Invasive ivy weed
It appears you have a field bindweed problem. Controlling it by pulling is often a futile endeavor. If you can remove it as soon as it appears, you may be able to deprive the root system of nutrition and it will eventually die. Herbicides are available for the control of bindweed, but may require more than one application to actually eradicate the plant. If you purchase a herbicide, be sure to check the label that it includes controlling bindweed and be sure to follow the label directions. More information on bindweed can be found at:http://ipm.ucanr.edu/PMG/PESTNOTES/pn7462.html and also at: http://www.ipm.msu.edu/agriculture/field_crops/field_bindweed
Thank you! Pulling it, indeed, is futile... I've been doing that for 2 years. Can't keep up anymore. I've never seen it flower, it just strangles my grasses and plants near buy. I will be looking for the herbicide!!