We have many different avocado trees surrounding our yard. They are all seedlings, progeny of the two mythical side-by-side trees down on a remote dirt road in Kapoho about 30 years ago. One of them was a big, round purple fruit with rich, buttery flesh, and the other a monster pear shape with very pale green skin, tiny pit and excellent flesh.
So, when we returned decades later to build our home, we went down and found the trees and dug up the seedlings. It has been fun trying all the different fruit that have resulted.
My question is this — a few of the trees produce really high quality fruit most of the time, but some of the years they will have strings and others not. Any idea what causes this sort of variation?
Thank you so much, Vicki
First, as you mentioned, the trees are not grafted which means that they were produced from two ‘parent trees’ down the road. These seedlings are, therefore, a mix of genes producing truly individual trees. Seedlings are different from the parent tree whereas grafted ones produce a tree identical to the “mother.”
The strings in the fruit are vascular tissue, part of the conductive system of the plant bringing water and nutrients to the fruit. They are always in the fruit but soft and unnoticeable in high quality fruit. Some seedling trees produce vascular tissue that is more pronounced or stringy. The stringy characteristic should not vary from year to year; what will vary is the color of the tissue. It is usually the same color as the fruit pulp but can discolor or blacken for various reasons. The most common reason is cold temperatures, but that’s a problem in California and does not pertain to fruit grown in Hawaii.
For some genetically mixed trees, it is the nature of the fruit to exhibit darkened strands as the fruit reaches maturity and beyond. This means fruit exhibiting this characteristic may be past its prime.
The situation you describe, only occurring some years, is most likely a disease. There are a number of fungi which enter an avocado at the stem end of the fruit. Some of these pathogens will cause vascular discoloring as a precursor to decaying the flesh.
These stem-end rotting fungi are present in the soil and on dead plant tissue and assist in the breakdown of organic matter. Their spores spread by wind and splashing water. This disease is clearly made worse in a rainy environment. Infection typically occurs when the fruit is still on the tree, but it does not develop until after the fruit is picked due to anti-fungal compounds present in unripe fruit. Fruit will continue to decay as it ripens.
Control Measures: Since these fungi attack dead plant material, cleaning out dead limbs and twigs helps to reduce the incidences of fruit rot. Keep trees healthy with proper nutrients and water. Maintaining a thick layer of mulch under the tree’s canopy also helps to minimize the disease. After the fruit is picked, dry it and place in the refrigerator if not eaten soon. Caution: Temperatures below 41 degrees Fahrenheit can cause fruit injury in some varieties. For severe problems, trees can be sprayed with a copper fungicide to limit infection.
How long would it take breadfruit trees to produce fruit if planted on the wet side of Waimea? Do they grow well there?
Breadfruit trees will begin to develop fruit in 3-5 years after planting. The trees grow on the Islands from sea level to 5,000 feet elevation, in areas receiving 60-120 inches of rain. They also thrive in a wide range of soils, but roots need good drainage. They should grow well on the wet side of Waimea.
Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at firstname.lastname@example.org.