The Last of the Boron

I sprayed the lawn with the last of the boron for the year, one teaspoon per thousand square feet. That should be enough to raise my boron levels from 0.4 PPM to around 0.8 PPM.

Boron's role in plants isn't clearly understood. It does help meristem cells differentiate into blade and root cells. Lacking it, the cells elongate but don't differentiate. Grasses aren't particularly sensitive to boron deficiency, but it's always best to adjust micronutrients into the optimal range if you're comfortable doing so.

Boron is also the touchiest of the micronutrients. 0.4 PPM is slightly deficient, 0.8 PPM is optimal, and sensitive plants will begin showing toxicity symptoms around 1.0 PPM. Only add boron after a soil test shows that your soil is deficient.