Planting an Orange Seed
Understand the problems with growing from a seed. An orange tree grown from seed will be more vulnerable to disease, and its oranges may not taste like the fruit the seed came from. The tree could also take between four and fifteen years to bear fruit for the first time. A young tree purchased from the nursery is actually a combination of two plants: one tree bred for healthy roots and other attributes, plus branches of another tree grafted onto the first. These branches come from a tree that produces high quality fruit, and because they are already mature, the tree should produce fruit within a year or two after purchase. All that explained, feel free to continue with these steps if you're up for a challenge.
Select seeds before they have dried out. Cut open an orange carefully without breaking the seeds inside, or simply use the seeds that aren't damaged by the knife. Pick out seeds without any dents or discolorations. Seeds that appear withered and dry, usually after they've been left out of the fruit for too long, have a lower chance of growing. Note that some varieties of orange are seedless. Ask a fruit seller for a variety with seeds.
Wash the seeds. Hold the seeds under running water and gently rub off any pulp or other material that has gathered onto the seeds. Be careful not to damage the seeds, especially if some are already beginning to sprout. There is no need to dry the seeds afterwards. Keeping them moist will make them more likely to sprout.
Get the seeds to sprout faster by keeping them moist. Assuming you're using seeds that haven't yet begun to germinate (sprout), you can shorten the time it takes to reach that point by keeping them in a moist environment. You could keep damp seeds in a plastic bag in the refrigerator for 30 days before planting, or simply keep the soil they're planted in moist, but not soggy. If you are using seeds that have dried out, they are in a dormant state and can take months to germinate, or fail to do so at all. Professional orange growers soak some slow-germinating orange varieties in gibberellic acid before planting to speed up the germination even more. This is typically unnecessary for a home project involving a handful of seeds, and can easily backfire if the wrong amount is used for your orange variety.
Plant each seed in a small pot of well-draining potting mix or soil. Plant them about 1/2 inch (1.2cm) beneath the surface. Orange trees aren't too picky about which potting mix you pick, but it is important that water does not pool around the seeds (and later roots) and cause rot. Water should drain through the pot quickly when you water the soil. Optionally, you can purchase citrus potting compost to add to the mix, which will increase its ability to hold nutrients and create the more acidic (low pH) environment that citrus trees thrive in. Remember to put a plate or other object underneath the pot to catch the draining water. If the soil is poor at draining, mix in hardwood bark chips. This makes the soil less compact, which lets water drain through faster.
Keep the soil in full sunlight. Whether indoors or outdoors, the soil does best at temperatures between 75º and 85ºF (24º–29ºC). Sunlight is the best way to warm your soil to the correct level, since a radiator could dry out the soil too quickly. If you live in a cold or low-sun region, you may need to keep your orange tree in a heated greenhouse or conservatory, even before it's germinated.
Add a balanced fertilizer once every two weeks (optional). If you'd like to speed up the tree's growth, adding a small amount of fertilizer to the soil every 10–14 days will help. To get the best results, you would need to tailor your choice of fertilizer to the level of nutrients in your soil, which should be on the label of the potting soil if you purchased it. Otherwise, choose a balanced fertilizer with relatively even amounts of nutrients. Stop adding fertilizer once the plant has grown into a young tree. Follow the instructions for a Seedling or Young Tree instead. It shouldn't need additional fertilizing until its second year.
Remove the weakest of the three sprouts when the seeds sprout. Citrus seeds have the unusual ability to produce exact clones of the mother plant, called nu-cellar seedlings. These are typically the two fastest-growing sprouts, while a third "genetic" offspring tends to be smaller and slower-growing. Cut off this weak third sprout in order to produce a tree with the consistent quality the parent was bred for.
Caring for a Seedling or Young Tree
Plant the tree into a pot slightly larger than its roots whenever necessary. Whether you just purchased a tree or have been growing it for years, you should plant it in a container that the roots easily and comfortably fit into, but not into one far larger than the root ball. The best time to re-pot your orange tree is in the spring, before it has put a lot of energy into growing. Cut off any dead or broken roots before planting. First sterilize the knife by boiling it or rubbing it with alcohol to reduce the chance of transmitting disease to the tree. Pack the soil gently around the roots to remove pockets of air. The top roots should end up just under the surface of the soil.
Consider an outdoor location. Oranges can grow in USDA hardiness zones 8 through 10 (with minimum annual temperatures of 10 to 40ºF / -12 to 4.4ºC). If you live in one of these warm climates, you may be able to find a place to plant the tree outside: Choose an area protected from the wind. To allow for root growth, plant standard-sized orange trees at least 12 feet (3.7 m) (3.7m) from walls and other large obstacles, and 25 feet (7.6 m) from other trees. If using dwarf orange trees, look up your variety's requirements. The trunk itself can grow to be 10 feet (3m) wide. Plant the tree at least 5 feet (1.5m) from foot paths to keep them clear.
Plant outdoor trees in existing soil. When planting orange trees outside, dig a hole just deep enough to cover the roots. Cover the roots with the soil you just dug out. Potting mixes tend to hold too much water for orange trees, which can lead to rot. Do not cover the trunk with soil, or the orange tree could die.
Keep your tree in full sun and warm temperature. Keep an eye on young seedlings, since they are always more vulnerable to burning or other dangers than established plants, but orange trees should do best in full sun. The best temperatures for orange trees are between 75ºand 90ºF (24–32ºC). They will do poorly in spring or summer temperatures below 45ºF (7ºC), and depending on variety might die in temperatures of 32ºF (0ºC) or below. Sustained temperatures above 100ºF (38ºC) for several days will likely cause leaf damage. If your adult tree is exposed to too high temperatures, hang a sun shade or sheet over the tree until the temperature decreases below 100ºF (38ºC). Move your orange tree indoors before a frost occurs. Citrus trees are more vulnerable to frost than heat, although some varieties may be able to survive a mild period of frost.
Water the plant with infrequently but heavily. Orange trees, once grown into young trees rather than sprouts, prefer to be in soil that dries out before being watered again. Wait until the soil feels dry when you make a deep hole with your finger, then water heavily until the soil is soaked. A large adult plant should be left alone until the soil is dry to 6 inches (15 cm) beneath the surface. Typically, the tree can be watered once to twice a week, but this varies depending on temperature, humidity, and amount of sunlight received. Use your judgement and water more regularly during hot, dry seasons, although you should generally avoid watering plants while the sun is high in the sky. If your tap water is hard (mineral-heavy, leaving white scale on kettles or pipes), use filtered water or rainwater instead to water orange trees.
Fertilize carefully according to age. Adding fertilizer or manure at the right time gives the trees all the nutrients they require to grow and produce fruit, but incorrect use can burn the tree or cause other damage. Use a special citrus tree fertilizer, or any fertilizer that is especially high in nitrogen. Follow these instructions for applying fertilizer or compost: Young trees 2–3 years old should have two tablespoons (30mL) of nitrogen-high fertilizer spread under the tree 3 or 4 times a year, immediately before watering. Alternatively, mix one gallon (4L) of high quality composted manure into the soil, but only in the fall when rains can wash away excess salts before they cause damage. Adult trees 4 years or older grown outside require 1–1.5 lb. (0.45–0.68 kg) of nitrogen a year. Your fertilizer should say what percentage of nitrogen it contains, which will allow you to calculate how much fertilizer you need to use to achieve the correct amount of nitrogen. Scatter over the root area of the tree and water into the soil, either annually during the winter or in three equal batches in February, July, and September.
Remove dust from indoor plants regularly. Dust or grime buildup on a plant's leaves can prevent it from photosynthesizing, which is part of how it gains energy. Brush or rinse the leaves every few weeks if the plant is kept indoors.
Understand that pruning is rarely required. Unlike some varieties of trees, orange and other citrus will do fine without pruning. Only remove completely dead branches, and suckers near the base that look especially unhealthy. You may prune your tree to shape its direction of growth and keep it short enough to pick all the fruit, but only remove heavy branches during winter months to avoid sunburning the exposed inner tree.
Troubleshooting
Protect burned or withered trees by wrapping the trunk in newspaper. If your tree is still young and has just been planted outdoors, it may be especially vulnerable to sunburn. Tie newspaper loosely around the trunk and large branches if you see signs of sun damage, or are living in an area with strong sun.
Test soil pH if the leaves are turning yellow. Yellow leaves may be a sign of alkalinity, or too much base salt in the tree. Test your soil pH to confirm this. If the soil is too alkaline, apply an acidic (low pH) fertilizer and heavily wash the soil to leach out alkaline salts. Too much manure fertilizer, or manure applied during the dry season, can be a cause of alkalinity.
Wash off aphids with soapy water. Aphids are small green pests that feed on many types of plants. If you see them on your orange tree, wash them off with soapy water. Many other solutions are detailed in the Get Rid of Aphids article if this does not work.
Get rid of ants and other pests feeding on the tree. Ants can be difficult to eradicate, but placing the pot in a larger container of standing water makes it impossible for them to get to it. Use pesticides sparingly and as a last resort, especially if the tree is bearing fruit.
Insulate trees that will be exposed to frost. If possible, young trees should be brought indoors before the frost. However, if they are planted outside and you have no space indoors, you should wrap the trunks with cardboard, corn stalks, fleece, or other insulating material. Cover the trunk all the way up to the main branches. Healthy adult orange trees will rarely die due to frost, but they can experience leaf damage. Wait until spring to see which branches survive before pruning the dead ones off.
Encourage fruit growth next year by picking all the ripe fruit this year. Leaving fruit on the tree may reduce the amount the tree produces next year, although if you are only using fruit for home purposes an adult tree should produce more than you need. Some varieties, such as mandarins and Valencia oranges, alternate years of heavy production with years of light production. Fertilize less during the year leading up to light production, since the tree has lower nutrient needs.
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