Late Hanging Navels

By Nick Sakovich

Over the past few years, Australia has been producing approximately 575,000 metric tons of total citrus per year. By far, the majority of this production is oranges, with about a 60/40 percent split between valencias and navels. Their Washington navels mature in April-May and can be stored on the tree until September-October.

Early on, the Lane Late variety had been selected, commercially grown and shown to retain its fruit for about one to two months longer than the Washington navel. In the mid-1980’s gross returns from Lane Lates often exceeded A $25 per carton compared with A $10 for the Washingtons. This large difference prompted interest in identifying other clones of navels which might store fruit even longer. Many growers claimed to have found several selections of navels, which stored fruit on the tree for one to three months after the Lane Late harvest. Since the mid-80’s, SARDI (South Australian Research and Development Institute) has stepped in to investigate these claims.

SARDI was established by the South Australian government to fund and direct research in agriculture, horticulture, livestock and the aquatic sciences. Under the direction of Dr. Peter Gallasch, considerable research has since been conducted on the late hanging selections of navel oranges. Trials were established in five different regions of southern Australia. The 1994/5 season was the first season in which trees in some of the areas produced sufficient fruit to be analyzed.

Fruit quality data (fruit size, flavor, sugar, acid and juice content and external appearance) obtained from all three seasons (‘94/5, ‘95/6 and 96/7) was similar although not identical. In the first season, Wiffen, Powell, Summer Gold, Hutton, Christensen and Autumn Gold had the best internal fruit quality. Over the next two seasons, Wiffen, declined and dropped out of the top group, due mainly to small fruit size. Christensen and Summer Gold also dropped out of the top group, while Chislett moved up with Hutton, Autumn Gold and Powell. Barnfield and Rohde are included in the second group. Wiffen tends to have small fruit while Rohde produces large fruit. Lane Late consistently produces fruit with thicker skins, more granulation and lower juice content. Other differences between Lane Late and the other late navel selections are minimal.

Harvests of these new selections could be extended one month later than Lane Late.P>For yields, Rohde, Neilson and Wilson are at the top; Summer Gold and Wiffen gave some of the poorest yields, while Lane Late is an intermediate yielder.

In summary, Australia ranks their late hanging navels as follows:

The top group to consider for planting – Hutton, Powell, Autumn Gold and Chislett.

The second group – Rohde, Wilson, Neilson, Barnfield, Christensen and Wiffen.

Researchers from all over the world need to, and do share information.

However, a word of caution. The above information comes from good, sound scientific research, but it is from Australia, a different geographical and climatic region. Whether one is speaking about rootstocks trials, varieties trials, or even insect pests, remember, it’s the location. Even within California there are distinct climatic differences, and one should not rely heavily on results of a trial conducted, for example, in the desert when one is growing trees in coastal Ventura County. So we must be very careful in using Australian data for plantings in California. Other cautions include knowing that we are using genetically identical material in all tests and being aware of viruses that may be infecting trees in one area and not in another.

Dr. Tracy Kahn, of the Department of Botany and Plant Sciences, at the University of California, Riverside, is presently evaluating six different cultivars of the late hanging navels at nine different locations in California (Central California and Ventura County). She currently has three years of data. Although it is definitely too early to make any recommendations, a few observations can be noted. 1) Fruit size in the Barnfield variety is large (average 48’s), 2) Summer gold matures the earliest,
indicating that perhaps it should be put in the category of ‘navel orange’, as opposed to a late navel and 3) granulation was most prevalent in Lane Late fruit and occurred first in some areas of the San Joaquin Valley and lastly in the Ojai Valley (Ventura County). In the only two SJV locations that Barnfield was evaluated, it also had prevalent granulation.

Although growers are anxious to receive good scientific data in order to make appropriate decisions, a quick decision may turn out to be a bad one. It is still too early to make a precise evaluation of which late navel to plant. And to complicate matters, California has such diverse climatic areas, that data coming from a coastal trial may have no relevance for growers in warmer inland areas, and vise versa. That is why the California trials are so important; they are located in so many different climatic zones, and each year as more of the data comes in, they will prove invaluable to growers.