kumquat (lat. citrus japonicalisten)) is a small evergreen tropical tree of the root family (rutaceae), originally from Asia. It is extremely attractive as a landscape plant, both in the garden and in a large container on the terrace or balcony. This broadleaf plant has glossy dark green leaves and produces olive-sized fruits that resemble miniature oranges.
It is classified as Citrus japonica, thus joining the same genus as oranges and lemons. When ripe, the kumquat fruit has a sweet, edible golden-yellow to reddish-orange skin, and the interior is filled with slightly tart pulp.
Kumquat trees have a moderate growth rate, gaining around 60cm per year. They can grow 2 to 3 m tall and the crown 1.5 to 2.5 m wide. The aromatic white flowers bloom in spring and summer. It is a self-pollinating plant, which means that it does not depend on insects to pollinate it, but can produce fruit on its own.
At first glance, kumquat fruits can be mistaken for small oranges. However, there are some key differences. Kumquats are smaller and oval in shape, 1.5 to 4 cm in size, while oranges are rounder and not as sweet. Also, kumquat husks are edible. The pulp of the fruit has a slightly sour taste, divided into 3 to 8 segments in which, depending on the variety, the seeds are present.
Types of kumquats
While they look like small citrus fruits, they are not. Kumquats are in their own genus and share only one common color with oranges. However, they are often crossed with other citrus to produce various hybrids.
Citrus japonica Nagami
Nagami is the most popular type of kumquat. The fruit is oval in shape and deep orange in color and has 2 to 5 seeds.
Citrus japonica Meiwa
The fruit is larger than the Nagami type and has sweeter pulp and juice, and is almost seedless.
Citrus japonica Marumi
This species is indigenous to Japan. It has a small, round and very juicy fruit with a thick orange-yellow skin.
Variegated Centennial Citrus Japonica
A compact, variegated species that can grow 2 to 3 m tall. It has variegated white and green leaves, and when ripe, the fruit is mottled orange and red.
kumquat cultivation
The kumquat tree, especially the Nagami variety, is relatively easy to grow. However, like other citrus trees, it cannot survive neglect. Originally from Southeast Asia, it has been cultivated in China since the 12th century. Today, the kumquat is grown in California, Florida, Mediterranean countries, Japan, China, Indonesia, Israel, Peru, and Brazil.
coincidence of cultures
The kumquat can benefit greatly from being planted near other citrus trees (orange, lemon, lime, tangerine, grapefruit, pomelo), but each must have enough space for branching. For outdoor planting, you can plant near peas and alfalfa because they release nitrogen into the soil, which kumquat trees love.
Irrigation
Kumquat fruits like soil that is evenly moist, but not soggy. You can check the soil moisture by poking your finger into the soil until the second joint, if it feels dry it’s probably time to water. A 5-7 cm layer of mulch over tree roots can help maintain soil moisture. You just need to make sure that the mulch is at least 7cm away from the trunk of the tree, as moisture retention in the trunk can lead to disease and rot.
Fertilization
It is recommended to wait 2-3 months after planting kumquats before adding citrus fertilizer. Never fertilize the soil in winter.
Spread
The kumquat can be grown from seed or from cuttings of the tree. Propagation by cuttings is done by cutting about 10 cm of branches with at least 3 nodes from the kumquat tree in spring. When cutting, use a sharp, clean garden knife or saw to remove the branch. It is recommended to take several cuttings to ensure that one of them takes root and becomes a tree. Cutting tools should be sanitized with isopropyl alcohol or diluted bleach before and after cutting. The cut end of the branch is soaked in water mixed with rooting hormone for up to 5 days.
To make the correct hormonal solution, it is necessary to carefully follow the instructions on the package. Rooting hormones can be purchased in liquid or powder form at garden stores. In addition, it is possible to dip the end of the cutting in rooting hormone powder and place it directly in the ground. After soaking, the cutting is placed about 1.5 inches deep in a container of moist soil. The cutting is fixed to the ground so that it can stand on its own. The soil should be moist, but not completely wet and sticky. Also, it should not be completely dry. It will take several weeks for the roots to establish before the plant can be moved outdoors and into direct sunlight.
Most, however, choose to purchase grafted trees from nurseries rather than try the propagation technique themselves, as it can be quite tricky.
Transplant
A potting mix designed for cactus or citrus plants is ideal for planting and transplanting kumquats. It needs to be transplanted every 2-3 years to a larger container than the previous one. These plants do not like to be rooted. The best time to transplant is in early spring when the leaves appear.
Rejuvenation
The kumquat tree does not require much thinning and pruning. It is only necessary to remove wilted or damaged branches. Occasional pruning allows more light and airflow at the top of the tree, which aids in future flowering and improves plant health. Also, you need to remove grass and other plants below the canopy that can steal nutrients from the kumquat tree. Do this carefully so as not to damage the roots near the surface.
Land
Kumquat trees prefer moist, well-drained clay soil with a slightly acidic to neutral soil pH, i.e. pH values of 6 to 7. Heavy clay soils are not suitable at all, as this can cause root rot.
air-conditioned
Kumquat trees need a lot of sun and do best with at least 6 to 8 hours of direct sunlight. When grown indoors, it is recommended to place the tree next to a window or place it under artificial grow lights. The kumquat will survive strong, indirect sunlight, but then it will not be productive, meaning it will not bear fruit.
It does not like cold weather, although it can survive temperatures up to 18°C. The ideal humidity level is 50 – 60%. If the tree is grown indoors during the winter when the heat is on and the air is dry, it is necessary to use a humidifier or place the container on a tray filled with gravel and water to raise the humidity level.
planting kumquats
The kumquat is usually planted as a young nursery. You should definitely leave space between the trees when planting – at least 1.5 – 2 m. The planting hole should be 3-5 times as wide as the root ball and about the same depth. A support structure is usually not required.
planting time
The best time to plant kumquats is in spring, after all danger of frost has passed.
Sowing from seeds
To grow kumquats from fruit, you need to harvest the seeds from several mature kumquats and place them in a container of water for several days to separate the seeds from the pulp. When the fruit becomes soft, the pulp is crushed and placed in a bowl of warm water. The pulp and non-viable seeds will rise to the top of the water, while the viable seeds will remain at the bottom. Good seeds are removed from the container and left on a paper towel for about a week to dry.
After that, the kumquat seeds are placed on the surface of moist soil inside a smaller container and then covered with 1/4 inch of coarse sand. To keep the soil warm and moist, the container with the seeds is placed in a clear plastic bag that can be closed securely. Put the pot in the bag in a warm place for germination. The plastic bag will keep the environment moist, but it’s important to check the soil and water it as needed so it doesn’t dry out. Bright light is not necessary at this stage.
When the seeds begin to germinate, the plastic bag is removed and the container is placed in indirect light, where it should normally remain for 2-4 weeks during the germination process. When the seedlings grow to 5-7 cm in height, they should be transplanted into small pots. When the weather warms up enough and the seedlings harden off, they can be transplanted outdoors.
cultivation in the garden
It is necessary to choose a place that receives a lot of sun, that is protected from strong winds and where the soil is well drained. No nearby tall trees should shade the kumquat, as this can affect its growth and fruit production.
greenhouse cultivation
The kumquat can be grown in a greenhouse in a container. This will protect it from the cold in winter, and in summer it can be taken outside to a sunny place.
container farming
In the event that there is no suitable place to plant in the garden, the kumquat thrives very well in a container on balconies or in an enclosed space with sufficient light. The containers can be made of plastic, wood, clay or stone. Planting in the largest container of at least 18 liters is recommended and must have good drainage.
To prevent rotting, the container should have drainage holes in the bottom and should be kept in a place with good air circulation. When cooler temperatures and winter arrive, it is necessary to move the tree indoors. In the spring, the tree can be returned outdoors after night temperatures are consistently above freezing. However, it should definitely harden off with progressively longer exposures outdoors over several weeks before it fully relocates to its permanent sunny spot.
maintenance and care
These trees are easy to grow, but do not tolerate neglect. It needs a lot of attention and care to thrive and produce lots of delicious fruit.
plantation maintenance
An important part of kumquat tree care is to keep the soil around the young trees moist, but not to overwater so the soil doesn’t become sticky. Once the tree is established, it should be watered during dry spells. Fertilizer is withheld for the first 2-3 months during cultivation, and then fertilizer intended for citrus trees is used.
A healthy tree needs 6 to 8 hours of direct sunlight. If grown indoors, they should be moved outside for the summer to produce the best fruit.
slimming
It is not necessary to thin the kumquat tree except to shape it and remove wilted parts of the plant. If certain leaves block the flow of air through the tree, it is essential to thin occasionally to open the flow and ensure flowering.
Circumcision
It is necessary to prune each branch that sprouts below the bud, otherwise it will not bear fruit. Pruning the tree to shape is done after the fruit has been harvested, but before the flowers appear the following spring. Pruning from below is avoided. All citrus trees grow best as bushes so that the entire trunk is shaded by the leaves. In the spring, before the summer heat, withered, damaged and deformed branches are removed.
Harvest
Some varieties of kumquat flower and bear fruit twice a year. New seedlings may need 2 or more years of growth before they bear fruit. By buying larger adult trees, you can get fruits in the first year. Different varieties may have different harvest times. Some bear fruit from November to January, while others from December to April. Kumquats are ripe when their skin is deep orange and the fruit is slightly soft to the touch. Cut the fruit at the stems with a knife or scissors.
Drying
Kumquats can be dried using a food dehydrator or in the oven for 2 hours at 200°C. Dried kumquats can be stored for 6 to 12 months in an airtight container or in the refrigerator in a resealable plastic bag.
To properly dry kumquat, it must first be washed and patted dry with paper towels. Then cut it to the desired thickness. The pulp and seeds can also be squeezed if only the skins are dehydrated. The kumquat slices or shells are placed on the dehydrator tray and dehydrated for about 6 hours at 57°C until the slices are completely dry and crisp.
Alternatively, the kumquat can be dried in the microwave. The study showed that such drying at 900 W significantly shortened the duration of drying compared to drying with hot air and vacuum. The fruit slices dried in 42 minutes. Furthermore, the samples dried in a microwave oven had the highest antioxidant activity.
Storage
Kumquat fruits can be stored at room temperature for only a few days. They do not have a long shelf life because they have a thin and delicate skin. To extend their shelf life, they are best stored in the refrigerator, where they can stay fresh for 2 weeks to a month.
Preparation for the next season
In order for the kumquat tree to overwinter, it is necessary to bring it indoors during the colder months. It can be brought back outdoors in the spring once night temperatures are consistently above freezing.
Diseases
Kumquat trees are susceptible to rot and wilting in poorly drained soil and in areas prone to flooding. Anthracnose is the most common disease you can get.
Anthracnose is a common disease of citrus. This disease manifests itself as leaf spots and can be prevented by spraying the tree three times a year with horticultural oil. If it does occur, most copper-based fungicides will kill it.
pests
Kumquat trees are susceptible to common pests like aphids. Mealybugs are common pests on container-grown kumquat trees.
aphids
Aphids are small yellow, white, or black insects that feed on leaves, slowly killing the plant. During infestation, the leaves turn yellow and fall off the plant. To avoid this problem, it is important to keep the soil well-drained and to avoid excess moisture and too much mulch build-up around the tree. In the event of an infestation, it will help to wash the plant with water, a good insecticidal soap, horticultural oil or neem oil.
flour beetles
Mealybugs are insects that feed on plant sap. They mostly attach to the undersides of leaves, often near the veins and petiole. Container grown kumquats can become targets for these pests. As with most pests, it is recommended to first wash them off the plant with a stream of water or control them with horticultural oil and insecticidal soap.
The use of kumquats
The kumquat fruit contains numerous nutrients, which is why it is used in different ways. It plays an important role in the health of the body. Its consumption improves digestion and the body’s immunity. It is also good for healthy skin and hair.
Kitchen
The kumquat has a sweet skin and a dry, smooth flesh, mostly seedless, so its flavor is not as bitter as other citrus fruits. They can be eaten raw like grapes or sliced as a side to a salad. Although they are most often eaten raw, they can also be used in jams, marmalades, jellies, liqueurs, and in marinades and sauces for meats. They can be eaten pickled, candied and cooked. Kumquat peel is much less bitter than other citrus fruits, making it more palatable to eat. Therefore, dehydrated kumquat husk slices are very tasty to snack on.
Cosmetic products
Kumquat extract contains minerals like calcium and magnesium, as well as vitamins C and E, which boost energy and help maintain skin health. It is used as an ingredient in cosmetics because it reduces wrinkles, prevents loss of skin elasticity and other symptoms of skin aging.
Medicine
It stands out for its rich contribution in vitamin C, which has antioxidant properties, as well as fiber and water. They also contain smaller amounts of B vitamins, vitamin E, iron, magnesium, potassium, copper, and zinc. The edible kumquat seeds and bark provide a small amount of omega-3 fats. Its consumption strengthens the immune system.
Economy
The country of origin, China, remains one of the world’s leading kumquat producers. However, production is also increasing in other Asian countries. The kumquat is grown in California, Florida, Brazil, Peru, Israel and in Mediterranean countries.
Interesting stuff
The kumquat plant originates from southern China. It was described in Chinese literature as early as 1178. European writers mention kumquat in 1646 after visiting China. It was brought to England by the explorer Robert Fortune in 1846, and soon after it arrived in the United States, that is, in 1850.
Kumquat trees are a popular gift for the Chinese Lunar New Year. The plant itself symbolizes prosperity, happiness and wealth.
The English name “kumquat” comes from the Cantonese “kamkwat”, translated as “golden mandarin”.
Photo: Hans Braxmeier / Pixabay