Hello Sharon: Nut trees, just like fruit trees will need to reach a level of maturity before flowering and nut production begins. Over fertilization can stimulate vegetative growth, slowing the maturation process. Fertilizing when young will assist in developing a strong canopy and root system. They benefit from organic matter as a source of nutrients. If inorganic fertilizers are used, literature suggests a ration of 1-2-1. Plants that are deficient in nitrogen will exhibit yellow green foliage.
Best of luck!