Calamondin

Yes. The fruit known as calamansi in the Philippines is the same citrus hybrid botanists call calamondin (× Citrofortunella microcarpa). It is a cross between a mandarin and a kumquat. Calamansi is by far the more common name in Filipino cooking and commerce.

Yes, calamondin is notably more cold-tolerant than most commercial citrus, owing in part to its kumquat parentage. It can survive light freezes and is grown outdoors as far north as the coastal southeastern United States and parts of the Mediterranean. This hardiness also makes it a popular potted plant in cooler climates.

Calamansi juice is a staple souring agent in Filipino cuisine, used in marinades such as poultry adobo, in dipping sauces (sawsawan) combined with soy sauce and chili, and in drinks sweetened with sugar. Its small size and tart flavor make it function much like lemon or lime in Western kitchens. Bottled calamansi juice and frozen concentrate are widely sold in Filipino grocery stores worldwide.

Yes, the thin peel of calamondin is sweet, while the pulp inside is sour, a trait inherited from its kumquat parent. Eaters often squeeze the entire fruit into their mouth to combine the two flavors. The peel is also sometimes candied or used to flavor vinegar-based condiments.