Gardeners in even the coldest of climates can grow miniature orange trees indoors as houseplants, and those in hot, tropical regions can grow miniature orange trees outside. Buying a transplant from a nursery will offer you a greater degree of success, but you can grow your own miniature orange from seed, too. Oranges need lots of sun, warm temperatures and the right amount of water to produce blooms and fruit. Indoor, container-grown miniature oranges may never flower or set fruit, but the attractive foliage still makes for an interesting houseplant.
Choose your orange seeds. Kumquats and calamondins are the most well-known miniature oranges, but you can also use the seeds from an orange or other citrus fruit from the grocery store and later prune them into a small, houseplant-friendly size. Use only fresh seeds when growing miniature oranges.
Mix 1 part peat moss with 1 part perlite or sand and fill a small container. A 3-inch-diameter container is more than big enough to start, and you could even use seed-starting flats. You'll transfer the orange tree to a bigger container later as it grows.
Bury the orange seed about an inch below the surface of the soil, or two to three times the length of the seed.
Water the seeds thoroughly and loosely drape clear plastic wrap over the top of the container. Keep the container in an area where the temperature is around 70 degrees Fahrenheit, and keep it away from direct sunlight for now.
Keep the soil evenly moist, but not waterlogged. Unless the air in your house is very dry, you may not need to water the container at all for the first few weeks.
Remove the plastic wrap after the seeds sprout, about three to six weeks after planting.
Slowly move the plant into a sunnier location to acclimate it to bright lights. Eventually your miniature orange tree should be getting at least four hours of direct sunlight every day.
Transplant the orange seedling into a larger container filled with sterilized potting soil after several sets of leaves have formed.
Water as necessary to keep the soil lightly moist. Mist the leaves of indoor plants regularly to keep them clean and glossy.
Feed your indoor miniature orange tree with all-purpose or citrus fertilizer every two to four weeks during the growing season and less often or not at all in the winter. Follow all package instructions when using fertilizer. Miniature oranges grown outside will need fertilizer once every six to 10 weeks during the growing season.
Prune your orange tree in the spring to keep the tree small and compact.
Transfer your orange tree to a slightly bigger container every year in the spring so that it has room to grow. If you live in an area where temperatures never dip below freezing, you may be able to plant your orange tree outdoors. Choose a location with full to part sun.