Lemons - Late August through mid March
The most obvious characteristic of lemons is that they are acid rather than sweet. The acid content is actually at the maximum prior to full fruit maturity. For commercial purposes, this means they are picked by size rather than by ripeness. The earlier they are picked after they obtain sufficient size and juiciness, the more acidic they are and, therefore, the longer they can be stored. “Lisbon” and “Eureka” variety lemons are the major commercial varieties grown in the Arizona Desert. The fruit of these varieties are difficult to tell apart. Characteristically, both varieties produce juicy, highly acidic fruit with very few seeds. However, the “Eureka” variety lemon tends to size sooner, is slightly more thick skinned, is longer in shape, and often shows almost imperceptible vertical ridges on the exterior surface of the skin. Average fruit size ranges from 2 to 2½ inches in diameter.
Lemons are commercially packed into three grades - U.S. No. 1 (Fancy), U.S. No. 2 (Choice), and Standards. While the vast majority of lemons are packed into a standard two-piece fiberboard carton holding approximately forty (40) pounds, lemons are also packed into six-count, two, three, and five pound bags and a food service carton equivalent to approximately a quarter carton of lemons. Commercial sizes of lemons based on how many pieces of fruit are packed into the standard forty pound carton include 63's, 75's, 95's, 115's, 140's, 165's, 200's, and 235's.
The most common defect that causes a lemon to be downgraded from a U.S. No. 1 to either a U.S. No. 2 or Standard is oleocellosis. Climatic conditions in Southwest Arizona from August through October are characterized by extremely hot humid days and very warm humid nights. Because the best lemons are grown in sandy, well-drained soil, under the above conditions irrigation is required no less than every fourteen days. Irrigation causes the turgor pressure of the rind of the fruit to increase. Oleocellosis, also known as oil spotting or green spot, is caused by the phytotoxic action of peel oil released onto the surface of the rind as a result of hand harvesting the lemons. The disorder is called “green spot” because areas of the rind affected by the peel oil from broken oil sacs on the rind do not degreen as the rest of the surface of the lemon turns from green to yellow when one part per million ethylene gas is added during the curing process. Prior to harvesting, pressure testers are used to measure the pressure at which oil sacs rupture to determine when the pressure is low enough to permit safe harvesting. However, as it normally takes three days to harvest the typical lemon grove that is being irrigated every fourteen days, the grove must be harvested beginning on the eleventh day or risk not being harvested until after the next irrigation cycle. The Harvesting Superintendent must “walk a fine line” between oleocellosis and maintaining an adequate supply of lemons to the packinghouse. Harvested lemons are left in the grove overnight in the bins they were harvested into to allow the turgor pressure to continue to decline to permit safe transport to the packinghouse without causing additional oleocellosis problems. Damage caused by oleocellosis is cosmetic only and should not be confused with skin- or rind-breakdown and peteca. Oleocellosis does not affect either the transportability or shelf life of packed lemons.