And how is it different from a regular lime?
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Everybody knows Key lime pie, but most know little to nothing about the citrus fruit behind the famous dessert (outside of the folks in the Florida Keys, of course). So are Key limes any different than the regular limes you find at the grocery store? And can they be substituted for one another? Here you'll find the answers to these questions and more.

What Is a Key Lime? 

A key lime, also known as a Mexican lime or West Indies lime, is a type of hybrid citrus fruit commonly grown in the Florida Keys. They typically measure about one to two inches in diameter. Although they are picked when they're green, they actually begin to turn yellow as they ripen. 

In terms of taste, key limes have a higher acidity, making them a little more tart than what we consider "regular limes." This makes them ideal for pairing with sweeter ingredients, hence the ever-popular Key lime pie. In Mexico, key limes enjoy a year-round season, but in the U.S. (mostly in Florida and California) they only grow between June and September.

Key Limes vs. Regular Limes: What's the Difference?

One regular lime and one key lime on white background
Credit: Andy Lyons/Meredith

To understand the difference between Key limes and "regular limes," we must first understand what we mean by "regular limes." The limes you can find in the grocery year-round, or what we consider conventional limes, are actually called Persian or Tahitian limes — and they're much less common worldwide than Key limes. Who knew?

So how did Florida end up as the de facto Key lime capital? The citrus fruit is actually native to Southeast Asia. From here it traveled through the Middle East to North Africa and eventually made its way to Europe, where Spanish explorers brought it with them to Florida.

Key limes were grown commercially in Florida up until the 1920s, when a hurricane wiped out many groves. Afterwards, farmers opted to replace them with the larger, seedless Persian limes, hence their widespread availability in the U.S. today. 

In terms of physical differences between the two types of limes, Key limes tend to be much smaller than Persian limes. And because of this size difference, it's going to take a lot more Key limes to produce the same amount of juice that comes from Persian limes.

Key limes are also more yellow in color (as yellow indicates ripeness for Key limes), with thinner rinds. They have more seeds than Persian limes, and as we've already established, they're more aromatic and bitter in taste.

Can You Substitute One for the Other?

So, can you make Key lime pie with Persian limes instead of Key limes? After all, their short season doesn't always leave you with much choice. The answer is yes, the two can easily be substituted for one another.

When baked into pie or dessert, it's very hard to tell the difference between the two. However if you're lucky enough to get your hands on some Key limes, make sure to make the most out of them while you can for maximum tartness.

Where to Buy Key Limes

Because Key limes only grow in certain regions of the U.S., they just aren't going to be available in most places. They are also very finicky to ship, making them less than ideal for long-distance transport. Key limes are also significantly more expensive than Persian limes, and they require twice as many limes to produce the same amount of juice as Persian limes. 

So if you live in a region where Key limes are readily available at supermarkets and farmers' markets (looking at you, Floridians), take advantage! But if you don't, you can often find bottled or canned Key lime juice at grocery stores and specialty stores.

key limes surrounding key lime pie
Credit: Kritsada Panichgul/Meredith

How to Use Key Limes

Know this before you get started cooking or baking with Key limes: they're notoriously hard to juice. I would recommend investing in an inexpensive citrus juicer ($18; Zulay Metal Hand Juicer Lemon Squeezer on Amazon) so your hands don't cramp. Squeeze the juice into a fine sieve ($12, Fine Mesh Sieve Strainer at Amazon) to remove any pulp or seeds. 

Now that you're ready to start putting your Key limes to use, I recommend you use them where they really shine: dessert! Key lime pie is an obvious (and excellent) choice, but you may also want to consider some of these different Key lime desserts: White Chocolate Key Lime Endeavor with Macadamia Crunch, Key Lime Cheesecake I, and Key Lime Cake II

If you're looking for something savory, Key lime juice adds the perfect amount of brightness to these dishes: Margarita Shrimp Fajitas, Key West-Style Baked Grouper, and Tropical Mango and Pineapple Paradise Salsa.

How to Store Key Limes

Like Persian limes, you'll want to store Key limes at cool room temperature. Use ripe Key limes within two days. Don't bother putting them in the fridge, as this will only speed up their decay. 

But if you want to preserve their juice, you can pour them into ice cube trays ($8; Ice Cube Trays at Amazon) and flash freeze them before transferring them to a freezer safe bag and storing for up to six months.