Capers are not botanically related to olives, despite their similar culinary roles and Mediterranean origins. The caper plant belongs to the Capparaceae family, commonly known as the Caper family. In contrast, the olive tree is a member of the Oleaceae family. This distinction places them in entirely separate orders of the plant kingdom.
The Caper’s True Identity
The caper is the unopened flower bud of the perennial shrub Capparis spinosa, a plant native to the Mediterranean basin and parts of Asia. This low-mounding, sprawling shrub is characterized by its rounded, fleshy leaves and, in many varieties, sharp, hooked spines at the base of each leaf. The Capparaceae family, to which the caper belongs, is part of the order Brassicales, which also includes the mustard and cabbage families.
Capers are harvested and cured in a brine of salt, vinegar, or both. If the bud is left unpicked, it develops into a fruit known as a caperberry, which is larger and often pickled like an olive. The caper’s unique, pungent flavor comes from the release of caprinic acid, a compound that develops during the curing process.
The Olive Family (Oleaceae)
The olive tree, Olea europaea, is the type species for the Oleaceae family, a group of flowering plants in the order Lamiales. This family is composed mostly of woody plants, including trees, shrubs, and some lianas.
Notable plants in this family include ash trees (Fraxinus), which are valued for their hardwood timber, and several popular ornamental shrubs. These include lilacs (Syringa), jasmines (Jasminum), and forsythias (Forsythia). The olive fruit itself is a drupe, or stone fruit, which is a fleshy fruit with a hard pit, a structure fundamentally different from the caper’s flower bud.
Why the Culinary Confusion Exists
The common misconception about capers and olives stems primarily from their shared preparation and use in Mediterranean cuisine. Both ingredients are typically cured in a salty brine or packed in salt. This curing process imparts a similar briny, tangy, and savory flavor profile, giving both the caper and the olive their characteristic piquant taste.
Capers and olives are often paired together in classic dishes like tapenades, pasta puttanesca, and various antipasti platters. Their similar size and texture, especially when comparing the larger caperberries to small olives, also contribute to the confusion. Ultimately, their culinary function of adding a salty, acidic burst to a dish links them in the minds of many cooks, not any actual botanical relationship.