A method for raising seedlings of Viola cornuta to enhance its frost resistance in the northern region

Abstract

A seedling raising method for improving the frost resistance of Viola cornuta in the northern region, comprising the following steps: Step 1, preparation work; Step 2, sowing; Step 3, management during the seedling stage; Step 4, management after transplanting seedlings; Step 5, field planting. The present invention provides a seedling raising method for improving the frost resistance of Viola cornuta in the northern region. This method can improve the frost resistance of Viola cornuta, enabling it to overwinter in the open field in the plain area north of the Yangtze River. Specifically, the present invention controls the time nodes, cultivation technical points, and management technical points in the cultivation and application processes such as sowing, seedling management, potting and field planting of Viola cornuta, so as to improve the overwintering ability of Viola cornuta, thereby realizing overwintering in the open field in the plain area north of the Yangtze River Basin.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural planting, and specifically relates to a seedling raising method for improving the frost resistance of Viola cornuta in the northern region. Background Art

[0002] Viola cornuta L., a perennial herbaceous plant of the genus Viola in the Violaceae family. It is native to Spain and the Pyrenees Mountains and is cultivated throughout China. Viola cornuta likes a cool climate. It can be sown in autumn and applied to spring flower beds, or sown in summer and bloom in late autumn. It is currently the main flower used in early spring flower beds, flower borders, and courtyard greening in areas north of the Yangtze River such as Qingdao.

[0003] The suitable temperature for sowing and germination of Viola cornuta is 20±2°C, and the suitable temperature for seedling growth is 16±2°C. A suitable day-night temperature difference is beneficial to seedling growth and seedling development. Viola cornuta seeds have a photophobic germination property and are easy to germinate in a relatively dark environment with a high germination rate. After emergence, they like sunlight and can tolerate partial shade. Seedling growth is afraid of waterlogging. The seedling-raising substrate requires good drainage and is a fertile, acidic substrate rich in organic matter, with the most suitable pH value being 5.5-6.0.

[0004] As a herbaceous flower with strong cold resistance, rich flower colors, and lovely shapes, Viola cornuta has been widely used in urban landscape greening. However, it cannot overwinter in the open ground north of the Yangtze River Basin, or the above-ground part will wither during the coldest periods of the year. The reason why the existing planting methods cannot enable Viola cornuta to be planted and overwinter in the open ground is that the growth potential of the seedlings before overwintering is insufficient, the lignification degree of the roots is not high enough, and the fibrosis degree of the stems and leaves is not high enough. In order to improve the cold resistance of Viola cornuta, the seedling raising method needs to be improved. Summary of the Invention

[0005] The present invention provides a seedling raising method for improving the frost resistance of Viola cornuta in the northern region. This method can improve the frost resistance of Viola cornuta and enable it to overwinter in the open ground in the plain areas north of the Yangtze River. Specifically, the present invention controls the time nodes, cultivation technical points, and management technical points in the cultivation and application processes such as sowing, seedling management, potting, and open-ground planting of Viola cornuta to improve the overwintering ability of Viola cornuta, thereby achieving open-ground planting and overwintering in the plain areas north of the Yangtze River Basin.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A seedling raising method for improving the frost resistance of Viola cornuta in the northern region includes the following steps:

[0008] Step 1, Preparation work;

[0009] Step 2, Sowing;

[0010] Step 3, Seedling stage management;

[0011] Step 4. Management after transplanting seedlings;

[0012] Step 5. Field planting.

[0013] Preferably, step 1 includes the following steps:

[0014] 1.1 Seedling-raising substrate: Select the substrate. When mixing the substrate soil, spray carbendazim 800 times liquid to disinfect the substrate; Use clean water to increase the humidity of the substrate soil to the extent that when clenched in the hand, no water overflows from the finger seams, it forms a ball when held, and scatters when released;

[0015] 1.2 Select a seedling-raising plug tray: Soak the plug tray in carbendazim 800 times liquid for 5 - 10 minutes for disinfection before use;

[0016] 1.3 Fill the plug tray with soil: Fill the prepared substrate soil into the plug tray, level it with a flat plate, and spray fine mist to thoroughly moisten it until water seeps out from the bottom of the plug tray;

[0017] 1.4 Fine sand on the ground: Spread fine sand evenly on the ground or the raised bed in the solar greenhouse, and spray carbendazim 800 times liquid to disinfect the greenhouse;

[0018] 1.5 Drainage system control: The drainage facilities around the solar greenhouse should be in good operation, and there should be no water accumulation in the greenhouse.

[0019] Preferably, in step 1.1, the substrate uses peat soil, and the weight ratio is peat: perlite: vermiculite = 7:3:1; In step 1.2, the viola uses coated seeds, and the seedling-raising plug tray selects a 200-hole plug tray or a 128-hole plug tray.

[0020] Preferably, step 2 includes the following steps:

[0021] 2.1 Select the sowing time in early September and complete sowing before the autumnal equinox solar term;

[0022] 2.2 Sow with a seeding machine into the plug tray, and set the sowing depth not exceeding 1 / 3 of the plug tray depth;

[0023] 2.3 Place the sown plug trays neatly in a single layer on the raised bed or separately on the ground (Xi: colloquial, same as raised bed. Place them separately, and the Xi should be flat but not necessarily covered with fine soil like the raised bed); After sowing, avoid placing the plug trays in the air or stacking them in multiple layers;

[0024] 2.4 Before watering, cover the whole Xi with tertiary vermiculite to seal the sowing opening with vermiculite, and the thickness should be appropriate to cover the seeds, about 2 - 3 mm (after sowing the seeds, there will be a sowing opening above, which needs to be sealed with vermiculite. Generally, it will be automatically sealed when watering for the first time); The tertiary vermiculite needs to increase humidity in advance, and spray water to make up for the loss of humidity after covering; Cover the whole plug trays with a film tightly, and press the film edge with fine sand; No watering is required before the viola germinates;

[0025] 2.5 Shading: The method is as follows: Add a double-layer shading net with an internal shading rate of 80% in the greenhouse or adopt the method of lowering the greenhouse insulation quilt for shading.

[0026] 2.6 Ventilation: Ventilate from 10:00 to 15:00 every day, and adjust the ventilation time according to the temperature in the greenhouse.

[0027] Preferably, in step 2.6, when the temperature in the greenhouse is lower than 18°C, shorten the ventilation time; when the temperature in the greenhouse is higher than 25°C, extend the ventilation time.

[0028] Preferably, step 3 includes the following steps:

[0029] 3.1 Temperature control: The suitable temperature for the sowing and germination of Viola cornuta is 20±2°C. When the temperature > 25°C or < 15°C, its germination speed slows down and the germination rate decreases; when the temperature > 30°C or < 10°C, germination stops. Make effective use of the characteristics of the solar greenhouse to increase temperature during the day and keep warm at night, control the temperature during the germination period, and maintain the temperature required for the seedling raising of Viola cornuta;

[0030] 3.2 Seedling emergence management: When the seedlings emerge 0.5 - 0.7 cm, uncover the film; when the seedlings grow 2 - 3 true leaves and the height is about 1 - 1.5 cm, remove the shading net, keep ventilation during the day, and the humidity in the shed should not be higher than 85%; if the temperature in the shed is higher than 35°C, shade with a 50% single-layer shading net;

[0031] 3.3 Prevention of damping-off disease: When the seedlings of Viola cornuta are in the high-temperature and high-humidity period, the probability of damping-off disease is relatively high, and prevention needs to be strengthened. First, control water and fertilizer and increase light to prevent excessive growth, improve the quality of seedlings, and enhance disease resistance; second, use drugs for prevention. When the seedlings of Viola cornuta grow two true leaves, use Dingmiaoxin, once every 7 - 10 days;

[0032] 3.3 Water and fertilizer management: Observe the moisture condition of the substrate every day, and keep the humidity in the shed not exceeding 50%; the EC value of the water is ≤0.65 ms / cm, and the PH is ≤6.5; when the seedlings grow 1 - 2 true leaves, apply 20-10-20 nitrogen, phosphorus, and potassium compound fertilizer with a concentration of 50 PPM every 10 days; when growing to 3 - 4 true leaves, foliar fertilizer can be sprayed; control water and temperature, control the temperature at 15 - 20°C, and promote the plant to be strong by increasing light to prevent excessive growth;

[0033] 3.4 Node length control: Observe the stem elongation length during the growth process of Viola cornuta, and control the node length at 0.4 - 0.6 cm; if the elongation exceeds 0.8 cm, on the existing basis, reduce the frequency of water and fertilizer application, increase light, and reduce temperature and humidity. When it is difficult to lower the temperature, uncover all the films of the insulation greenhouse. When two consecutive nodes are greater than 0.7 cm, spray a 1500-fold solution of metronidazole once.

[0034] Preferably, step 4 includes the following steps:

[0035] 4.1 Transplanting: When the seedlings grow to 5 or 6 true leaves, transplant them into pots. For individual seedlings with weaker growth vigor, the potting can be postponed for 3 - 5 days. Select nutrient bowls with a diameter of 8 - 10 cm (if the pot diameter is greater than 10 cm, the final frost resistance ability will be reduced to varying degrees) and with more than 5 holes at the bottom. Use garden soil for the soil, and add 1 kg of compound fertilizer per cubic meter of soil to increase fertility.

[0036] When transplanting, first water the potting soil thoroughly, poke a small hole with a wooden stick of appropriate size, then plant the plug seedlings in the small hole, and water again. Place them under a 30% sunshade net for seedling recovery and transition within the first week after transplanting.

[0037] 4.2 Prevention of root rot: Disinfect and pre - mix the soil or substrate with a 1000 - fold solution of 40% Benfuracarb wettable powder for disinfection and prevention. When the disease is found, spray or irrigate the diseased plants with a 1000 - fold solution of 40% Benfuracarb wettable powder or drench the roots with a 1500 - fold solution of 8% 402 emulsifiable concentrate.

[0038] 4.3 Water and fertilizer management: The amount of water should not be too large. Water thoroughly once when the soil is completely dry, and then water again when it dries out next time. Regularly spray foliar fertilizers and water - soluble fertilizers on the roots, once a week, and control the ratio of N, P, and K. Select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a dilution of 2000 - 3000 times. For the third fertilization, use Paenibacillus polymyxa to promote root growth.

[0039] 4.4 Flower removal: Early flowers consume a large amount of nutrients, which is not conducive to winter nutrient storage. Remove all the flower buds before November, and start keeping the flowers after November.

[0040] Preferably, step 5 includes the following steps:

[0041] 5.1 Outdoor planting time: From late November to early December, it is advisable to be about 10 days after the local frost appears. The best planting time is from 10:00 to 15:00, and all should be planted before sunset.

[0042] 5.2 Planting key points: After leveling the site, carry out planting and apply sufficient base fertilizer. When planting, do not remove the pot, only leave enough holes at the bottom of the pot.

[0043] 5.3 Watering: After planting, pour 2 times of antifreeze water, and make sure it is thoroughly watered, with the water penetration depth more than 300 mm. Water again before freezing, and do not water during the winter frozen period. In mid - late February of the next year, water thoroughly, and start watering when it is dry in March (reduce the frequency on rainy days, and water when the dry depth of the surface soil is greater than 1 cm in principle).

[0044] 5.4 Fertilization: Apply organic fertilizer to the soil before planting. Do not fertilize during the winter frozen soil period. Start topdressing at the beginning of March of the following year. As the temperature rises and the violas enter the rapid growth stage, regularly spray foliar fertilizer and water-soluble fertilizer on the roots once a week. Control the ratio of N, P, and K. Select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a dilution of 2000 - 3000 times.

[0045] The seedling raising method for improving the frost resistance of violas in the northern region of the present invention has the following beneficial effects:

[0046] 1. Improve the frost resistance of violas, enabling them to be planted outdoors for wintering in the plain areas north of the Yangtze River and south of 37° north latitude.

[0047] 2. Use a sunlight greenhouse for seedling raising. During the cultivation process, make full use of the characteristics of the sunlight greenhouse to control and adjust temperature, light, etc., reducing the cultivation cost. It is more suitable for small-scale operations by farmers and lowers the threshold of large-scale production.

[0048] 3. Make effective use of the idle period of farmers' land in autumn during the cultivation nodes, increasing economic benefits and promoting the enthusiasm of farmers for production, and solving the problem of surplus labor of flower farmers in autumn.

[0049] 4. Expand the application scope of violas in autumn and winter, and partly solve the shortage of flower varieties for winter landscaping in the northern region.

[0050] 5. This technology is easy to operate and convenient to promote. However, it must be operated strictly in accordance with the methods and nodes of the technical content, otherwise the wintering effect cannot be achieved. Specific Embodiments

[0051] The following description details the embodiments of the present invention in a step-by-step manner. This description is only for the preferred embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

[0052] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", etc. is only for describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, specific orientation structure, and operation. Therefore, it should not be construed as a limitation of the present invention.

[0053] In the initial embodiment, the seedling raising method for improving the frost resistance of violas in the northern region of the present invention includes the following steps:

[0054] Step 1. Preparation work;

[0055] Step 2. Sowing;

[0056] Step 3. Seedling stage management;

[0057] Step 4. Management after transplanting seedlings;

[0058] Step 5. Field planting.

[0059] In a further embodiment, the said Step 1 includes the following steps:

[0060] 1.1 Seedling substrate: Select the substrate. When mixing the substrate soil, spray carbendazim solution at 800 times dilution to disinfect the substrate; Use clean water to increase the humidity of the substrate soil to the extent that when clenched in the hand, no water overflows from the finger joints, it forms a ball when held, and scatters when released; This is beneficial to seed germination, facilitates filling the substrate into the plug tray, and is easy to thoroughly water the seedlings after emergence.

[0061] 1.2 Select a seedling plug tray: Soak the plug tray in carbendazim solution at 800 times dilution for 5 - 10 minutes for disinfection before use.

[0062] 1.3 Fill the plug tray with soil: Fill the prepared substrate soil into the plug tray, level it with a flat plate, and spray fine mist to thoroughly moisten it until water seeps out from the bottom of the plug tray; Spraying water is beneficial for the substrate to be reasonably compacted and provides all the water required during the germination period.

[0063] 1.4 Fine sand on the ground: Spread fine sand evenly on the ground or the seedbed in the solar greenhouse, and spray carbendazim solution at 800 times dilution to disinfect the greenhouse.

[0064] 1.5 Drainage system control: The drainage facilities around the solar greenhouse should be in good operation, and there should be no waterlogging in the greenhouse.

[0065] In the said Step 1.1, the substrate uses peat soil (peat moss), and the weight ratio is peat: perlite: vermiculite = 7:3:1; In the said Step 1.2, the viola uses coated seeds, and the seedling plug tray selects a 200 - hole plug tray or a 128 - hole plug tray.

[0066] In a further embodiment, the said Step 2 includes the following steps:

[0067] 2.1 Select the sowing time in early September and complete sowing before the autumnal equinox solar term.

[0068] 2.2 Sow with a seeding machine into the plug tray, and the sowing depth does not exceed 1 / 3 of the plug tray depth.

[0069] 2.3 Place the sown plug trays neatly in a single layer on the seedbed or separately on the ground; After sowing, avoid placing the plug trays in the air or stacking them in multiple layers.

[0070] 2.4 Before watering, cover the entire mat with grade 3 vermiculite (use vermiculite to seal the sowing opening), with a thickness of about 2-3 mm to cover the seeds (after sowing, there will be a sowing opening on the top, which needs to be sealed with vermiculite. Generally, it will be automatically sealed when watering for the first time); the grade 3 vermiculite needs to be moistened in advance, and spray to replenish water if the moisture is lost after covering; cover the entire mat with film tightly, and press the edge of the film with fine sand; there is no need to water before the pansy germinates;

[0071] 2.5 Shading: Viola seeds germinate in the dark and require shading in a solar greenhouse. This can be achieved by adding a double-layer shade net with an 80% shading rate or by lowering a greenhouse blanket.

[0072] 2.6 Ventilation: Ventilate from 10:00 to 15:00 every day, and adjust the ventilation time according to the temperature in the greenhouse.

[0073] In step 2.6, if the temperature in the greenhouse is lower than 18°C, the ventilation time is shortened; if the temperature in the greenhouse is higher than 25°C, the ventilation time is extended.

[0074] In a further embodiment, step 3 comprises the following steps:

[0075] The seedling stage refers to the stage from when the pansy sprouts and the film is removed to when it is divided into pots and planted. The pansy can germinate 7-10 days after sowing and can be divided into pots and planted 30-40 days later.

[0076] 3.1 Temperature control: The optimum temperature for Viola sowing and germination is 20±2℃. If the temperature is >25℃ or <15℃, the germination speed will slow down and the germination rate will decrease. If the temperature is >30℃ or <10℃, germination will stop. Effectively utilize the characteristics of solar greenhouses that increase temperature during the day and keep warm at night to control the temperature during the germination period and maintain the temperature required for Viola seedling cultivation.

[0077] 3.2 Seedling management: 0.5-0.7cm after the seedlings emerge from the soil, uncover the film; when the seedlings grow 2-3 true leaves and are about 1-1.5cm high, remove the shade net. Keep ventilation during the day and the humidity in the greenhouse should not be higher than 85%; if the temperature in the greenhouse is higher than 35℃, use a 50% single-layer shade net for shade.

[0078] 3.3 Preventing Damping-off: The main prevention measures for viola seedlings are to control water and fertilizer and increase light to prevent excessive growth, improve seedling quality, and enhance disease resistance. Secondly, use medication for prevention. When the viola seedlings grow two true leaves, apply Ding Miao Xin (4.23% formamide, 1500 times dilution of ipconazole) every 7-10 days.

[0079] 3.3 Water and Fertilizer Management: Observe the moisture condition of the substrate every day, and keep the humidity in the greenhouse not exceeding 50%; the EC value of the water is ≤ 0.65 ms / cm, and the pH is ≤ 6.5; when the seedlings grow 1 - 2 true leaves, apply 20 - 10 - 20 nitrogen, phosphorus, and potassium compound fertilizer with a concentration of 50 PPM every 10 days; when it grows to 3 - 4 true leaves, foliar fertilizer can be sprayed; control the water and temperature, and control the temperature at 15 - 20 °C to make the plants strong by increasing light and prevent excessive growth;

[0080] 3.4 Internode Length Control: Observe the internode elongation length of the stem during the growth process of Viola cornuta, and control the internode length at 0.4 - 0.6 cm; if the internode elongation exceeds 0.8 cm, on the existing basis, reduce the frequency of water and fertilizer application, increase light, and reduce temperature and humidity. When it is difficult to lower the temperature, fully uncover the plastic film of the insulation greenhouse. When two consecutive internodes are greater than 0.7 cm, spray a 1500 - fold solution of metronidazole once.

[0081] In a further embodiment, step 4 includes the following steps:

[0082] 4.1 Transplanting: When the seedlings grow to 5 or 6 true leaves, transplant them into pots. For individual seedlings with weak growth potential, the potting can be postponed for 3 - 5 days; select a nutrient bowl with a pot diameter of 8 - 10 cm (if the pot diameter is greater than 10 cm, the final frost resistance will be reduced to varying degrees) and with more than 5 holes at the bottom. Use garden soil for the soil, add 1 kg of compound fertilizer (ternary compound N:P:K = 15:15:15) per cubic meter of soil to increase fertility;

[0083] When transplanting, first pour the potting soil thoroughly, make a small hole with a wooden stick of appropriate size, then plant the plug seedling in the small hole and water again. This can improve the survival rate of the seedlings during transplantation and shorten the seedling - recovery time. Keep them under a 30% sunshade net for seedling recovery and transition within the first week after transplantation;

[0084] 4.2 Prevention of Root Rot: At the initial stage of the root rot of Viola cornuta seedlings, the symptoms are not obvious. As the root rot worsens, the leaves wilt, the root bark turns brown and separates, resulting in the death of the whole plant. Disinfect and pre - mix the soil or substrate with a 1000 - fold solution of 40% Benfuracarb wettable powder for prevention; when the disease is found, spray or irrigate the diseased plants with a 1000 - fold solution of 40% Benfuracarb wettable powder or drench the roots with a 1500 - fold solution of 8% 402 emulsifiable concentrate;

[0085] 4.3 Water and Fertilizer Management: The amount of water should not be too large. Water thoroughly once the water is completely dry, and then water again after the next complete dryness; regularly spray foliar fertilizer and water - soluble fertilizer on the roots, once a week. Control the ratio of N, P, and K, and select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a concentration of 2000 - 3000 times. Use Paenibacillus polymyxa for the third fertilization to promote root growth;

[0086] 4.4 Flower picking: Early flowers consume a large amount of nutrients, which is not conducive to wintering nutrient reserves. All flower buds before November should be removed, and flowers should be retained after November.

[0087] In a further embodiment, step 5 includes the following steps:

[0088] 5.1 Outdoor planting time: From late November to early December, it is advisable to be about 10 days after the local frost appears. The best planting time is from 10:00 to 15:00, and all should be planted before sunset;

[0089] 5.2 Planting key points: After the site is leveled, plant and apply sufficient base fertilizer. Do not remove the pot during planting, only leave enough holes at the bottom of the pot;

[0090] 5.3 Watering: After planting, pour 2 times of anti-freezing water, and it should be poured thoroughly, with the water penetration depth into the soil greater than 300 mm; pour once again before freezing, and no watering is required during the winter frozen soil period; pour thoroughly in mid-to-late February of the following year, and start watering when it is dry in March (reduce the frequency on rainy days, and the principle is to water when the surface soil is dry to a depth greater than 1 cm);

[0091] 5.4 Fertilization: Apply organic fertilizer to the soil before planting, and do not fertilize during the winter frozen soil period. Start topdressing in early March of the following year; as the temperature rises and the violas enter the rapid growth period, regularly spray foliar fertilizer and water-soluble fertilizer on the roots, once a week. Control the ratio of N, P, and K, and select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a dilution of 2000 - 3000 times.

[0092] The mechanism of the present invention to improve the wintering ability of violas: During the cultivation process, accurately control the season, temperature, humidity, soil moisture, fertility, etc. at the key growth nodes of violas, and cooperate with key technologies such as flower picking and shortening the internode distance of the stem. Before wintering, increase its growth potential, improve the lignification degree of the roots, improve the fibrosis degree of the stems and leaves, improve the plant's ability to retain moisture and control temperature, and make the whole plant strong and compact, so that it can safely overwinter when planted on land.

Claims

1. A seedling raising method for improving the frost resistance of Viola cornuta in the northern region, characterized by including the following steps: Step 1, Preparation work; Step 2, Sowing; Step 3, Management during the seedling stage; Step 4, Management after transplanting seedlings; Step 5, Field planting; The said Step 3 includes the following steps: 3.1 Temperature control: The suitable temperature for the germination of Viola cornuta seeds is 20±2°C. When the temperature > 25°C or < 15°C, the germination speed slows down and the germination rate decreases; when the temperature > 30°C or < 10°C, germination stops. Make effective use of the characteristics of the solar greenhouse to increase temperature during the day and keep warm at night, control the temperature during the germination period, and maintain the temperature required for the seedling raising of Viola cornuta. 3.2 Seedling emergence management: When the seedlings emerge 0.5 - 0.7 cm, uncover the film; when the seedlings grow 2 - 3 true leaves and the height is 1 - 1.5 cm, remove the shading net, keep ventilation during the day, and the humidity in the shed should not be higher than 85%; when the temperature in the shed is higher than 35°C, shade and cool down with a 50% single-layer shading net. 3.3 Prevention of damping-off: When the Viola cornuta seedlings are in the period of high temperature and high humidity, the probability of damping-off is relatively high, and prevention needs to be strengthened; first, control water, fertilizer and increase light to prevent excessive growth, improve the quality of seedlings and enhance disease resistance; second, use drugs for prevention. When the Viola cornuta seedlings grow two true leaves, use Dingmiaoxin, once every 7 - 10 days. 3.4 Water and fertilizer management: Observe the moisture condition of the substrate every day, and keep the humidity in the shed not exceeding 50%; the EC value of water ≦ 0.65 ms / cm, PH ≦ 6.5; when the seedlings grow 1 - 2 true leaves, apply 20 - 10 - 20 nitrogen, phosphorus and potassium compound fertilizer with a concentration of 50 PPM every 10 days; when growing to 3 - 4 true leaves, foliar fertilizer can be sprayed; control water and temperature, control the temperature at 15 - 20°C, and promote the plant to be strong by increasing light to prevent excessive growth. 3.5 Node length control: Observe the stem elongation length during the growth process of Viola cornuta, and control the node length at 0.4 - 0.6 cm; if the elongation exceeds 0.8 cm, on the existing basis, reduce the frequency of water and fertilizer application, increase light, and reduce temperature and humidity; when it is difficult to reduce the temperature, lift all the films of the heat preservation greenhouse; when two consecutive nodes are greater than 0.7 cm, spray a 1500-fold solution of metronidazole once.

2. As described in claim 1, a seedling raising method for improving the frost resistance of Viola cornuta in the northern region, characterized in that the said Step 1 includes the following steps: 1.1 Seedling raising substrate: Select the substrate. When mixing the substrate soil, spray carbendazim 800-fold solution to disinfect the substrate; use clean water to increase the humidity of the substrate soil to the extent that when holding it tightly in the hand, no water overflows from the finger joints, it forms a ball when held, and scatters when released. 1.2 Select a seedling raising plug tray: Soak the plug tray in 800-fold solution of carbendazim liquid for 5 - 10 minutes for disinfection before use. 1.3 Fill the plug tray with soil: Fill the prepared substrate soil into the plug tray, level it with a flat plate, and spray fine mist to soak the water until the bottom of the plug tray shows water seepage. 1.4 Fine sand on the ground: Spread fine sand on the ground or the seedbed in the solar greenhouse to level the ground, and spray 800-fold solution of carbendazim to disinfect the shed. 1.5 Drainage system control: The drainage facilities around the solar greenhouse should operate well, and there should be no water accumulation in the shed.

3. The seedling raising method for improving the frost resistance of Viola cornuta in the northern region according to claim 2, characterized in that, In step 1.1, the substrate is mainly peat soil, and the weight ratio is peat: perlite: vermiculite = 7:3:1; in step 1.2, viola cornuta uses coated seeds, and the seedling tray is selected from a 200-hole tray or a 128-hole tray.

4. The seedling raising method for improving the frost resistance of Viola cornuta in the northern region according to claim 3, characterized in that, Step 2 includes the following steps: 2.1 The sowing time is selected in early September and the sowing is completed before the autumnal equinox solar term. 2.2 The seeder sows in the seedling tray, and the set sowing depth does not exceed 1 / 3 of the seedling tray depth. 2.3 The sown seedling trays are directly and neatly placed in a single layer on the raised bed or separately placed on the ground; after sowing, the seedling trays should be avoided being placed overhead or in multiple layers. 2.4 Before watering, cover the whole bed with grade 3 vermiculite to seal the sowing openings with vermiculite, and the thickness should be appropriate to cover the seeds; the grade 3 vermiculite needs to increase the humidity in advance, and if the humidity is lost after covering, spray water to make up; cover the whole bed of seedling trays tightly with a film, and press the film edge with fine sand; no watering is required before viola cornuta germinates. 2.5 Shading: The method is: add a double-layer shading net with an internal shading rate of 80% in the greenhouse or use the method of lowering the greenhouse insulation quilt for shading. 2.6 Ventilation: Ventilate from 10:00 to 15:00 every day, and adjust the ventilation time according to the temperature in the greenhouse.

5. The seedling raising method for improving the frost resistance of Viola cornuta in the northern region according to claim 4, characterized in that, In step 2.6, when the temperature in the greenhouse is lower than 18 °C, shorten the ventilation time; when the temperature in the greenhouse is higher than 25 °C, extend the ventilation time.

6. The seedling raising method for improving the frost resistance of Viola cornuta in the northern region as described in claim 5, characterized in that, Step 4 includes the following steps: 4.1 Transplanting: When the seedlings grow to 5 or 6 true leaves, transplant them into pots. For individual seedlings with weak growth potential, the potting can be postponed for 3-5 days; select a nutrient bowl with a pot diameter of 8-10 cm and more than 5 holes at the bottom. If the pot diameter is greater than 10 cm, the final frost resistance will be reduced to varying degrees. Use garden soil for the soil, add 1 kg of compound fertilizer per cubic meter of soil to increase fertility. When transplanting, first water the potting soil thoroughly, poke a small hole with a wooden stick of appropriate size, then plant the seedling tray in the small hole, and then water. Place it under a 30% sunshade net for acclimatization and transition within the first week after transplanting. 4.2 Prevent root rot: Disinfect and pre-mix the soil or substrate with a 1000-fold solution of 40% root rot ning WP for disinfection and prevention; when diseases are found, spray or irrigate the diseased plants with a 1000-fold solution of 40% root rot ning WP or drench the roots with a 1500-fold solution of 8% 402 EC. 4.3 Water and fertilizer management: The amount of water should not be too large. Water thoroughly once when the water is completely dry, and then water again when it is dry next time; regularly spray foliar fertilizer and water-soluble fertilizer on the roots once a week; control the ratio of N, P, and K, and select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a dilution of 2000-3000 times; use polymyxa bacillus for the third fertilization to promote root growth. 4.4 Flower removal: The early flowers consume a large amount of nutrients, which is not conducive to wintering nutrient reserves. All the flower buds before November are removed, and flowers are left starting from November.

7. The seedling raising method for improving the frost resistance of Viola cornuta in the northern region as described in claim 6, characterized in that, Step 5 includes the following steps: 5.1 Outdoor planting time: From late November to early December, it is appropriate about 10 days after the local frost appears. The best planting time is from 10:00 to 15:00, and all should be planted before sunset. 5.2 Planting key points: After the site is leveled, plant and apply sufficient base fertilizer. When planting, do not remove the pot, only leave sufficient holes at the bottom of the pot; 5.3 Watering: After planting, pour 2 times of anti-freezing water, and make sure to soak thoroughly, with the water penetrating more than 300 mm deep into the soil; water once again before freezing, and do not water during the frozen period in winter; pour thoroughly in mid-to-late February of the following year, start watering when the surface soil is dry from March, reduce the frequency on rainy days, and water when the dry depth of the surface soil is greater than 1 cm in principle; 5.4 Fertilization: Apply organic fertilizer to the soil before planting, do not fertilize during the frozen period in winter, and start topdressing at the beginning of March of the following year; as the temperature rises and the viola enters the rapid growth period, regularly spray foliar fertilizer and water-soluble fertilizer on the roots, once a week; control the ratio of N, P, and K, and select fertilizers with a mass ratio of N:P:K = 20:10:20 and N:P:K = 13:40:13, and apply them alternately at a dilution of 2000 - 3000 times.