Wow, the debate between whether you can or can not grow Citrus from seed is amazing. I often wonder if the whole debate is so the average person will not try growing their own tree from the grocery store fruit and will be dependent on "Big Citrus" to get their trees and fruit. This is probably a little cynical on my part, but this is what I do know.
The current Florida citrus industry developed from 16th-century Spanish introductions of sour orange, sweet orange, lemon, lime, and citron from either seeds or seedlings. Citrus was spread further by Indians and by pioneers who settled the rivers and lakes of north Florida and the eastern Florida seaboard. Does this mean that all those citrus trees produced bad fruit? I don't think so.
Granted, the amount of time that a citrus tree will produce fruit is much longer than if you grafted one. The average wait time can be anywhere from 2-3 years upwards to 12+ years. The seedling trees will also tend to be very thorny. The biggest debate is whether they will come true to type. In other words, if you plant a good tasting sweet orange will it be the same? According to Dr. Carl Campbell at the University of Florida Extension research center, almost any sweet orange will come true from seed, as well as key limes, grapefruit, tangerine and tangelo. Two varieties that will not come true from seed are the temple orange and pomelo (Grapefruit grandfather). Meyer lemon also falls under this category.
There are some advantages to growing your trees from seed. One obvious advantage is that it is much less labor intensive to simply sow citrus seeds and eliminate the grafting step. Another advantage is that the seedling will most likely be free from viruses that sometimes get into the budwood that is used for grafting large numbers of trees. There has never been an instance where a citrus disease has been proven to have been introduced by seed. My favorite advantage is price! You can buy a great tasting piece of fruit for what, fifty cents to a dollar, depending on time of year? If you get three seeds in it, that equals sixteen to thirty three cents a tree. Now if you compare that to twenty five to forty five dollars per tree, what kind of savings are we talking? It's a no brainer. Of course, this brings us back to the time issue again. Key Limes are your earliest producer from seed, averaging 2-3 years. Your oranges, lemons, Persian limes, tangerines will be in the 5-7 year ballpark. The grapefruit and pomelo will be the longest, taking anywhere from 8-12 years. So patience is most definitely a virtue.
Okay, so you found a fantastic orange that you just have to have more of in the future. It has five seeds in it and you want to try growing it. After extracting seeds, rinse them thoroughly in water and plant them as soon as possible. Citrus seeds do not do well drying out like most seeds, they rapidly lose their viability. You will want to use a good potting mix, keep it damp, not wet. I tell people that you want the consistency of a damp sponge. When planting, place seeds 1/4 to 1/2 inch deep in the pot. Be sure the seeds get enough sunlight, warm soil temperatures, and stay moist. Under ideal conditions, seeds will take about two weeks to germinate.
Like I mentioned, seedling trees will be thorny. If these pose a problem, clip them off with nail clippers. This will not cause any harm to the tree. As the tree gets older, the thorns will stop being a problem.
Now, to be completely truthful, there is always the possibility that the fruit you will get may or may not be the exact same as the fruit you ate. Bees travel great distances to collect pollen. Most citrus that you get in the store have come from very large groves of the same variety. If the fruit you happen to be eating came from the fringe of the grove and a very busy bee was coming from a different grove, there is a slight chance of cross pollination. Even thought there is a book out there, circa 1971, that suggests that if you plant a lemon seed you might get a grapefruit, the chances that you get what you want is pretty good. Besides, there are only three possibilities of what the fruit will taste like.....not as good, as good as, or better than.....two out of three ain't bad!