Apply During the Spring

• Borax is best applied during the spring season when the weather is already warm enough for the ground to be thawed. Borax works well during warm weather and when the soil has adequate moisture. Spring is the perfect time to apply borax since this is also the time that weeds begin to grow in the lawn.
  
  Once weeds are controlled, the lawn has to be mowed, fertilized and watered. All these things must be done on a regular basis to help prevent any weeds from growing back.
  
  

Apply Once a Year

• Borax should be applied only once a year for two years. After that, you should switch to other weed control treatments. This is necessary because too much borax in your lawn can also kill the other surrounding plants. It is normal for the grass in your lawn to turn slightly brown after an application of borax. Don't worry, its vibrant green color will come back in time.
  
  Borax may be a natural weed killer but it also affects the other plants in the lawn. When applying borax, carefully measure it. Make sure you are using just the right amount of borax needed for the size of your lawn. It could kill your entire lawn if you apply too much. Most plants and grass will begin to wilt and eventually die. Sunflowers, however, grow better when applied with a regular dose of borax.
  
  

During the Fall Season

• Another good time to apply borax to your lawn would be during the fall season. During this time, the weather is not yet too cold to alter the effectiveness of the borax. This is also the time when the weeds are storing nutrients for the long winter months they will be underground.
  
  If you spray the weeds with borax while they are storing nutrients, the borax will also be stored along with the nutrients needed by the weeds to grow. If the weeds have borax stored in them while they remain dormant in the winter, chances are they will not survive. If a few manage to survive and grow when spring comes, they will not be as healthy. It will be easier to eliminate them with the use of other natural weed control treatments.