Answer: Most citrus grown in Arizona is grafted on to a hardy rootstock. So in selecting a citrus tree to plant, you choose the type of fruiting wood (Minneola Tangelo, Ruby Red Grapefruit, etc.) and you select the rootstock upon which it is grafted (sour orange, Carrizo, etc.). The rootstock protects the fruiting wood from pathogens in the soil.
When you plant the seed from a fruit of an orange, you are planting fruiting wood, which may not be well adapted to our soils and pests so it may not live long and prosper in our environment. For these reasons I discourage you from trying to grow an orange tree from seed if you are looking for a long-lived tree with quality fruit.
All that said, it can be a great exercise for your children to see the process of harvesting seeds from the fruit and watching the plant grow. Plant the seeds as soon as possible after removing them from the fruit. Do not allow them to dry out. The seedlings can be grown in beds and transplanted into pots or rows during the spring, after frost danger is past.
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