California Avocado Commission — In spring, as California avocado trees begin to bloom, growers often report seeing yellow leaves at the ends of branches of otherwise healthy trees. Dr. Danny Klittich, of Redox, recently posted an online article about the yellowing of leaves in spring, what this indicates, and what growers can do to remedy the situation.
When avocado trees begin producing flowers, the blooms become major sinks for nutrients — gathering the nutrients they need to set and retain fruit. The timing of fruit development also coincides with the cooler months of the California avocado growing season, when growers tend to fertilize less and the soils, adapting to cooler temperatures, tend to provide less nutrition to the trees. Thus, trees begin to reallocate nutrients from the roots and leaves to the more important task of developing blooms for fruit set. With nutrients reallocated, leaves on the ends of branches may begin to yellow.
According to research, nitrogen, zinc and iron leaf concentrations were lower in chlorotic (yellow) leaves. This makes sense when you consider the importance of each of these to bloom and fruit development. In general, Dr. Klittich recommends that trees should yield a fall tissue sample of 2.5 – 2.7% nitrogen for higher yields. This level provides the tree with an adequate reservoir for bloom development.
Dr. Klittich recommends growers complete the following to improve yield potential.
- Early bud development — During cauliflower bloom and floral elongation, apply nitrogen, zinc, iron, boron and calcium.
- Bloom spray — Nutrient applications should provide calcium, zinc, iron and amino acids and can be made from cauliflower stage through full bloom
- Fruit set — Weekly applications should be designed to support fruit set and development
To view Dr. Klittich’s specific product and dosage recommendations, as well as an informative video concerning avocado bloom strategies, visit his latest online article.