Knowing when to harvest any citrus fruit involves the question of the degree of maturity. Because citrus pass from immature to mature to over- mature slowly while on the tree, the fruit can be harvested over a period of months with small changes in fruit quality. Fruit color is a poor indicator of ripeness. Many fruits have fully colored rinds a long time before they are “ripe”, and others are green when sugars are high enough to make the fruit sweet. Citrus does not increase in sweetness or ripen more fully after being picked-they only decay and dry out!
The only way for you to know if your fruit is ripe is for you to actually taste it! The fruit you taste early in the ripening cycle may be somewhat sour, but will become sweeter as the sugar content rises. Some citrus will ripen late summer or fall from a spring bloom, and others continue to bloom and fruit year-round. Satsuma varieties ripen from October to December from a spring bloom, depending on variety, and Meyer Lemon, limes, kumquats and calamondins can bloom and ripen year round, although many will follow the spring/fall cycle.
Unless damaged by an extended freeze below 28 degrees, citrus will keep better on the tree than when picked and stored. A frost of 30-32 degrees will not injure the fruit or the trees, and covering the tree will prevent lush new growth from damage. If you grow your citrus in pots, be sure to move it to an area that will not freeze if an extended freeze is predicted. When you are ready to begin harvesting your citrus, pick the fruit from the lower branches first. Low hanging fruit is more likely to be damaged by the cold near the ground and brown rot fungus may splash from the soil onto the fruit hanging low on the tree.
For a longer harvest period, plant different varieties of Satsuma mandarins (which have varying ripening times), Mexican Limes and Meyer Lemons. Remember, Arctic Frost Satsuma and Orange Frost Satsuma varieties are the most winter hardy for our area. Meyer Lemons are somewhat hardy, and Limes are not cold tolerant at all!