Citrus seem like such summery fruits. Chilled lemonade and lemon meringue pie are best during warm weather. There are certainly plenty of lemons that ripen randomly throughout the year, and plenty that last for months on their trees. Most limes, some grapefruits and ‘Valencia’ oranges will be around in summer too. Otherwise, most citrus are at their best right about now, through winter.
Mandarin oranges are traditional ingredients of well stuffed Christmas stockings. Where winters are cold and snowy, far from where they grow, they seem contrary to their natural ripening season.
Of all the citrus, they are the most perishable, so are best as they ripen. Their loosely fitting skins, that are so easy to peel, allow them to oxidize and dehydrate more readily than other citrus fruits.
Tangerines are just Mandarin oranges that were developed in North or South America. ‘Rangpur’ limes are actually sour Mandarin oranges that are somewhat less perishable because their skins happen to fit more firmly. Calamondins, which are odd but likely natural hybrids of Mandarin oranges and kumquats, are diminutive tangy fruits that do not last much longer than Mandarin oranges.
‘Bearss’ limes are preferably harvested right as they grow to mature size, but just before they ripen completely. Their flavor mellows as they ripen and yellow. Fortunately, they develop sporadically through an extensive season, so can be available any time fresh limes are desired. Grapefruits can be left intentionally to mellow on their trees after ripening, although this tactic can inhibit bloom.
Otherwise, many citrus fruits can last for more than three months on their trees without consequence. Some improve with mellowing. ‘Meyer’ lemons, which are a hybrid of an orange and a lemon, ripen like richly flavored lemons, and then mellow like very tart oranges. Since citrus fruits stop ripening when harvested, it is advisable to taste one before harvesting too many that are not ready.
Some ripened Mandarin oranges may have slight green blotches. ‘Valencia’ oranges may be slightly yellowish.