The optimal time to use herbicides to control bindweed is in the fall, when the plants are channeling nutrients down to their deep root systems to prepare for winter dormancy.
Applying herbicides during this period ensures the chemicals are effectively transported to the roots along with the nutrients, increasing the likelihood of complete eradication.
Moreover, treating the weed in the fall minimizes the risk of harming other garden plants, as many have already died back or become dormant by the time the first frost arrives.
If bindweed is spotted before planting summer crops, you can also apply herbicides in the spring, provided the vines are at least 10 inches long to ensure sufficient absorption.
Throughout the summer growth season, regularly pulling out the weeds or cultivating them every other week can help deplete the plant's resources and prevent it from taking hold.