The kumquat, also known as the Chinese mandarin, is a small fruit tree, ideal for being cultivated in a domestic environment. Its small size makes it suitable for container cultivation. It has a great ability to withstand the harsh weather conditions of winter months. It can be easily cultivated even by those less experienced. Moreover, being less delicate compared to other citrus fruits, it can be planted anywhere, not just in the southern regions. Despite its size, it proves to be very productive; indeed, a few plants are enough to yield a lot of fruit.
Several varieties fall under the name of kumquat, which we will illustrate in this article to give you the opportunity to choose the one you prefer. However, let’s first see what minimal precautions to consider for cultivating kumquats in containers.
Botanical Identification of Kumquat
The kumquat (Citrus japonica) belongs to the botanical family of Rutaceae, which includes citrus fruits. The classification in the Citrus genus is attributed to the Swedish entomologist Carl Peter Thunberg, towards the end of the 1700s. In 1915, the American botanist Walter Swingle reclassified the kumquat into its separate genus, Fortunella, in honor of the British explorer Robert Fortune. The genus Fortunella included several separate species of kumquat. Among these, the most important are: F. japonica, F. margarita, F. Hindsii. However, recent studies have questioned this classification and separation from the Citrus genus. Therefore, there has been a return to the past, and the individual species mentioned above have been downgraded to mere varieties of Citrus japonica.
Botanical Characteristics of Kumquat
A distinguishing feature of the kumquat, setting it apart from other citrus fruits, is that even the peel is often edible. The fruit, being small, is consumed whole. It’s very pleasing to the taste, leaving a dual sensation on the palate—sweetness from the peel and tanginess from the pulp. Moreover, there are few seeds inside, not very hard. Typically, the fruits ripen from October to February and have the ability to persist for a long time on the tree, making it possible to harvest them as needed.
Now, let’s explore the botanical characteristics of the different kumquat varieties. The main difference between one variety and another lies primarily in the shape of the fruits. Here, we’ll limit the description to the varieties mostly cultivated in our latitudes.
The Oval Kumquat, Fortunella margarita, is the true Chinese mandarin, also known as Nagami. It originates from southern China and has been cultivated since ancient times. This kumquat variety gives rise to small, bushy plants. The branches are somewhat spiny, and the growth is dense and compact. Overall, the plant does not exceed two meters in height when grown in a container, and three meters when in open soil. The leaves are lanceolate in shape, shiny dark green on the upper side, and light green on the underside. The flowers are grouped in small inflorescences, mostly blooming in the summer. The fruits, kumquats, are entirely edible, small in size, and oval-shaped. The peel is light orange, smooth, rich in essential oils. The pulp is slightly tangy and divided into 4-5 segments.
The round kumquat, Fortunella japonica, originates from Japan. The tree of this variety closely resembles that of the oval kumquat. As the name suggests, the main difference lies in the shape of the fruits—small but round, similar to miniature oranges. The fruiting occurs later, from November to February. The fruits of this variety are also entirely edible. Another difference lies in the leaves, slightly smaller and lighter in color.
Hong Kong Kumquat
The kumquat variety Fortunella hindsii is native to China. It is also known as the Hong Kong kumquat because it thrives spontaneously on the hills of this city’s natural reserves. With ancient origins, it appears as a small bush not exceeding one meter in height. It is very thorny, with small and narrow dark green leaves. It blooms in summer with small, white, fragrant flowers. The flowers are singular on the branches and produce many long-lasting fruits on the plant. They are the smallest citrus fruits, even smaller than a chickpea. The small fruits are globular, with smooth, bright orange skin. The pulp is rather tangy and inconsistent, containing seeds much larger than the overall size of the fruit. This kumquat variety is highly ornamental and less edible when consumed fresh. The Chinese use it to make a valuable spicy condiment.
One common feature among the different kumquat varieties, distinguishing them from other citrus fruits, is their resistance to cold. These small trees enter a dormant phase in winter, ceasing to produce new buds and shoots. Other citrus species, such as lemon, clementine, citron, orange, are much more sensitive and must be protected from intense cold. For this reason, these are almost exclusively cultivated in Southern Italy. Kumquats, given their small size, are perfect for container cultivation, even on balconies. They prefer slightly shaded or semi-shaded places, sheltered from strong winds. Be cautious not to keep the plant indoors, especially near heating, as it could cause damage. At most, if severe frost is expected, cover it with non-woven fabric (like this). In short, it’s an ideal fruit tree for urban settings: easy, ornamental, and productive. Nevertheless, kumquats can also be cultivated in open soil, in which case their size will slightly increase over time.
Soil and Fertilization
Kumquats are usually sold in containers, already formed and full of fruits. After a brief period of adaptation to its new home, it needs to be transplanted into a larger container. Preferring slightly acidic soils, for transplantation, we recommend a mix of soil for acid-loving plants (find here) and normal garden soil (which you can which you can find here), amended with ground lupines (which you can find here), excellent for fertilizing potted citrus plants. With this mix, you’ll ensure healthy and vigorous growth for your kumquat plant. Transplanting into the larger container can be done once every two years, always using a balanced mix of soil and a bit of organic fertilizer. If the plant is cultivated in open soil, fertilization can be done once a year.
Regarding irrigation, the kumquat is not too demanding. However, it still needs attention, especially when cultivated in a pot. Check the soil moisture, if it’s too dry, water it without overdoing it. This operation, naturally, will be more frequent in the hot summer months. Be cautious of water stagnation that can cause root asphyxiation, leaf yellowing, and rot. To prevent this issue in cultivation, it’s sufficient to fill the bottom of the container with expanded clay (like this one).
Not being a plant with lush growth, the pruning interventions to be performed are limited. After harvesting, at the end of winter, it’s good to prune the plant a little, removing suckers and dry or broken branches. You can also remove some inner branches to aerate and provide more light to the canopy.
Biological Pest Defense
Compared to citrus fruits, kumquat is hardy and doesn’t particularly suffer from pest attacks. However, they can still occur. The most feared insects for this plant are the cottony cushion scale and aphids, both pests we’ve already discussed.
Another bothersome insect for kumquat is the citrus leafminer. This can be eradicated biologically using bacillus thuringiensis varietà kurstaki. It’s important that the bacillus is used during the larval stages of the insect. Adults are monitored using pheromone traps and chromotropic traps.
Uses of Kumquat
Besides being consumed fresh, the fruits of the Chinese mandarin are excellent for transformation. You can prepare tasty jams, candied fruit, and even a delicious kumquat liqueur, excellent as a digestive. This citrus fruit has excellent dietary properties. It is rich in vitamins C, A, and minerals like potassium, iron, phosphorus, and magnesium. It’s also rich in carotenoids that color the skin. Thanks to these substances, consuming this fruit boosts the immune system and prevents aging due to its antioxidant properties.