Now the main producers are China, Italian, Greek, Spanish and American.
Plant morphology and growth conditions
This kind of tree is more open, with many needles on its branchlets, and its tender tips are often purple. Petiole short, wings inconspicuous. White with purple, slightly fragrant, solitary or 3 ~ 6 flowers in racemes. Citrus fruits are yellow and shiny, oval or obovate, with papillae at the top, large and obviously sunken oil cells, sour peel and 8 ~ 12 pulp petals, which are difficult to separate. The seeds are ovoid, and most of them are single embryos. There are dozens of cultivated varieties, mainly Eureka and Lisbon.
Lemon is one of the least cold-tolerant citrus varieties. Suitable for places where it is warmer in winter, not too hot in summer and the temperature is relatively stable. Cutting propagation is very easy to survive, but grafting is often used in production, with rough lemon (a hybrid of lemon) with developed root system as the rootstock. Suitable for planting on warm gentle slopes with deep soil layer and good drainage. It blooms all year round and is open 3 ~ 4 times a year. Fruit is rich in vitamin C and citric acid. There are lemon oil with special fragrance and vitamin P in the oil cells of the peel, which are harvested after full growth and do not turn yellow, and then ripened with ethylene to make the peel turn yellow. It is resistant to storage and transportation. Besides fresh food, you can also make various drinks and extract lemon oil. There is little cultivation in China, and there is a kind of "Beijing lemon" in the north, which has no mastoid top, weak acidity and fragrance, and is only potted for viewing.
Planting method and growth cycle
Untrimmed lemon plants can be as high as 3 to 6 meters. The young leaves are obviously red and then gradually turn green. Some varieties have angular young branches; Some varieties have spikes between leaf axils. Flowers are large, fragrant, solitary or clustered; The bud is reddish, the petals are white and purple, which can be used to make drinks, contain vitamin P and extract lemon oil. The fruit is oval with a wide and short papilla at the top. 8 to 10 disc; It is yellow when it is ripe. Some varieties have thick exocarp, white mesocarp, spongy and almost tasteless, which are the main sources of commercial pectin. Seeds are small, ovoid and pointed; Occasionally seedless. The pulp tastes very sour. The main acid is citric acid, accounting for more than 5% of the total fruit juice. Lemon juice is rich in vitamin C and contains a small amount of vitamin B. After the Crusaders discovered lemons in Palestine, lemons began to spread all over Europe. At present, the cultivation of lemon trees in most tropical and subtropical regions is limited. Commercial lemon trees are usually propagated by budding, and the coastal areas of Italy and California are most suitable for growing lemons. Generally planted in orchards, the spacing between plants is 5 to 8 meters. Generally, flowers bloom all year round, and fruits are harvested 6 to 10 times a year. Mature commercial fruit is about 5 cm in diameter. Fruits are generally harvested before ripening and can be preserved for 3 months after treatment. Fruiting begins in the third year after planting and reaches commercial fruit in five years. The average annual output of each tree is 1500. Because lemons are easy to bruise, wear gloves when picking them.
Potted lemon
Potted lemons, if not properly managed, often only bloom, but bear no fruit or little fruit, or even do not bloom. In order to make potted lemons blossom and bear fruit every year, scientific management must be carried out in water, fertilizer and pruning, so as to achieve fruitful results. The main links of management are as follows:
Reasonable pruning-there are two reasons for pruning potted lemons. First, the pot is small, the soil is small, and the nutrients provided are limited, which can not meet the needs of lemon growth and must be pruned; Second, through pruning, the rational distribution of nutrients in the tree can be adjusted, so that limited nutrients can be supplied to buds and leaves to form more fruiting branches, thus achieving full flowering and fruiting branches. The new shoots of potted lemons must be pruned intensively before they germinate. First of all, we should remove dead branches, diseased branches, clustered branches, inward branches, cross branches and sprouting branches. Weakly cut strong branches, leaving 4 or 5 full buds; Strong pruning of weak branches leaves 2 or 3 buds, so that each branch can grow stronger spring shoots. After the spring shoots are fully grown, in order to control their imaginary length, they can be lightly cut and 3 or 4 branches can be cut off. When the new shoots grow to 6 ~ 8 knots, it is necessary to remove the heart to induce more summer shoots.
"Water-locking" before flowering-In order to prevent the summer shoots from growing too vigorously, at the same time, the trees should accumulate nutrients and promote the formation of buds, and "water-locking" the potted lemons before the arrival of summer. The specific method is to gradually reduce the water supply to potted lemons more than ten days before the summer heat; In the first 5 days, the water was stopped, the basin soil was exposed to the sun, a lot of water evaporated, and the basin soil was dry; Due to the lack of water in roots, branches and leaves lose water, and leaves wither and curl. In order to prevent the leaves from dehydration, water can be sprayed on the leaves in the morning and evening, and a small amount of water can be sprayed on the pot soil at the same time, so that the axillary buds of lemon will expand day by day under the condition of drought and not dying, and the color of the buds will turn from green to white. When most axillary buds turn from green to white, "withholding water" will succeed in promoting flowers. At this time, the water supply of potted lemons should be restored in time.
Protect the flowers and fruits-after the lemon blooms, in addition to applying thin fertilizer once a week, it is also necessary to dilute the flowers and fruits. Sparse some buds before flowering; After the flowers wither and set fruit, some young fruits in inappropriate positions should be thinned out to reduce the consumption of nutrients, so that the limited nutrients can be concentrated on the preserved flowers and fruits, and the fruits can grow bigger and better. In the process of fruit growth, if the fertilizer and water are sufficient and the plants are nutritious, some branches will sprout new buds, and the growth of new buds will inevitably divert some nutrients, which will affect the growth of fruits. In order to protect the fruit, the new buds should be smoothed in time. When the fruit turns yellow, stop fertilizing, reduce watering and keep the soil moist and slightly dry. If we continue to give too much fertilizer and water, the fruit will ripen and fall early, shortening the viewing time.
Rational fertilization-lemons like fertilizer, and usually apply more thin fertilizer. Apply decomposed liquid fertilizer once before the plants germinate, and then apply liquid fertilizer mainly containing nitrogen every 7 ~ 10 days to promote more branches and leaves and more spring shoots. Fertilize in time after each coring to promote the early maturity of branches. In the process of lemon growth, you can sprinkle some cake fertilizer on the basin surface, so that some fertilizer penetrates into the soil every time you water it, which can enhance fertility. After autumn, fertilization will be reduced, plant nutrition will be avoided, autumn shoots will be promoted, and fruits will compete for nutrients, leading to fruit drop.
Turn over the pot-potted lemons have limited nutrient supply due to lack of pot soil. After years of lack of soil fertility, lemons will weaken year by year, with fewer flowers and fewer fruits. In order to keep the lemon blossom and bear fruit every year, it is necessary to turn over the pot. The best turning time is half a month before lemon germination. Before turning over the pot, prepare a pot that is one size larger than the original pot, take the lemon out of the pot, and don't break the mud. Cut off the topsoil with a thickness of 1 and 2 cm along the mud mass, cut off the dead roots and rotten roots, cut off the soil with a thickness of 1cm at the bottom of the mud mass, and take out the tiles embedded in the bottom of the original pot. The drainage holes of the new pool are laid with tiles. First, lay a drainage layer with a thickness of 2 or 3 cm, and then lay a layer of nutrient-rich culture soil with a thickness of 4 or 5 cm, which is mixed with a small amount of calcium superphosphate. Then put the lemon mud balls into the pot, fill the culture soil around the mouth of the pot, slightly compact the pot soil, water the roots, put it in a ventilated and semi-cool place, and put it back in place for daily management after one week.