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Citrus have special requirements for maintenance and harvesting that differ in some respects from deciduous and temperate fruit trees such as apples and plums. Below are tips to help you optimize harvest and avoid pitfalls.
Most citrus fruits are ready for harvest beginning between about December and February in California, but some varieties ripen at other times of year. Every type and variety has a different harvest window, and the exact window may vary based on factors including local seasonal weather, environmental conditions, and tart/sweet flavor preferences of the citrus eater.
Timing your citrus harvest accurately requires getting to know each of your citrus varieties. Full-sized fruit indicates that the harvest period is approaching, but mature size in itself doesn’t indicate ripeness, and under conditions of drought, insufficient sunlight, environmental or other stressors, and/or infertile soil, trees may produce small fruit that ripen properly and are delicious.
Color is another indicator, but some varieties may require weeks to months to reach full sweetness after fruits appear fully colored. Start by checking the approximate harvest window in your area, then sample a single fruit that appears ripe. When one fruit on a given tree is ripe, generally the majority of others, or at least those with the same coloration, are also ripe.
Avoid harvesting or eating immature citrus fruits. When citrus fruits are immature as indicated by small size and lack of mature color, they are so high in citric acid as to be unpalatable or even potentially harmful to eat.
That’s a tricky question, not least because ideal citrus flavor varies with each grower and eater. Technically, genetics determines the flavor of fruits each citrus produces. However, there are a few tricks that can affect flavor, sweetness, and sweet-to-tart flavor balance of citrus fruits.
Unlike most temperate fruits, citrus fruits don’t continue to ripen after they’re removed from trees. If you like sweet citrus fruits, it’s important to leave the fruits on the trees until they’re fully ripe, which may take a few to several months or even longer after the fruits are full-sized and fully colored.
The single most-effective way to increase flavor and sweetness in citrus fruits is to stop watering a few to several weeks before harvest. Genetics determine the type and degree of flavor in citrus; however, when individual cells in citrus fruits contain less water compared to their natural flavoring biochemicals and sugar, the fruits taste stronger or sweeter. For most established trees, stop watering about 3-to-5 weeks before harvest to improve sweetness and flavor without causing major water stress. As the majority of citrus varieties ripen during winter in California, the Mediterranean rainy season may supersede your plans to delay watering. Also your trees may have roots in neighboring properties where you can’t control watering.
Citrus are also different than temperate fruits in that they progress from acidity (tart or sour flavor) to sweetness the longer fruits remain on a tree. If you like tart citrus fruits, harvest early in the seasonal window for your variety. If you like sweet fruits, leave fruits on the trees for several weeks to a few months or longer.
For those who love acidic flavors, there may be nothing quite like the toe-curling zing of an early-harvest lemon in late November, or the flavorful kick to the tongue of a barely ripe orange in early December. Eating citrus early in their harvest window is similar to eating hot peppers: it provides a potentially adrenalin-fueled experience and body sensation that’s experienced as much as tasted. For the rich luscious sweetness of California-grown mandarins and oranges, you may have to wait weeks to months.
The temptation to grab and pull may never be stronger than when you see a luscious ripe citrus fruit within reach in your own backyard. This is a popular harvest method, but often damages trees, tears bark, and reduces future harvest by removing fruiting twigs. It even may harm the fruit itself. Instead, use sharp, sterilized pruning shears for a clean cut on the stem close to the fruit.
If harvest can’t be delayed when you can’t find your pruning shears, try twisting the fruit back and forth a few times with one hand while holding onto the twig attached to the fruit with the other hand.
In California, the greatest threats to your citrus harvest are usually squirrels and rats. If your trees are sufficiently watered but citrus fruits still drop, especially if your citrus fruits show small nibbles, squirrels are likely sampling your harvest. On the other hand, rats often eat an entire fruit while leaving a ragged portion of rind still attached to the tree.
There aren’t many good options for preventing citrus damage by squirrels and rats. GardenZeus recommends physical exclusion by encasing the fruits. While this is a bit tricky and can be time-consuming when you first make the cages, it remains the best option we know to ensure that you’ll enjoy at least some of your citrus harvest. Use half-inch hardware cloth. Plastic mesh and most other barriers are easily shredded by rodent teeth. Measure length of hardware cloth needed to enclose groups of fruits and until you’ve installed a few cages, it’s best to allow more than appears will be needed for installing cages around fruits. Use wire snips for cutting and plant twist ties to close cages around fruits. Use caution after cutting as wire edges are often sharp and the hardware cloth tends to snap back without warning toward its original rolled shape.
Citrus fruit drop is usually caused by insufficient watering. Various fungi and bacteria may harm citrus but they usually affect only a small portion of fruits. For more info about both topics, see Harvesting Citrus in the Home Garden: Preharvest Care.
All citrus varieties are sensitive in varying degrees to frost damage. Freezing temperatures harm flowers and fruits. If frosts are possible in your area, monitor weather and harvest before periods of possible frost. To increase the frost resilience of citrus for short periods of time, make sure your citrus trees are well -watered and covered with sheets or tarps. Almost any cloth, plastic, or paper sheet of sufficient size can be used. The goal is to create a pocket of slightly warmer air under the cover but over the citrus and to prevent air moisture from settling and freezing on fruits.
Split Fruits are usually caused by uneven watering, such as months of summer heat with minimal or no water followed by heavy fall or winter rain. To eliminate or minimize split fruits, maintain sufficient soil moisture from the time fruits set until they are fully ripe.
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Other articles relating to problems, pests and diseases of citrus:
Harvesting Citrus in the Home Garden: Preharvest Care
Planting Citrus Trees: Proper Planting and Long-Term Health
Protecting Your Citrus Trees: Sunburn and Garden Tools
Citrus Leafminer: Serious Pest or Aesthetic Irritation?