How to Grow China Asters? Planting Methods, Precautions, and Pest and Disease Control Tips
China asters are often used in gardening and are an economical flower species. China asters come in a rich variety of colors, including blue, red, white, and yellow. So, what planting methods and precautions are there for China asters? What pests and diseases affect China asters, and how are they controlled? Let's find out together.
1. Planting Methods for China Asters
1. Watering
China asters prefer a moist environment but are afraid of becoming too wet. They are shallow-rooted plants, so during the growing season the potting soil should be kept moist, which is beneficial to plant growth. Because summer is relatively dry, the frequency of watering can be appropriately increased.
2. Light
China asters prefer a warm environment with plenty of sunlight, and grow vigorously in a well-ventilated spot with ample light.
China asters respond fairly sensitively to daylight and prefer sunlight exposure.
3. Temperature
The suitable growing temperature for China asters is 15°C—25°C. They have relatively weak cold tolerance and are not tolerant of intense heat.
In winter, the temperature must not fall below 3°C. If the temperature drops below 0°C, the stems and leaves will suffer frost damage.
In summer, if the temperature exceeds 30°C, China asters will produce fewer flowers or their flowering time will be delayed.
4. Soil
China asters like fertile, moist, well-drained soil. Generally, loam or sandy loam is chosen, and fertilizer is applied appropriately according to the plant's growth.
2. Precautions for Growing China Asters
1. Water moderately
Watering should be done according to actual conditions. The potting soil must not be too moist, otherwise China asters will grow leggy and lodge, and diseases may occur. Water accumulation caused by overwatering can also cause the roots of China asters to rot and the plants to die.
2. Maintain long hours of light
China asters like sunlight. If the daily exposure reaches 15 hours, the plants will grow vigorously and stay relatively short and sturdy, and the flowering period will also come earlier. Conversely, if the daylight hours are short, the plants will grow taller, and the flowering period will be correspondingly delayed.
Therefore, when growing them, place the plants in a spot where they can receive direct sunlight.
3. Prune the branches regularly
China asters do not need pinching, but in order to make the flowers on the main stem stand out, the side branches can be pruned regularly, keeping only 5—7 flowering branches per plant.
3. Pests and Diseases of China Asters and Their Control Methods
1. Yellows disease
Symptoms
Yellows disease is caused by infection with mycoplasma-like organisms (MLO). MLO mainly survives on various perennial hosts and is spread mainly by leafhoppers, dodder, and so on.
Yellows disease is the most serious disease of China asters. After infection, the leaves turn pale yellow, many broom-like branches grow, and the flower color gradually fades, turning pale yellow-green.
The entire plant becomes short and stunted, and its growth vigor weakens.
Control methods
It is best to grow the plants in a netted enclosure to prevent infection by the pathogen.
Insecticides such as 50% malathion 1000x solution or diazinon can be sprayed to control leafhoppers, thereby blocking transmission.
If China asters are infected with yellows disease, medical tetracycline or oxytetracycline 4000x solution can be sprayed for control.
2. Gray mold
Symptoms
This disease is likely to occur when China asters are growing in a high-humidity environment at 20°C, and it is a common disease of China asters.
Gray mold harms the flowers and leaves of China asters. In the early stage of infection, water-soaked yellow-green or dark green spots appear, and then the spots gradually expand. In the later stage, the flowers and leaves drop off and the plant withers and dies.
When the humidity in the environment is high, a gray powdery spore layer appears on the leaves.
Control methods
Be careful to place China asters in a ventilated spot, control environmental humidity, and avoid excessive water accumulation.
Once infected, promptly remove diseased plants and leaves, and spray 50% procymidone wettable powder 1500x solution or 50% iprodione 1500x solution.
3. Fusarium wilt
Symptoms
The pathogen is Fusarium oxysporum f. sp. callistephi, which can survive for many years on diseased plants and spreads via seeds and soil.
When infected, the whole plant wilts, the plant becomes dwarfed, the leaves turn black, the roots and stems rot, and pink or rose-colored masses of conidia appear at the base.
Control methods
Before sowing, soak the seeds in 0.1% mercuric chloride solution for 30 minutes to kill the pathogens they carry.
Rotate the seedling-raising and planting plots or flower pots every year. Because the pathogen on diseased plant residues spreads with the soil, avoid mixing infected soil into new soil during operations.
In the early stage of the disease, apply chemicals as a root drench or spray: 50% carbendazim wettable powder 500x, with 0.25 kg of solution per plant, once every 5—7 days, for 2—3 consecutive times.
You can also use 40% carbendazim suspension concentrate 400x solution, or 50% thiophanate-methyl wettable powder 400x solution, or 10% shuangxiaoling aqueous solution 200-300x solution, or 25.9% kangkuining 500x solution.
Agricultural antibiotic "120" at 100 ppm as a root drench also has a certain control effect. Root drenching with potassium permanganate 800-1500x solution is also acceptable.
4. Rust
Symptoms
When alternate host plants of the genus Pinus are present near China asters, the disease is likely to occur and become epidemic.
Chlorotic spots appear on the leaf surface, and round, pale yellow, powdery spore masses can be seen on the underside.
Control methods
In the early stage of the disease, spray 15% triadimefon wettable powder 1500x solution or 12.5% subaoli 3000x solution.
5. Brown spot
Symptoms
The disease is severe in July and August in the north.
After infection, in the early stage nearly circular purple-brown lesions of varying sizes appear on the leaves, then turn black or dark brown.
In the later stage, the center of the lesions turns light gray and fine small black dots appear. When there are many lesions on a leaf, the whole leaf turns yellow and dries up.
Control methods
Remove and destroy diseased leaves promptly when found.
Spray 50% carbendazim wettable powder 1000x solution, or 80% zineb wettable powder 500—700x solution, or 1% Bordeaux mixture, or 755 chlorothalonil 500x solution for control, spraying once every 7—10 days.