deck so that the soil surface is more shaded, this will discourage weed growth there. Taller grass plants grow deeper roots, so you can go even longer between irrigations thus allowing the soil surface and/or thatch layer to dry out and kill weed seed that may be germinating.

Review the USU Extension publication "Basic Turfgrass Care" and make sure that your lawn care company is following the maintenance guidelines therein. You can download that publication at 

http://extension.usu.edu/files/gardpubs/hg517.pdf

When temperatures are cool enough (80 daytime max), and bindweed is in the lawn, you can spray it with an herbicide containing 2,4-D. You cannot spray these weedkillers while temperatures reach above 80 for one or two days after spraying, because the chemical will volatilize and float over to nearby plants and damage them. In areas where there aren’t any other desired plants, you can spray bindweed with a broad spectrum herbicide containing glyphosate (like Roundup).http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7462.html

Bindweed is really loving our hot weather, because our Kentucky bluegrass is heat stressed and not competing well. A vigorous, healthy lawn can usually out-compete bindweed.  Three to four inches of mulch over soil will keep bindweed under control, too.

Maggie Wolf

Utah State University Extension

Horticulture and Technology Agent

This weed is correctly called field bindweed.  It is a very difficult and persistent problem.  The plant propagates by seed and underground rhizomes.  Early “weeding” of young plants reduces and sometimes eliminates their growth.  However, established plants with a deep root system are extremely hard to control and a broadleaf weed killer should be applied during the blooming season or in the fall after the first frost. 
Recommendation:  Grow a vigorous lawn to compete against bindweed, or apply mulch 3 inches deep over it.  Occasionally pull sprouts or spot-treat with perennial-rate glyphosate.

Utah State University Extension

Master Gardener