Kumquat trees are native to China and, like all citrus trees, they prefer tropical to subtropical weather. If you grow them in the ground, most varieties are only hardy through USDA zones 8 to 11. If you grow kumquat trees in a container, however, some varieties can handle zone 4. Unlike other citrus fruit, kumquats are eaten whole, skin and all. They make an interesting treat for your family and friends. Plus, growing kumquat trees is easy compared with growing other types of citrus. Plan to plant your kumquat tree in the spring.
Choose a spot for your kumquat tree. If you are planting it outside, be sure it will be in full sun and protected from harsh winds and cold. Plant on the south side of a house near a wall, if possible. If planting a kumquat tree in a container, make sure you can move the container if needed.
Kumquat trees like sandy loam that is well-drained. If your soil is too claylike, mix sand into it to a depth of about 4 feet to improve it.
Dig a hole about 2 to 3 feet deep and 2 feet in diameter, large enough to accommodate the root ball, if planting the tree outside. Place the kumquat tree in the hole and fill halfway with soil. Water the tree and wait for the water to soak in, then finish filling the hole with soil. Pat the soil down firmly. If you are planting your kumquat tree in a container, use a sand-based potting mix and a container with good drainage. Place a base of potting soil in the container, then place the tree in the container. Fill it with soil and water immediately.
Water your kumquat tree regularly. Water it once a week for about 10 minutes each watering. If your kumquat is in a container, make sure the soil on top does not dry out between waterings.
Fertilize your kumquat tree every summer with a nitrogen-rich fertilizer. If possible, buy a fertilizer specially made for citrus trees. Apply the fertilizer to the base of the tree and water well. For container-grown kumquat trees, place the fertilizer pellets in the container and water well. Apply about 1 cup of fertilizer for each year old the tree is. Once the tree is 3 years old, apply only 3 cups of fertilizer from then on.
Prune your kumquat tree while it is dormant. Remove any suckers at the base. Prune your kumquat tree into any shape you desire. No other pruning is needed.
Protect your kumquat tree from cold weather. If the tree is planted outside, wrap it in blankets if the weather gets down to freezing. If your kumquat tree is in a container, bring it inside when the weather dips below freezing and put it back outside once it warms again.