Down & Dirty: Tiny Citrus

Every week we get Down & Dirty, in which Nozlee Samadzadeh breaks down our favorite seasonal fruits, vegetables, and more by the numbers.

Last week, we talked all about citrus, from simple navel oranges to elegant bergamots. Today we're scaling down to talk about a whole range of tiny citruses, from the quotidian (lemons and limes -- what's the difference between them, again?) to the fantastical (calamondins). Pucker up and get ready -- we have so much to cover!

1. Meyer Lemon: Before we get to lemons themselves, let's talk about how dreamy Meyer lemons are. Introduced to the U.S. from Asia in the early 1900s by a man named -- you guessed it -- Frank Meyer, the fruit is a hybrid between a lemon and an orange (most likely a mandarin variety). Then, the impossible happened: in the 1940s and 50s, a citrus virus was found to be growing on almost all Meyer lemon stock in the U.S. Fortunately, some virus-free trees were found and cloned by grafting, and the Texas and California Departments of Agriculture initiated programs to distribute virus-free budwood to their citrus nurseries. The new strain's name was changed to the "Improved Meyer Lemon," and we all lived happily ever after.

Meyer lemons are rounder than the regular kind, with orange-yellow skin that this NPR article describes as "the color of a fresh egg yolk." As a result of hybridization, they have thinner skin and pith, lower acidity, and more sweetness than lemons, which means that the entire fruit is edible! You can use a Meyer lemon anywhere you'd use a regular lemon -- the adventurous can eat them raw like oranges -- although we love to highlight their delicate flavor in macarons, cheesecake, blended whole in a tart, and on focaccia. Meyer lemons store well in the fridge, so stock up while they're in season and enjoy them for months. And for you gardeners: hardy, petite Meyer lemon trees are perfect for warm climates -- or even indoors for cold ones.

2. Lime: Fully ripened limes can be confusing: they're yellow! So why are limes picked when unripe? The answer is in the taste. A lime that has reached its peak size but is still green has that balance of acidity and sweetness that we associate with the fruit. Fully mature yellow limes can develop off-flavors and an unpleasant sour sweetness. (They're still edible, mind you; it's just not what we associate as "lime.") There are many different species of lime, each with unique characteristics:

• Persian Lime: Also known as the Tahiti lime, this is the smallish, green-yellow, seedless lime you're most used to seeing in grocery stores -- it grows well even in dry climates and has a high yield, making it a favorite worldwide.
• Key Lime: Tiny, spherical Mexican key limes turn yellow without flavor loss and have a surprising acidity and juiciness for their size. Because of their tiny size and thorned trees, key limes aren't often commercially available, but they're worth the trouble it takes to find, juice, and zest them.
• Kaffir Lime: Native to Southeast Asia, kaffir limes have knobbly thick skin with intensely, almost inedibly sour juice. The rind and leaves of the kaffir plant are used in curry pastes and soups across Thailand, Vietnam, Malaysia, Indonesia, Burma, and more. You can sometimes find frozen kaffir limes and leaves at Southeast Asian markets.
• Finger Lime: These Australian limes look like fat, squat pickles. Cut them open and they're even more delightful: the vesicles of juice pour out of their membranes like pearly caviar! Lucky Californians can occasionally find these at the farmers' market -- the rest of us have to be content with just photos.

3. Lemon: As acidic citrus goes, lemons are on the more mellow side of things -- it's no surprise they're the most popular tiny citrus around. (We probably don't need to tell you about the amazing recipes you can make with lemon zest, juice, and pulp, but just in case: lemon-basil sherbet, lemon curd, lemon-caper dressing.) The lemons you buy at the grocery store are almost guaranteed to be either Eureka or Lisbon fruit, known for their seedlessness, relatively thin rind, juiciness, and flavor. But keep an eye out for more interesting lemons: there's a Eureka variety with pink flesh (for true pink lemonade!). And in Italy they even name each of the six lemon harvests of the year, with dozens of local varieties from the baseball-sized Femminello Sfusato of the Amalfi coast, used to make limoncello, to the sought-after green Verdellis lemon.

4. Kumquat: Delicate, olive-shaped kumquats are one of the oldest citrus varieties around -- they were grown in China as far back as 1100s! There are ovular and globular varieties, both of which have the extremely thin, sweet skin and sour pulp that characterizes the fruit. While you can just pop whole kumquats as a snack, they're also wonderful in the kitchen: their small size makes them perfect for candying and marmalades, or you can stud them with cloves for a pretty garnish in your apple cider. Kumquats have been hybridized with many other varieties of citrus, which brings us to our next fruit...

5. Calamondin: Most popular in the Philippines, the calamondin is a hybrid of a kumquat and a tangerine. They're used in fruit juices, marinades, and pickles just like other citruses. In general, hybridizing a citrus with a kumquat yields a tiny version of itself. Calamondins, lemonquats, limequats, orangequats, and yuzuquats all share the same characteristics: thin, sweet skin and flesh that's like a more sour version of the second citrus.

And more! there are many more tiny, acidic citruses we couldn't cover today. Here are a few to start:

• Rangpur Lime: Named for the city in Bangladesh in which they were first grown, Rangpur limes are a cross between a mandarin orange and a lemon. So they're not limes at all -- but they do share that sour, bitter acidity (which Florence Fabricant describes as having a "deeply floral, honeysuckle aroma") and can be substituted freely in recipes for curd, marmalade, and cream pie.
• Yuzu: Squat, round, and with yellow-orange skin like a grapefruit, yuzu originated in China and Japan. While its rind can be used just like other citrus zest (in Korea they use it to make marmalade), it's the juice that is traditionally sought after: yuzu is the central ingredient in Japanese Ponzu sauce. You can find bottled yuzu juice in Japanese markets.
• Buddha's Hand Citron: With its irregular octopal sections, this citrus looks more like Cthulhu than a hand. But to each their own! Looks aside, the fruit has little to no juice and is used primarily for its skin (zest, non-bitter pith, and all) which is candied for use in fruit cakes and puddings. Outside the kitchen, the citron also comes in handy as an offering at Buddhist temples.

We've covered so much, but when it comes to cooking with all of these fruits, there's even more to talk about! Lime pickle, preserved lemons, Omani limes…what's your favorite tiny citrus? How do you like to cook with it?

Photos by James Ransom