Kumquat trees are the most cold-hardy of the citrus family. Some varieties can endure temperatures down to 10 degrees F, but they do require a hot summer. Believed to have originated in China, the kumquat tree is generally grown in Florida, California and Texas. The kumquat tree provides a fruit that can be eaten raw or preserved in sugar syrup. It is a shrubby, slow-growing tree that is 8 to 15 feet tall. The most common kumquat species with edible fruits are Meiwa, Hong Kong, Nagami and Marumi. The fruit is usually harvested in January. In USDA Zones 8 to 11, kumquat trees can grow outdoors in the ground. If you live in Zones 4 to 11, kumquat trees need to be grown in a pot as a patio plant and moved indoors during the cold winter months. Because kumquat trees are drought-tolerant and pest-resistant, they are rather easy to plant and grow.
Planting in the Ground Outdoors
Plant your healthy, young kumquat tree in the ground if you live in Zones 8 to 11. Add Mycorrhizal fungi to the soil at the time of planting to enable your kumquat tree to access more of the nutrients in the soil and to maximize fruit production.
Place some iron tablets in the ground around the tree if your soil’s pH level is greater than 7.0. This will prevent iron deficiency.
Plant your kumquat trees in full or partial sun, approximately 8 to 10 feet apart. Kumquat trees will adapt to many different well-drained soils. The Nagami kumquat does well in sandy soils, however.
Keep the ground clear of weeds about 3 feet around the tree.
Planting in a Container
Plant your kumquat tree in a container if you live in Zones 4 to 11. Use a sand-based potting mix. Make sure you use a large enough container to give your kumquat tree room to grow and a container that has adequate drainage holes.
Put a layer of gravel on the bottom of the container to help provide good drainage. Allow the top 1-inch of soil to dry before watering your tree and avoid over-watering.
Place the container in bright sunlight, preferably in a window with southern exposure. You can place your kumquat tree outdoors in a sunny spot during the warmer summer months.