Introduction to Finger Citron Propagation and Seedling Methods: Quickly Master the Key Points of Raising Seedlings
Finger citron (Citrus medica var. sarcodactylis) is a shrub or small tree in the genus Citrus, family Rutaceae. It is a tropical and subtropical plant that prefers a warm, humid environment with plenty of sunlight. It is cultivated in various places south of the Yangtze River in China, and in the southern provinces and regions it is mostly grown in courtyards or orchards. It is usually used as a traditional Chinese medicine, or grown as an ornamental plant because of its unusual fruit shape, and it has extremely high cultivation value. Now let us take a look at how finger citron seedlings are propagated!
Air Layering
Air layering of finger citron is best carried out from May to July. Choose a vigorously growing overly tall branch or a branch that has already set fruit firmly. Make an upward slanting cut from below on the branch, deep enough to reach the pith. Place the cut branch into a felt tube, tie the lower part tightly, fill the tube with soil and pack it firm, tie the upper part tightly, and set up a support. Water it every day. When the temperature is high and there is plenty of moisture, roots will form in 20 to 30 days. If there is a finger citron fruit on the layered branch, you must wait until the fruit ripens and turns yellow, about 90 days, before separating it from the mother plant.
Grafting Propagation
1. Approach grafting: carry out in early August to September. For the rootstock, choose a vigorous 4- to 5-year-old plant with a stem diameter of 2 to 3 cm. Cut away the branches below the branching point at the base of the stem, leaving only one branch. Then on one side of the spot where the branch was removed, shave off some of the bark downward. Next, choose a branch that grew in the previous spring or autumn as the scion, similar in thickness to the rootstock and 5 to 7 cm long. On the lower side of the scion, also shave off part of the bark below. Then press the cut surface of the rootstock against the cut surface of the scion so that the two surfaces fit tightly together, and bind the middle tightly with plastic film. After about one week they will have healed together.
2. Side cleft grafting: in early to mid-March, cut the rootstock flat at 5 to 7 cm above the ground, smooth it with a grafting knife, and choose a smooth part with a little wood to make a slanting cut 1 to 1.5 cm deep. The scion should retain 2 to 3 buds, and its lower end should be cut into a wedge shape 1 to 1.5 cm long. Then align one side of the rootstock cut with the cut bark of the scion and insert it tightly into the rootstock cut, binding it with plastic film. Generally after half a month it will have healed and sprouted. At this point, loosen the soil and remove weeds. After 45 to 60 days, it begins to send out shoots; at this time the binding material must be removed, otherwise the new shoots are liable to bend.
Cutting Propagation
1. Cuttings: before cutting, choose a vigorous 7- to 8-year-old mother tree, cut off vigorous, pest- and disease-free old healthy branches, remove the leaves and tender tips, and cut them into cuttings 17 to 20 cm long. The survival rate of cuttings is over 90%, and the seedlings grow very vigorously. Branches from young trees or water sprouts must not be used, because such branches often bear little fruit after planting.
2. Land preparation: for the finger citron cutting bed, it is best to choose sandy soil with a relatively deep soil layer, so that the seedlings can be lifted later. After the cutting site is chosen, plow deeply and harrow finely, and at the same time apply human and livestock manure water. Then make raised beds 1.3 m wide, usually with furrow width of about 30 cm and depth of about 20 cm.
3. Cutting: cuttings can be taken in spring from February to March and in autumn from August to September, with autumn cutting being the best. When inserting, open horizontal furrows on the bed with a furrow spacing of 23 to 27 cm, and insert the cuttings into the furrows at a plant spacing of 15 to 17 cm. Never insert them upside down. Usually about 12,000 to 15,000 cuttings are needed per mu. After inserting, cover with soil and press firm so that one bud at the tip is exposed above the soil surface; water if the soil is dry.
4. Management: after cutting, finger citron must be watered and irrigated at any time, and a shade frame must be built. When there is a lot of rain, drainage work must be done well. When the seedlings are 7 to 10 cm tall, remove the clustered weak seedlings, leaving only one strong seedling per plant. Weed in time, and apply light human and livestock manure water or ammonium sulfate 3 to 4 times. After one year of cultivation they can be transplanted.
A Brief Discussion of Chayote Propagation and Seedling Raising
Chayote, also known as fist melon, vegetable pear, and chayote squash, is a perennial climbing herbaceous plant in the genus Sechium, family Cucurbitaceae. At present, in northern China it is mostly grown as an annual. There are mainly two varieties, white-skinned and green-skinned. Chayote is deeply welcomed by people for being storage-tolerant, transport-tolerant, having few pests and diseases, and having a unique flavor. Chayote originated in Mexico and the West Indies. After it was introduced into China, for a long period it was mainly grown in the south. In recent years, with the adjustment of planting structure and the continuous improvement of cultivation facilities, chayote cultivation has developed rapidly in the north, and some have begun to move toward large-scale and intensive trends. It has now become an important way for farmers to develop the economy and increase income.
The structure of chayote differs from that of general cucurbit plants: each fruit has only one seed. When the seed matures, it almost fills the entire cavity, so that the seed is tightly connected to the fruit and difficult to separate. If the seed leaves the fruit, it is not easy for it to germinate and survive, and it is even less possible to dry and store the seed as with general cucurbit plants. Based on recent propagation and seedling-raising techniques, the author has compiled the following, for reference only.
I. Whole-fruit propagation
This is the method of using the whole fruit as sowing material for propagation. This propagation method is the most basic and is currently the most widely used. Propagation by this method makes it relatively easy to raise vigorous seedlings, but because the seed fruit is rather large, there are many inconveniences in storage, transport and transfer, especially when a large number of seedlings is used, there is also the problem of relatively high cost, as well as losses caused by rotting in a series of environments such as storage, sprouting and seedling raising due to poor control of temperature and humidity.
Seedling raising by this method mainly has 3 basic steps: first, select good seed fruits; the seed fruit is required to be undamaged, free of freezing injury, well matured, and a medium-sized fruit weighing about 200-300 g; second, sprout the seeds well. When sprouting, usually put the selected seed fruit into a plastic bag or bury it in wet sand. The relative water-holding capacity of the sand should be kept at about 75%; generally, when grasped by hand it does not stick to the hand, and when squeezed hard no water seeps out. The temperature should be controlled at 15-20 degrees, but note that during sprouting the temperature should not be increased blindly, so as to avoid thin and weak sprouts. After about 15 days, the top end of the fruit cracks open and sparse roots grow out one after another; third, strengthen seedling management.
For raising a small number of seedlings, generally a flower pot with a diameter of 20-30 cm or a plastic bag with holes punched in the bottom can be used; for raising a large number of seedlings, a seedbed is generally used. The specific method is to place the sprouted seed fruit with the sprouting end facing up and the stalk end facing down, and plant it upright or slanting in the seedling pot or seedbed. In northern regions, in winter, sunlight greenhouses, plastic tunnels and similar facilities can keep the temperature relatively well controlled at about 10-30 degrees, making them extremely ideal places for raising seedlings. After planting, pay attention to heat preservation and moisture retention. Before emergence, control the temperature at about 20 degrees; after emergence, lower it to 12-15 degrees, so as to help raise strong seedlings. If the seedlings grow leggy, pinch out the growing tip when there are 4-5 leaves, keeping 1-2 strong side branches.
II. Naked-seed propagation
Also called bare embryo propagation, that is, the method of using exposed seeds without seed coat for propagation. With this method, seedlings emerge quickly and the emergence rate is high, transport is convenient, and the fruit after the naked seed is removed can still be used economically; it is relatively suitable for intensive seedling raising. However, this method has relatively strict technical requirements. At present, because general technical materials introduce this method relatively little and because of insufficient promotion and other reasons, it is rarely used in actual production. To raise seedlings by this method, first place the selected seed fruit in an environment of about 20 degrees to sprout. When the embryo base has developed well and the young sprout has grown to about 3 cm, gently split the suture line at the tip, use sterile tweezers to move the embryo, then take it out and plant it in a seedling pot or seedbed. Seedling-stage management is the same as above.
III. Cutting propagation
This propagation method is carried out on the basis of whole-fruit seedling raising. At present, there are mainly 2 cutting methods used: one is to make use of the clustering habit of the chayote plant, that is, one chayote can grow many clustered sprouts. When the clustered sprouts grow to about 10 cm, use a small knife to cut off the sprout seedlings together with the mother tissue and fibrous roots. To improve the survival rate of the sprout seedlings, they can be treated with a rooting agent and then planted and cultivated as individual plants. The other is to raise chayote seedlings in advance, cultivate strong seedlings with many side vines, then cut the seedlings into sections, each section with 2-3 nodes, treat them with indoleacetic acid or a rooting agent, and insert them into the seedbed for seedling raising. The above cutting propagation and seedling raising is economical and feasible, but management is very strict, and the seedlings produced often grow weakly and the mature plants have low yield, so it is also rarely used in current production. When raising seedlings by this method, attention should be paid in the early growth stage to strengthening fertilizer and water management, to promote early sprouting and fast sprouting.
Propagation Methods of Golden Finger Citron
Jinhua finger citron seedling raising is carried out by asexual propagation. The main methods include cuttings, grafting, high-branch layering, and tissue culture. Because finger citron is parthenocarpic and the fruit contains no seeds, under natural conditions it cannot be propagated sexually to raise seedlings.Finger citron propagation methods are divided into two methods: cutting and grafting:
(I) Cutting method
Jinhua finger citron branches root easily, and cuttings can be taken in three seasons of the year. This method has the advantages of a high survival rate, fast growth, bearing fruit 20 months after cutting under technical guidance, relatively simple method, and low cost of cuttings. However, its lifespan is relatively short; generally after about 15 years the plant begins to decline and dies of old age.
1. Seedbed establishment
If you want good finger citron, healthy seedlings are the most important. Only with strong seedlings can good trees grow, and only with flourishing trees can good fruit be produced. "A good seedling is half the harvest" is a basic experience we have gained from long practice. To raise good Jinhua finger citron seedlings, work must be done well in such aspects as the seedbed, seed selection, cutting, and management.
The seedbed is the hotbed for propagating Jinhua finger citron seedlings. You must choose a plot that is sheltered from the wind and facing the sun, with sufficient light, abundant water sources, good drainage and irrigation, loose soil, free of toxins and contamination, favorable for transplanting, and convenient for management. The area of the seedbed should be determined by the amount of finger citron branches: make more if there are many, less if there are few, so as to save land and labor. After the seedbed site and area are determined, begin deep plowing and leveling the land. You must break up the soil clods as carefully and meticulously as a girl embroidering, the finer the better, and remove weeds, then make a seedbed 100-120 cm wide and about 20 cm high, with unlimited length. Then spread a 2 cm thick layer of red sand or yellow sand on the surface of the seedbed (as shown in Figure 2). Red sand or yellow sand generally contains few weed seeds and serves to prevent weeds from growing. A cutting density with spacing of 5-10 cm is appropriate.
In order to make the seedbed free of toxins, contamination and weeds, black plastic film can be used instead of red sand or yellow sand to cover the seedbed, then insert the cuttings and spray water. If black plastic film is used to cover the seedbed in hot summer, a 65% shade net should be used over the seedbed to provide shade, to prevent the black film from absorbing a large amount of heat and scalding the cuttings. Black film has the effect of preserving heat and moisture, promotes rooting of cuttings, and makes the root system well developed and vigorous, and weeding work can be dispensed with.
2. Selection of cuttings
As the saying goes: "Dragons beget dragons, phoenixes beget phoenixes, and mice are born to dig holes." This shows that choosing good varieties for cultivation is extremely important. When selecting cuttings, be sure to achieve four do's and four don'ts: use old branches, not tender branches or new branches; use strong branches, not weak or damaged branches; use healthy branches, not diseased branches; use the green-skinned variety, not the white-skinned or yellow-skinned varieties. Tender branches, weak branches, damaged branches, diseased branches, and the white-skinned and yellow-skinned varieties are poor branches. Not only do they have a long growth period, but they also do not easily set fruit. The so-called old branches refer to mature branches on the Jinhua finger citron tree that can set fruit; cuttings from thick, robust one-year-old aged branches are best. Such branches can bloom and bear fruit after two years of cultivation. Collect cuttings according to the above requirements, each branch about 7-10 cm long, that is, 3-5 leaves as one segment (too long is wasteful, too short is not easy to survive). When cutting, make a clean single cut without leaving anything extra. Some branches retain two or three leaves; others retain none at all. According to practical experience: "Cuttings that retain two or three leaves root first and then sprout; cuttings that retain no leaves sprout first and then root."
3. Cutting time and operation
Finger citron cuttings are mainly taken in spring and summer, carried out in conjunction with pruning work. Spring is in March to April each year, during the spring pruning after finger citron is brought out of the shed; summer is from late July to early August (generally completed before the Beginning of Autumn) during summer pruning. Use the pruned branches, select thick, robust branches free of pests and diseases as cuttings, remove leaves and thorns, and cut them into cuttings 8-10 cm long, with the cuttings bearing more than 3 buds. Generally after 15 to 20 days, the young seedlings have rooted, changing from white roots to yellow roots, with a high survival rate. If the collected branches can maintain a certain humidity, they can be stored for about 10 days and still survive at 95%. When collecting branches, the scissors must be sharp, cutting with a single cut so that the cut surface remains flat; a damaged cut surface gives a low survival rate.
4. Seedling management
According to the growth habits of Jinhua finger citron, focus on doing good work in such aspects as temperature and humidity, pests and diseases, and clearing weeds.
(1) Light. Sunlight is the energy source for photosynthesis in seedling leaves. However, when sunlight is intense and the temperature is above 40°C, young seedlings are easily sunburned, so a simple shade frame must be built (Figure 4), open on all four sides, with pine branches or a shade net on top, to prevent scorching by the hot sun. When the temperature is below 0°C, young tender seedlings are easily frozen, so overwintering frost protection facilities must be made: use bamboo strips and nylon film with rice straw laid inside to make an overwintering shed.
(2) Watering. Use a watering can to spray water evenly; do not splash water. Keep the soil at a certain humidity, but it must not be too wet; it is enough that the soil does not dry out and turn white. On cloudy and rainy days, guard against waterlogging and dig ditches for drainage. Too much or too little water can both affect the growth of young seedlings, and in serious cases can lead to failure in seedling raising.
(3) Weeding and fertilizing. Weeds both consume nutrients and harm the growth of young seedlings, so they must be pulled out frequently; never let them grow and cluster, so that the seedbed is clean and fresh, with only seedlings visible and no weeds. When weeding, pull carefully by hand, and never damage the root system of the young seedlings. If black film is spread on the seedbed at the time of cutting, and the cuttings are inserted directly through the black film into the soil, the black film can prevent weeds from growing, and weeding work can again be dispensed with. The finger citron root system is distributed in the
shallow surface layer, and the roots can secrete organic acids that dissolve minerals in the soil, which helps root absorption. During seedling raising, there is no need to apply much fertilizer. When the new shoots of the young seedlings mature, a small amount of farmyard manure or compound fertilizer can be used, fertilizing according to the condition of the seedlings; heavy fertilizer must not be used.
(4) Pests and diseases. If pests and diseases are found and allowed to spread, the damage is by no means small. For relevant control methods, please refer to the "Pest and Disease Control" section.