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Why Do Most Lemons Have Seeds, While Most Limes Do Not?

Lemons and limes are both citrus fruits, and their juice and zest are often used interchangeably in recipes. So why do lemons (and most fruits) have seeds while limes don’t?

The majority of limes sold in the U.S. are Persian limes (Citrus latifolia). While often thought to be its own species, the Los Angeles Times says this fruit is “a natural hybrid of true lime and citron.” Also called Tahiti or Bearss limes, these limes are parthenocarpic, meaning they’re produced without fertilization and are thus seedless. On the other hand, true limes (Citrus aurantifolia, but known commonly as Mexican, Key, or West Indian limes) do have seeds. Because Persian limes are bigger, have a thicker skin, and are more resistant to diseases than true limes, Persian limes have a longer shelf life. But where do they come from if they don’t have seeds?

Speaking to Scientific American, two biologists at Brookhaven National Laboratory explain that normal fruit starts to develop when a flower’s egg cell is fertilized by pollen. Parthenocarpic fruit, in contrast, develops without fertilization. Fruit can be parthenocarpic for a variety of reasons, such as problems with the eggs or sperm, problems with pollination, or chromosomal imbalances.

Seedless or “large-fruited” limes have three sets of chromosomes rather than two. While some parthenocarpic fruits occur naturally, this genetic abnormality makes wild reproduction extremely rare for Persian limes. To overcome this, farmers use a technique called grafting, where part of a seedless lime tree is removed and inserted into a new tree. This essentially clones the original tree, ensuring that more seedless limes will be produced. (Farmers can also use grafting to fix fruit trees that have been injured.) Grafting allows farmers to produce seedless fruits on a commercial scale.

While most limes you see in the supermarket are probably seedless, some varieties of lime do indeed have seeds. And although most lemons have seeds, some lemons are actually seedless. You may find an occasional seed even in “seedless” lemons due to cross-pollination if the lemons were grown near other fruits. Lemons without seeds are more difficult to find in grocery stores than regular ones, just as limes with seeds are harder to find in stores than their seedless counterparts.

The answer lies in their chromosomal makeup.

Growing Lime Trees From Seed

In addition to nursery-grown plants, grafting is probably your best bet when growing lime trees. However, most citrus seeds are relatively easy to grow, including those from limes. While it’s possible to grow a lime tree from seed, don’t expect to see any fruit right away. The downside to growing lime trees from seed is that it can take anywhere from four to ten years before they produce fruit, if at all.

Growing Lime Trees from Seed

Since many lime seeds are obtained from purchased fruit, they’re most likely hybrids. Therefore, planting lime seeds from these fruits often will not produce identical limes. Polyembryonic seeds, or true seeds, will generally produce identical plants, however. These can normally be purchased from reputable nurseries specializing in citrus trees.

Keep in mind that other contributing factors, like climate and soil, also affect the overall production and taste of lime tree fruit.

How to Plant a Lime Seed

There are a couple of ways to grow a lime tree from seed and knowing how to plant a lime seed is important for success. You can plant the seed directly in a pot of soil or place it in a plastic bag. Before planting lime seeds, however, be sure to wash them and you may even want to allow them to dry for a couple days, then plant them as soon as possible. Plant seeds about ¼ to ½ inch deep in containers with well-draining soil.

Likewise, you can put seeds in a plastic baggie along with some moist soil. Regardless of the method you choose, keep the seeds moist (not soggy) and place them in a warm, sunny location. Germination usually occurs within a couple of weeks. Once seedlings have reached about 6 inches tall, they can be gently lifted and placed in individual pots. Be sure to provide winter protection, as lime trees are very cold sensitive.

If you don’t want to wait so long for lime fruit production, you may want to consider other means of growing lime trees, which will usually bear fruit within three years. However, growing lime trees from seed is an easy and fun alternative to experiment with, keeping in mind that as Forrest Gump would say, “like a box of chocolates, you never know what you’re gonna get.”

In addition to nursery-grown plants, grafting is probably your best bet when growing lime trees. However, most citrus seeds are relatively easy to grow, including those from limes. Learn more in this article.