How to cultivate osmanthus? Osmanthus propagation methods and disease control

Osmanthus is one of China's ten traditional famous flowers, a precious aromatic and ornamental plant, evergreen year-round, with graceful branches and a rich fragrance. So how should osmanthus be cultivated and managed? Follow along with the editor to find out.

Cultivation conditions: Osmanthus is a temperate plant that prefers a warm, humid environment and is not tolerant of severe cold. It is suited to subtropical climate regions, with an optimum growth temperature of 15-28°C. Osmanthus is a long-day plant that prefers strong sunlight and can withstand high temperatures, so it is best planted in a sunny, well-ventilated spot. Osmanthus likes moisture and fears waterlogging, but it also has some drought tolerance, so during cultivation take care to prevent waterlogging and drain excess water in the rainy season. Osmanthus is not very demanding about soil and develops well in sandy acidic soil; it dislikes alkaline soil and fears coal smoke. Generally, early spring is chosen for planting.

Propagation methods: It can be propagated by sowing, layering, grafting and cuttings.

Sowing

Osmanthus fruit ripens in April-May. When the fruit turns purplish-blue, harvest it, remove the peel, place it in a cool spot to let the seeds dry naturally, and store them in sand. Sow in October of the same year in autumn, or in spring of the following year. Sowing propagation generally uses the drill method; after sowing, cover with straw to retain moisture and set up a shade shed.

Layering

Air layering is mostly used. In spring, select a branch of suitable thickness, choose an easily bendable section, cut or ring-bark it with a sharp knife down to the xylem, wrap humus soil around the cut with plastic sheeting and tie it firmly, keeping the soil moist. By autumn, once roots have formed, cut it away from the mother plant and plant it.

Grafting

Approach grafting is mostly used, though cleft grafting can also be done. The rootstock is often a seedling osmanthus, or privet (Ligustrum), small-leaf privet (Ligustrum sinense), fringe tree (Chionanthus retusus), etc.; the survival rate is relatively high and grafted seedlings grow fast. Cleft grafting is done in spring before the plant sprouts new buds; approach grafting is mostly done from summer to before the onset of the dog days, and when approach grafting, choose scion and rootstock branches of similar thickness. In the south, cleft grafting is more common; in the north, approach grafting is more common.

Cuttings

Before the plant sprouts in spring, select well-developed, robust 1-year-old branches, cut them into 5 to 10 cm cuttings, remove the lower leaves, keep 2 to 3 green leaves at the top, insert them into sandy soil or peat, cover with plastic film, place in a shaded spot, and keep the temperature at 20 to 25°C. After the beginning of autumn they will root and can be transplanted. Alternatively, in summer after the new shoots stop growing, take cuttings from current-year branches using the same method.

Disease control

Brown spot disease mainly harms the leaves. After infection, round or nearly round brown spots appear on the leaves, 2 to 10 mm in diameter. Brown spot disease generally occurs from April to October; old leaves are more susceptible than young leaves, and in severe cases it causes extensive scorching of the leaves. Control methods: 1. When the disease is about to appear, spray once every 7 to 10 days with 65% zineb wettable powder at 400 to 600 times dilution, or 50% benomyl wettable powder at 1000 to 1500 times dilution, for 2 to 3 consecutive applications; 2. Strengthen water and fertilizer management, apply more potassium fertilizer, pay attention to ventilation and light penetration, and improve the plant's disease resistance; 3. In the early stage of the disease, spray 50% carbendazim at 500 to 800 times dilution or 75% chlorothalonil at 600 to 800 times dilution; 4. Promptly clean up diseased branches.

Dieback spot disease: It generally occurs from July to November. In the early stage it invades from the leaf margins and leaf tips, producing light brown spots on the leaves, which then gradually expand into nearly round or irregular large brown patches with dark brown edges. Control methods: 1. In winter, thoroughly remove diseased leaves and burn them in a centralized manner or bury them deep to reduce overwintering pathogens; 2. Spray once with 70% mancozeb wettable powder at 500 times dilution and Yeku at 800 times dilution.

Black-winged whitefly: Adults and larvae gather on the undersides of leaves to suck sap, forming yellow spots at the feeding sites, causing leaves to turn yellow, wilt, and even die. In severe cases they secrete large amounts of honeydew, which easily induces sooty mold and blackens the branches and leaves. Control methods: Upon discovering the pests, immediately spray 2.5% deltamethrin or abamectin (7051) insecticide at 2000 times dilution, Imidacloprid (Aimeile) at 30000 times dilution, or Actara at 10000 times dilution, etc.

Propagation methods and pest and disease control of potted silver-edged variegated osmanthus

How is silver-edged variegated osmanthus planted? The following article from Huinong Net introduces the key points one by one, covering propagation methods, grafting techniques, daily management, and pest and disease control of potted silver-edged variegated osmanthus.

1 Propagation

Silver-edged variegated osmanthus can be propagated by cuttings, grafting, layering and other methods. However, in production, layering has a relatively low survival rate, while cuttings and grafting have high survival rates and are easy to perform, making them suitable for large-scale cultivation and widely used in actual production.

1.1 Cutting propagation

Cutting propagation is divided into soil-based cutting propagation and soilless cutting propagation. The two use different cutting media, but the techniques and operation methods are basically the same.

① Cutting time. It is mostly done in June to July each year. A soil temperature of 20°C to 25°C favors rooting and promotes survival. In some places it can also be done in autumn. The specific time can be determined according to local production practices.

② Cutting medium. Silver-edged variegated osmanthus prefers slightly acidic soil and grows poorly in alkaline or neutral soil. For cuttings, choose red loam rich in trace elements or sandy soil rich in humus; you can also use yellow soil that is free of impurities, of superior clay quality, and with good permeability. Soilless propagation mainly uses peat and perlite as the medium. Before cutting, mix and stir the two evenly in a 1:1 ratio.

③ Collection of shoots and treatment of cuttings. Two to three days before taking branches, the mother plant should be disinfected and sterilized. Choose current-year semi-lignified branches that are robust, well developed, free of pests and diseases, free of dead branches and yellow leaves, and with sufficient nutrition as cuttings. Branches that are too tender rot easily, while those that are too old are difficult to root. It is best to collect branches on cloudy days or early dewy mornings; the cut cuttings should be placed in a clean plastic basin or bag and kept out of strong light. Cuttings should be inserted immediately after cutting, generally with two leaves. After the cuttings are prepared, soak them in 100 mg/L naphthaleneacetic acid solution for 3 seconds, let them dry, and then insert them.

1.2 Seedbed cutting propagation

① Preparation of the cutting bed. Choose flat ground for the cutting bed, with soil mostly sandy loam or acidic red loam. First deep-plow the land and remove weeds. Enclose a 1 m wide seedbed on the ground with iron plates or wooden boards; the length is up to you. Dig drainage ditches between the seedbeds. The drainage ditches should be divided into wide and narrow ditches; wide ditches for drainage and narrow ditches for field work in production. Pour red loam into the seedbed and level it with a hoe; the seedbed height is 8 to 10 cm. Disinfect the soil with potassium permanganate 1 week before cutting. Water the seedbed before cutting, and insert the cuttings after the water has seeped in.

② Cutting method. Place the prepared cuttings on both sides of the seedbed, with at least two people working on each side respectively. When inserting, keep them neat, with a depth that just covers the leaf stalks, and a density such that the leaves slightly overlap. After cutting, water thoroughly to settle the roots; 1000 plants can be inserted per square meter.

1.3 Soilless cutting propagation

Soilless cutting propagation is mostly done from May to June. First put the soilless medium into 72-cell plug trays, then spray with water to moisten; after the water has seeped in, insert the cuttings. The cutting method is the same as soil-based cutting. After cutting, to prevent water from accumulating at the bottom when the cuttings root, place an empty plug tray under each plug tray containing cuttings.

1.3.1 Management after cutting

① Temperature and humidity control. Osmanthus has strict requirements for temperature and humidity, so water should be applied timely during the seedling stage, and the ground must not be too wet or too dry. Within two months after cutting, water once every 2 to 3 days, but the ground must not be waterlogged, and during the dog days the ground must not be dry. The temperature should preferably be 22°C to 25°C, and the humidity above 90%, to promote callus formation and rooting.

② Reasonable lighting. After cutting, as summer arrives, to prevent the leaves from being scorched by sunlight, set up black shade netting over the seedbed for shading.

③ Winter insulation. For autumn cuttings, after winter arrives, build a plastic greenhouse to retain heat and moisture, ensuring the seedlings survive the winter safely.

④ Disease control. Seedling-stage care cannot be neglected. If disease is found, spray promptly for control to ensure survival. The main disease of silver-edged variegated osmanthus is anthracnose; after infection, gray lesions form in the middle of the leaves. If not controlled in time, it will spread to other plants. Spray carbendazim at 1000 times dilution for control, once a week, for 3 to 4 consecutive sprays.

With careful management, the inserted osmanthus cuttings will root and survive after 4 months. If inserted in autumn, they can be transplanted in spring of the following year.

2 Grafting

2.1 Grafting time

Grafting is mostly done from March to April; softwood grafting can also be done from May to June.

2.2 Preparation before grafting

Pruning saw, scissors, grafting knife, tying string and transparent plastic bags; the grafting knife is best a commonly used double-edged blade.

2.3 Rootstock selection

Choose the base of a 3-year-old plant with strong moisture tolerance and rot resistance and a well-developed root system as the rootstock. At present, wild osmanthus and fast-growing cultivars such as 'Susheng Jingui' are mainly used. Because wild osmanthus has strong moisture tolerance, strong wear resistance, a well-developed root system and thick branches, and fast-growing osmanthus heals wounds quickly and has a high survival rate, they are relatively ideal rootstocks. Scion selection: choose new branches from mother plants with high ornamental value, good growth and no pests or diseases as scions. When grafting, choose a place without light and with little wind, to favor healing of the graft union.

2.4 Old branch grafting

First saw off the top of the selected rootstock. To ensure the plant looks good in the future, the rootstock can be left 20 to 30 cm, and use a small blade to smooth the cut of the rootstock so it is not uneven. Also use a blade to cut the bottom of the scion at a 30° angle. Make two cuts first, then finally cut it into a triangular shape. When grafting, ensure each scion has a bud, and use a blade to make a slanted cut at the top of the rootstock. Do not damage the xylem layer, and the cut should be slightly longer than the length of the wedge face of the scion. Then insert the scion at an angle, ensuring the scion and the rootstock cut fit tightly together. One rootstock can be grafted with two scions. Then tie it firmly with plastic string. Since the climate has not fully warmed up in March to April, to prevent the plant from freezing to death, also put a plastic bag over it and tie it tightly with string. Finally, promptly place the newly grafted plant in a greenhouse to ensure the grafted seedling survives.

2.5 Softwood grafting

Also called bud grafting, it has a high survival rate, reaching over 95%. First cut off the sprouted branches, leaving 2 to 4 cm. The branches must not be lignified, otherwise survival will be affected. Generally the number of branches on the rootstock varies; at least 2 are needed for grafting. When cutting the buds, use a blade to make a slanted cut on the lower part of the branch, on both the front and back sides, shaping the graft site into a flat form. Then use a small knife to split the branch from the middle; the cut must not be too deep, depending on the length of the scion. Then insert the scion directly into the branch; after each is inserted, tie it firmly with plastic string. After grafting is complete, cover with a plastic bag and place it in a plastic greenhouse.

2.6 Management after grafting

Grafted seedlings survive relatively quickly, but you must still manage the temperature and humidity in the greenhouse. If the climate is too humid, promptly open the greenhouse for ventilation; to prevent the ambient temperature from changing too quickly, cover with shade netting. After 1 year of careful management following grafting, a new plant will have grown.

3 Potting and planting out

Pot selection and nutrient soil preparation. For pots, choose plastic containers or gallon containers. When cultivating, pay attention to coordinating the ratio of pot diameter to plant crown diameter. Generally speaking, the crown spread of a large variegated osmanthus can be 1 to 2 times greater than the pot opening diameter. Use 8 to 10 cm plastic pots for 1-year-old seedlings, 10 to 14 cm containers for 2-year-old seedlings, and 30 cm containers for plants over 3 years old. Never use a large pot for a small plant, otherwise the wet pot soil will easily cause root rot. Osmanthus prefers loose, fertile, slightly acidic media rich in organic matter. For alkaline soil, mix in more humic acid or use 0.2% ferrous sulfate for soil improvement. For acidic soil, wood ash or lime can be used to neutralize it. Generally, the pot soil can be prepared by mixing leaf mold (or peat):garden soil:sand (or river sand) = 5:3:2, or half humus soil and half sandy loam as the growing medium. After the pot soil is prepared, the pH value should preferably be controlled at 5.5 to 6.5. You can also choose 30% decomposed sawdust + 40% coconut coir + 15% coarse river sand + 15% perlite, or peat:vermiculite = 1:1 for soilless cultivation.

3.1 Potting

Root systems are more developed after planting rooted cuttings or container-grafted seedlings, which also favors seedling survival, so variegated osmanthus can be potted and planted year-round. However, spring and autumn are the most suitable periods for potting, and transplanted seedlings must not have their roots damaged. When potting, first place a piece of plastic window screen over the hole at the bottom of the pot to prevent earthworms and other pests from entering the pot. When potting, place the seedling in the center of the pot at a suitable depth, then add the medium and press lightly around the edge of the pot with your hand; never press the root area, and leave a 2 to 3 cm gap between the medium and the pot rim for watering. After potting, since watering or potting can cause serious lodging of the seedling, promptly straighten it. If potting is done during the growing season, properly prune the upper branches and leaves to reduce water evaporation. At the same time, take measures such as shading and cooling and spraying water to retain moisture, until the plant sprouts and grows, after which normal management can be resumed.

4 Cultivation management

4.1 Growing environment and placement

Potted variegated osmanthus should be placed in a ventilated, sunny greenhouse with good drainage. The placement should facilitate both management and viewing. Generally, the nursery is divided into zones according to the size of the production seedlings, or according to the different water requirements and pH needs of different plants, with plants requiring the same environmental conditions placed in the same zone and given the same management measures, to facilitate management and plant growth and development. The placement density of plants should be adjusted in a timely manner as the plants grow, moving the pot spacing so that branches do not cross each other. Never place them too densely, otherwise pests and diseases are easily caused.

4.2 Watering

The pot soil should preferably be dry-wet alternating; it must not be too wet or waterlogged, otherwise root rot and leaf drop easily occur. Generally, water less before new shoots sprout or on rainy days. Usually, watering should keep the pot soil moisture content at about 50%. In summer under high temperature and dryness, watering should be sufficient: water once in the early morning and once in the evening each day, and use shade netting at noon to reduce the impact of high temperature. At the same time, frequently spray water on the leaves and around the flower pot to cool down, creating a humid local micro-environment.

Watering is best done with micro-sprinklers, with the nozzle directed at the container; this can also serve for fertilizing, and the fertilizer is applied evenly with good results. Soft water is preferable; if using groundwater or tap water, it needs to stand in a reservoir for a period of time. The best time to water is in the morning, which can reduce the occurrence of pests and diseases. In stormy weather, take care to drain accumulated water.

4.3 Fertilizing

Newly planted seedlings grow new roots in about 30 days, but because the medium for container potting is limited, they cannot obtain enough nutrients from the soil. To enable multiple shoot flushes in a year, regular topdressing is needed before each flush. The topdressing fertilizer must not be excessive, and un-decomposed raw fertilizer must not be applied, otherwise it easily burns the seedlings. Compound fertilizer is preferable for topdressing, but be sure to choose sulfur-based compound fertilizer and not fertilizer containing chlorine, to avoid salinization of the pot soil affecting normal plant growth. For fertilizing, nutrient solution or compound fertilizer can be used as topdressing; it is best to use a slow-release fertilizer with a nitrogen:phosphorus:potassium ratio of 21:5:12. Water-soluble fertilizer or compound fertilizer can also be dissolved in water and poured on, at a concentration of 0.1% to 0.5%, with topdressing once every 7 to 10 days during the growing season; fertilizing can be paused during the flowering period and the cold winter period. In addition, every half month spray once with a foliar fertilizer of 0.2% monopotassium phosphate and 0.2% silicon-boron-manganese fertilizer, to increase the thickness of new shoot growth, improve leaf function, and make the branches and leaves of the osmanthus plant look more attractive. Water-soluble fertilizers have high cost and good effect and can be used at the seedling stage. Compound fertilizers have low cost and can be applied to small seedlings and small-specification container seedlings. Silver-edged variegated osmanthus should not be given urea alone or nitrogen fertilizer alone, otherwise the silver-edged leaf color will turn green.

4.4 Light and temperature

Silver-edged variegated osmanthus is a light-loving tree species, but newly planted seedlings need shading to favor normal growth. In the harsh environment of high temperature, muggy heat and long drought, to help potted variegated osmanthus pass the summer safely, special attention should be paid to daily care and management. Potted plants must be cooled and protected from heat; for shading and cooling, it is best to use 50% shade netting in a high shed for shade, ensuring ventilation and air permeability.

Silver-edged variegated osmanthus has strong cold resistance, but in northern regions it cannot tolerate low temperatures below -10°C. At the cultivation site, when the temperature drops to severe cold in November, promptly build a plastic film greenhouse and take cold and freeze protection measures to protect the potted variegated osmanthus through the winter and prepare for the coming year's growth.

4.5 Regularly adjust pot spacing and loosen pot soil

When seedlings are first potted, place them pot against pot as much as possible. After a period of growth, promptly adjust the plant spacing appropriately. If the pot soil becomes compacted after watering, promptly loosen the pot soil so air circulates and the plants grow well. At the same time, remove moss and weeds from the soil surface.

4.6 Shaping and pruning

Potted variegated osmanthus is generally pruned into a single-trunk form. Starting from the seedling stage, keep 1 main trunk and pinch the top at the predetermined height of the trunk to make it sprout 3 to 5 side branches and form a crown. After that, prune once a year before sprouting in winter and spring, cutting out diseased and dead branches, overly dense branches and thin weak branches, and properly shorten plants that are strong on top and weak below or have a poor tree shape, to encourage adventitious buds to sprout from the lower part and grow new branches. However, pruning must not be excessive, otherwise vigorous water sprouts easily emerge and the number of flowers is affected.

For plants that grow tall but lack branches and leaves in the lower part, cut off the upper 2/3 or 3/4 or more of the main trunk to encourage new branches to grow from the lower trunk. The following year, all water sprouts or improperly positioned branches and other messy branches should be cut off, so that a full natural shape is formed. For trees that are top-heavy and grow too tall, shorten the upper strong branches by about 1/4 every year. At the same time, also cut out overly dense branches, thin weak branches, pest- and disease-damaged branches, water sprouts, and old branches that cannot bloom, to favor ventilation and light penetration. For all plants after shaping and pruning, water and fertilizer management should be strengthened. After shaping, if clustered suckers appear at the base or middle of the trunk, promptly remove them.

4.7 Repotting

Repotting is one of the important measures for growing variegated osmanthus well. Generally, repotting once a year is sufficient. When potting, mix in an appropriate amount of well-fermented pig manure or cake fertilizer as base fertilizer. Repotting can be done in the humid season. When repotting, cut away part of the soil (roots), retain part of the original soil (roots), add new soil, water thoroughly, and place in a shaded spot for management. After 15 days, it can receive light, but newly potted plants should be watered sparingly at first, just keeping the pot soil moist; once the root system has fully grown and stabilized, fertilizer and water can gradually be increased.

5 Pest and disease control

5.1 Diseases

Common diseases include leaf blight, anthracnose, brown spot disease, etc. If the bottom of the flower pot does not leak water, water accumulates in the pot, and over time the roots are damaged; when the ground temperature is high and evaporation is great, leaf blight easily appears. This disease often occurs from July to September and is mostly seen on the top leaves. Control methods: Spray 50% thiophanate-methyl and sulfur suspension concentrate at 800 times dilution for disinfection. In severe cases, spray 70% mancozeb wettable powder at 500 times dilution, or 30% copper chloride suspension concentrate at 600 times dilution, once every 10 days, for 2 to 3 consecutive sprays. Anthracnose mostly occurs on old leaves, with lesions mostly at the leaf tips and leaf margins, and it easily occurs under conditions of high temperature and high humidity and poor ventilation. Control methods: Careful maintenance; promptly cut off diseased leaves when found; water from the edge of the pot; after the disease occurs, immediately spray 25% anthracnose-ling wettable powder at 500 times dilution for 2 to 3 consecutive sprays, and it can be effectively controlled. Brown spot disease occurs at the leaf tips and leaf margins. Control methods are the same as above.

5.2 Insect pests

The main pests include leaf-rolling larvae, red spider mites, scale insects, white grubs, etc. Leaf-rolling larvae nibble on new tender leaves, causing poor growth or no growth of new shoots. Once they occur, spray 2.5% decis at 1500 to 2000 times dilution to kill them. Red spider mites mostly occur from May to August; the damaged areas lose chlorophyll, then show gray-white patches, and the leaves lose their luster. In severe cases a large number of leaves drop and the plant cannot bloom. You can choose Saomantjing or Kemandte at 2000 times dilution to spray the undersides of the leaves, which can effectively eliminate the damage caused by red spider mites. White grubs feed on osmanthus roots, causing dull leaf color and weak growth of potted flowers, and even the death of the whole plant; you can choose 40% chlorpyrifos emulsifiable concentrate at 1000 times dilution and pour it on the roots. If ventilation is poor and temperature and humidity are too high, the plant is easily harmed by scale insects, and in severe cases this also causes a large number of leaves to drop and branches to die. Prevention methods: Maintain ventilation and light penetration, and do not let the temperature get too high. In severe cases, spray Supujie at 1000 times dilution to kill them.

The above is all the content on the propagation and pest and disease control cultivation techniques of potted silver-edged variegated osmanthus. Because the article is rather long, it is recommended that you save it for study. If you have other needs, welcome to leave a message below the comments on Huinong Net!

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