Kumquat Tree Care: How to Grow Kumquats

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.

This post is sponsored by Fast Growing Trees, a quality source for kumquat trees and many other species.

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Quick Care Guide

Common Name(s)Kumquat, nagami kumquat
Scientific NameCitrus japonica
Germination Time2-4 weeks
Days to Harvest~90 days for fruits to form
LightFull sun
Water:Medium
SoilSandy loam slight clay
FertilizerFrequent
PestsCitrus pests, mealybug, aphids
DiseasesArmillaria root rot, anthracnose, citrus blast

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 8 feet and grow 6 feet wide. They bear yellowish-orange fruits that are oval or round in shape. The fruits can be 1″ in diameter and have a sweet, pulpy skin and slightly acidic inner pulp. 

Despite being citrus trees, the flowering season of kumquats arrives much later. Kumquat tree flowers 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). 

Kumquat Varieties

Citrus japonica harvest
Massive harvest of kumquat fruits from a small section of one tree.

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.

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

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

Planting a Kumquat Tree

Growing a kumquat tree is very easy. Here’s a breakdown of when, where, and how to plant this attractive evergreen tree. 

When to Plant

You can successfully start a new kumquat plant 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.

Where to Plant

Plant in a place where there’s full sun. You can plant them in your backyard or outside on your patio as long as they get well-drained soil. They also do well in pots or containers with suitable drainage holes, but will grow much better if directly planted in the ground. Choose a location where your tree is protected from high wind conditions if possible.

How to Plant

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

After choosing the spot, dig a hole at least 3-5 times wider than the root ball. Carefully place the tree into the hall and ensure that the soil is level with the ground. Tap down the soil for a smooth layer.

Since kumquats need regular hydration, water the plant 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 2-3 inches, while keeping the mulch at least 10 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.

Kumquat Tree Care

Kumquat tree flush with fruit
A kumquat tree full of fruit I harvested from this past summer.

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. 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. 

Sun and Temperature

As mentioned earlier, kumquats are best grown in full sun. They need at least 6-7 hours of sunlight every day for healthy root development, and 8-10 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.

Kumquats do well in USDA hardy zones 9 and 10 and can survive in temperatures as low as 18 degrees F (-7 degrees C). If temperatures drop lower, bring them inside.   

Watering

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 2-3 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 3-4 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’s 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. 

Fertilizing

Apart from the cold winter months, kumquat plants need regular fertilizer. In spring, feed the plant with an all-purpose, slow-release citrus fertilizer. As the plant 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, only on the soil.

Pruning 

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 before the flowering season in spring and after harvesting the fruit. 

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.

Propagating Kumquat Trees

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 plant. 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.

Repotting

When growing kumquat trees in containers repot every 2-3 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. 

Harvesting and Storing

Here’s how you should harvest and store the fruit from kumquat trees. 

Harvesting

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 snips to avoid damaging the plant. You can also trim the fruit along with a small piece of the branch. 

Storing

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 covered paper bags or plastic bags at room temperature. However, it’s best to store the fruit in the fridge. 

Troubleshooting

Even when kumquat trees require lots of care, gardeners don’t face many growing problems.

Growing Problems

After extreme freezing conditions, your kumquat may experience loss of leaves. While they’re hardy down to about 20 degrees Fahrenheit, colder conditions can cause this to happen. 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.

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 or a robust horticultural oil 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 complete death of the plant. Plant your citrus trees with protection from wind, and use a copper-based fungicide to kill off bacteria.

Phytophthora root rot is another issue that may appear. This is usually a fungally-based root rot that is 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? 

Kumquat trees are most often grown in Florida and California. 

Q. What are the benefits of eating kumquat fruits?

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


The Green Thumbs Behind This Article:

Kevin Espiritu
Founder

Lorin Nielsen
Lifetime Gardener

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