I thought it was an orange but then I opened it ….

Oh, I totally get that feeling! Discovering a mystery fruit in your own backyard is both exciting and a little puzzling. Like the original poster, I once thought I knew every plant in my garden, only to be surprised by an unexpected find. You mentioned your fruit is a 'round, orange-colored fruit' with 'light yellow, seedy flesh' once 'cut in half,' and it tastes 'sour with a hint of sweetness.' These are fantastic clues, and they immediately make me think beyond just a regular sweet orange! Let's dive into how we can narrow down what citrus marvel you might have. Many citrus fruits, especially early in their season, can look remarkably similar from the outside. That 'orange-colored' skin could belong to a few different types of fruit, not just a navel or Valencia orange. Key Clues to Identify Your Mystery Citrus: The Skin and Leaves: You described a 'round, orange-colored fruit' nestled among 'green leaves.' Take a closer look at the texture of the skin. Is it smooth, bumpy, or pebbly? Is it thick or thin? Some mandarins have very loose skin, while lemons often have a slightly textured, thicker rind. Also, check the leaves – are they broadly oval like many oranges, or more pointed? Crush a leaf gently; does it have a distinct aroma? This can sometimes give a hint about the specific citrus family. The Inside Story: Flesh and Seeds: Your detail about 'light yellow, seedy flesh' is super important! This immediately steers us away from most common sweet oranges, which typically have orange flesh and often fewer seeds, especially seedless varieties. Lemons: A very strong contender! Many lemons are indeed roundish or oval, turn yellow when ripe (though some stay greenish), and have distinctly sour, yellow, seedy flesh. The 'hint of sweetness' could just be the natural sugars in a ripe lemon, or perhaps it's a less acidic variety. Seville Oranges (Bitter Oranges): These are often mistaken for sweet oranges due to their appearance. They are round, orange, and their flesh is typically yellowish-orange and very seedy and sour – perfect for marmalade! This fits your taste description really well. Some Grapefruit/Pomelo Hybrids: While less common, some varieties can have yellowish flesh and a tart, slightly sweet taste, though they are usually larger. Unripe Oranges: While possible, if the tree has been there for a while and this is its typical taste, it's less likely to be an unripe sweet orange year after year. Taste Profile: "Sour with a hint of sweetness" is the defining characteristic. This clearly points to a tart citrus. If it were a sweet orange, the sourness would be minimal. If it were a lime, it would likely be intensely sour without much sweetness. This balance suggests a lemon, a sour orange, or perhaps a specialty citrus like a Rangpur lime (which looks like a small orange but tastes like a sour mandarin/lemon hybrid). What's Next for Your Tree? Once you have a better idea of what your tree might be, you can start exploring its culinary uses! If it's a lemon, imagine all the lemonades, desserts, and savory dishes you could make. If it's a Seville orange, get ready for some amazing homemade marmalade. Even if it's just a beautiful 'lemon tree aesthetic' in your yard, knowing its identity can help you care for it properly. Have you noticed thorns on the branches? That's another great identifier for many citrus varieties. Regardless of what it turns out to be, having a fruit tree in your garden is such a delight. Keep observing it through the seasons, and perhaps visit a local nursery with a fruit and leaf sample – they are often experts in regional varieties! What are your best guesses, Lemon8 fam? Share your thoughts!