As indicated by soil analysis, throughout the growing cycle and particularly in the reproductive phase. Boron is not mobile within the plant, so must be continuously available, although in small amounts. Too much boron in the soil is harmful, so soil analysis testing is necessary. Amounts needed may vary by crop.
Boron is essential for strong, healthy growth, particularly at and beyond the pollination phase. It supports photosynthesis and sugar translocation, root and root nodule growth, pollen tube length, flower, seed and fruit development.