A potted citrus tree would be worthy of window space even if its fruit were inedible. The orange or yellow fruits are quite decorative against the luxuriously green foliage, and the fragrance of the flowers rivals that of gardenia or jasmine. The plants' beauty is attested to by the fact that the citrus most commonly grown as houseplants are the Calamondin and Otaheite orange, both of whose robust-flavored fruits is hardly edible.
The way I figure it, if I'm going to grow a potted citrus, the plant might as well also bear tasty fruit. Oranges or grapefuits are a possibility, although you couldn't hang many of either of these relatively large fruits on a pot-sized plant. And a small orange or grapefuit tree festooned with large fruits would look sort of clumsy. Lemons or limes are good choices, since the juice of only one fruit will flavor a whole bowl of guacomole or a few servings of fish. I get the most out of one citrus plant by growing a type that has more than just lush foliage, fragrant flowers, and edible fruit. I am growing kumquats, whose skins are even edible!
Just about any citrus plants can be started readily from seeds. "Volunteer" orange seedlings used to sprout at the base of a dracaena that lived next to a rocking chair in my living room, evidently from seeds disposed of as someone sat rocking and eating an orange. (How did I know they were orange seedlings? Crushed citrus leaves smell much like the fruit.) Citrus seeds germinate readily if sown fresh, before they dry.
Citrus are fairly unique in that many seed-grown plants bear fruits identical to the plants that bore the fruit from which the seed was taken. That's because their seeds can form solely from mother plant tissue; plants grown from such seeds are genetically identical to the mother plant. So a 'Valencia' orange seedling will eventually bear 'Valencia' orange fruits. Not so for 'MacIntosh' apples or 'Bartlett' pears.
Hold on a minute before you start spitting pits for your citrus orchard. Even under ideal growing conditions, the plants could take years to finally bear. And all the while they are in the juvenile stage, the seedlings are armed with stout, inch-long thorns.
I bought my kumquat plant at a nursery, but if I had known someone with a kumquat plant, I could have started the plant from a cutting. Most citrus root easily, and the cuttings usually flower and fruit early on. I once rooted a lemon cutting that was smothered with a half-dozen blossoms when the plant had only four leaves.
Citrus require no special growing conditions. For best fruit production, the plants need sun, which is why my kumquat now basks at a south window in a cool room. When warm weather settles in the spring, I will move my kumquat outdoors to a site almost in full sun.
I'll end with a confession: My kumquat - all kumquats - really are not botanically citrus. But citrus and kumquat are very closely related, even to the point of freely interbreeding and producing fruits with Dr. Seuss-like names such as limequat and citrangequat. And botany aside, kumquats taste and look very much like little oranges.++
Any gardening questions? Email them to me at firstname.lastname@example.org and I'll try answering them directly or in this column.