How to Plant, Grow, and Care for a Kumquat Tree

Kumquat tree, also known as Citrus japonica, is an easy-to-grow fruit tree. From all the citrus trees, this one is the most beautiful with dark-green, glossy leaves. It’s known for its bright orange fruits, which are deliciously tart and sweet.

These trees, native to eastern Asia, are relatively small and beautiful. If you’re looking to grow them in your backyard, you’ll need to know all the care tips! Keep reading for tons of info.

Plant Overview

• Plant Fruit tree
• Family Rutaceae
• Genus Citrus
• Species Citrus japonica
• Native Area Southeast China and Japan
• Exposure Full sun
• Height 8′
• Watering Requirements Moderate
• Pests & Diseases Citrus pests, mealybug, aphids, armillaria root rot, anthracnose, citrus blast
• Maintenance Low
• Soil Type Well-draining, sandy, loam
• Hardiness Zone 9-10

What is a Kumquat Tree?

Kumquat plants have thornless branches and extremely glossy leaves. They bear dainty white flowers that occur in clusters or individually inside the leaf axils. The plants can reach a height of up to eight feet and grow six feet wide. They bear yellowish-orange fruits that are oval or round in shape. The fruits can be one inch in diameter and have a sweet, pulpy skin and slightly acidic inner pulp. 

Native Area

The ‘japonica’ in Citrus japonica gives away its origins somewhat as coming from Japan, but they are actually native to southeastern Asia, particularly regions of China, where it has been cultivated for centuries. It is believed to have originated in areas with subtropical climates, such as southern China and possibly parts of Malaysia and the Philippines. The tree was later introduced to Japan, where it became popular and further cultivated, eventually spreading to Europe and North America in the 19th century, and named japonica.

Characteristics

Despite being citrus trees, the flowering season of kumquats arrives much later. Kumquat trees flower in late spring into early summer. It is an easy-to-care, cold-hardy plant that can tolerate temperatures as low as 18°F (-7°C). 

Whichever you choose, kumquat trees produce round, oval, and bell-shaped fruit. ‘Nagami’ kumquats, which are the most popular, have oblong, juicy fruits that can be eaten whole or used to make marmalades. 

All the kumquat tree varieties are self-pollinating, so you only need to grow one tree. The trees require moist soil, so they need ample water to prevent drying of roots. Kumquats can tolerate both frigid and hot temperatures.

Varieties

Botanically, many of the varieties of kumquats are classified as their own species, rather than a cultivar:

• ‘Nagami’ : The most popular variety, also known as oval kumquat.
• ‘Meiwa’: Large round kumquat, a hybrid of ‘Nagami’ and ‘Marumi’.
• ‘Marumi’: Round kumquat, a bit spicier in flavor than ‘Nagami’.
• ‘Hong Kong’: A native version, often growing in hilly or mountain regions of China.
• ‘Fukushu’: This versatile beauty is perfect for container gardening, making it an excellent choice for small spaces and urban dwellers. You buy this variety directly from the Epic shop as a live plant.

Planting

Growing a kumquat tree is very easy. You can successfully start a new kumquat by planting the seed in spring. Spring is the ideal time for kumquats as the temperature is pleasant with higher chances of rain and, of course, lots of sunshine. Early spring is also the best time to transplant a sapling kumquat.

Set it in a place where there’s full sun. They also do well in pots or containers with suitable drainage holes, but will grow much better if directly planted in the ground.

It’s better to purchase a kumquat tree from a local nursery. Kumquat can sprout from seed, but the resulting tree is mostly weak. Choose a sunny spot and grow the tree in spring to ensure that the kumquat is well-established before winter arrives.

After choosing the spot, dig a hole at least three to five times wider than the root ball. Carefully place the tree into the hole and ensure that the soil is level with the ground. Tap down the soil for a smooth layer. Since kumquats need regular hydration, water thoroughly and don’t let the soil become dry. Mist often, at least a few times a week, until the tree establishes.

Add organic mulch to the surrounding area, about two to three inches, keeping the mulch at least ten inches from the trunk. Ensure proper watering and soil conditions for about a month, and then fertilize. You can use a high-quality citrus formula to do this.

Kumquat tree, particularly the variety known as ‘Nagami’ kumquat, is relatively easy to grow. However, like other citrus trees, it can’t survive on neglect. When you’re planting the tree, it’s essential to treat it with a lot of care.

How to Grow

The journey is extremely rewarding once the kumquat tree begins to bear delicious citrus fruit. Here’s a breakdown of how to nurture and look after it. 

Light

As mentioned earlier, kumquats are best grown in full sun. They need at least six to seven hours of sunlight every day for healthy root development, and eight to ten hours is better. If you’re growing them indoors, make sure to keep them near a window for maximum sunlight, or provide a grow light to keep them healthy.

Water

The key to growing any citrus fruit tree is proper watering. If you’re growing kumquats in pots, the soil needs to be moist but not wet. For this, you must ensure the container has suitable drainage holes and that the soil itself drains excess water away. 

Kumquats need regular watering, especially when the plants are young – you’ll often water two to three times a week throughout the first year. However, make sure not to overdo it for older trees.

To check for hydration, stick your finger at least three to four inches in the soil; if you feel dampness, wait until the soil dries out a little to water again. However, if it’s dry, water the tree until water begins to run out from the bottom of the pot. Trees planted directly in the soil should be watered until the soil is moist, but not muddy. A soaker hose can help.

Soil

Kumquat tree survives well in almost any soil pH. But it can’t survive really sticky, clay-like soils that don’t drain readily. Ensure your soil easily drains away water. If you’re growing in a container, a citrus potting blend is great. Those growing directly in the ground should do a drainage test first.

To do a drainage test, dig a hole at least a foot deep and fill it with water. If it empties out within about 20 minutes, your soil’s perfect. If the water stays in the hole for over an hour, it may be best to work through some compost or other drainage aid. Even a small amount of sand can improve drainage, but perlite is another good option. 

Temperature

Kumquats do well in USDA hardy zones 9 and 10 and can survive in temperatures as low as 18°F. If temperatures drop below, bring them inside. While they can survive these conditions, they won’t do as well if they’re overexposed to cold.

Fertilizing

Apart from the cold winter months, kumquats need regular fertilizer. In spring, feed with an all-purpose, slow-release citrus fertilizer. As it grows, give it diluted liquid fertilizer, like fish emulsion or liquid kelp, on an occasional basis. Always water well before applying liquid fertilizers. Avoid getting fertilizer on the tree itself, aiming only at the surrounding soil.

Maintenance

Kumquat tree doesn’t require much pruning except when you have to remove dead or damaged branches that may be sucking up the tree’s resources. If you want to shape the tree, make sure to do so in winter before the spring flowering season and after harvesting the fruit. 

Carry out an occasional pruning to open up the canopy can allow more light and airflow into the upper part of the tree. This helps with future flowering and reduces the chance of diseases taking hold.

When growing kumquat trees in containers repot every two to three years in containers that are at least a few inches bigger than the previous one. The ideal time for repotting is the early part of the leaf-growing stage in spring. 

Propagating

The trees aren’t generally grown from seeds, although they can be. The tricky part about seeds is that you won’t necessarily get an exact clone of their parent. If you’re trying to raise a particular cultivar, it’s best to go with another method.

Propagate instead by grafting young branches onto the rootstocks of grapefruits and oranges.  The root systems of most grapefruit and orange trees are typically more resilient to fungal diseases in the soil.

Harvesting

Here’s how you should harvest and store the fruit from kumquat trees. Large harvests often result even from small trees!

The harvesting time for most varieties begins from November through January, while for others, it’s from December to April. The fruit is ripe when it’s slightly soft and deep orange. Pick the fruit using scissors or pruning shears to avoid damaging the tree. You can also trim the fruit along with a small piece of the branch. 

Storage

Kumquat fruits don’t have a long shelf life because they have thin, delicate peels. If you want to store them for a week or so, keep them in fully closed paper bags or plastic bags at room temperature. However, it’s best to store the fruit in the fridge. 

Common Problems

Even when kumquat trees require lots of care, gardeners don’t face many growing problems. Here are a few to look out for.

Growing Problems

After extreme freezing conditions, your kumquat may lose leaves. While they’re hardy down to about 20°F, colder conditions can cause this. Try to keep your tree protected from excess cold whenever possible. Drastic changes in light can also cause leaf drop.

Container-grown kumquats can experience twig dieback and loss of leaves if they become rootbound. Try to prevent this problem by ensuring that the pot’s large enough to satisfy your tree’s needs. Repot the tree every few years.

Pests

Kumquat trees are susceptible to mealybug infestations, leaf miners, citrus scale, and aphids. Keep the soil well-drained and avoid excess moisture and piling too much mulch around the tree. A good insecticidal soap, robust horticultural oil spray, or neem oil will help combat the infestation.  

Diseases

Anthracnose is a common citrus disease. This leaf spot disease can be prevented by spraying the tree three times annually with horticultural oil. If it appears, most copper-based fungicides will clear it up. You may also encounter alternaria leaf spots, and those should be handled similarly to anthracnose.

Citrus blast is a bacterial infection that spreads in parts of the US after wind-driven rain. The bacteria, Pseudomonas syringae, enters into the plant via points of damage from the wind. It causes withering of leaves and can lead to the complete death of the tree. Plant your citrus trees with protection from wind.

Phytophthora root rot is another issue that may appear. This is usually a fungally based root rot caused by overly soggy soil conditions. Do not overwater your trees, and you should not encounter this problem.

Frequently Asked Questions

Q: Where do kumquats grow in the USA? 

A: Kumquat trees are most often grown in Florida and California. You can grow them in a warm greenhouse anywhere, though.

Q: What are the benefits of eating kumquat fruits?

A: Kumquat fruits are incredibly high in vitamin C and fiber. Eating them can help strengthen the immune system and support weight loss.

Q: How long does it take for a kumquat tree to bear fruit?

A: On a mature enough tree, kumquats form in about 90 days.

Q: Do you need two kumquat trees to produce fruit?

A: No. Kumquat trees are self-pollinating.

Q: Are kumquat trees easy to grow?

A: Compared to other citrus trees, they are! As long as they have well-draining soil, full sun, fertilizer, and heat, they’ll take off.

Q: What month do you harvest kumquats?

A: They’ll mature between November and April depending on the variety you choose. It’s during this time you can harvest them.

Q: Do kumquats grow well in pots?

A: They certainly do! This is what makes them a premiere citrus for a lot of gardeners.

Q: Can kumquat survive winter?

A: While they may not do well outdoors in winter, as long as they are protected indoors in cold they will be just fine.