Detailed Explanation of the Causes of Huagu Formation and Cultivation Techniques

  Huagu ranks among shiitake mushrooms as the highest in quality and the most economically valuable. Because it has characteristics such as thick caps, a beautiful appearance with white radiating or chrysanthemum-shaped cracks, tender flesh, rich aroma, and abundant nutrition, it is deeply loved by consumers in domestic and international markets. At the same time, it is also the most competitive type among similar shiitake products. 

     I. Causes of Huagu formation.Huagu forms under special climatic conditions, especially in high-altitude areas, where it is most easily formed under conditions of low winter temperatures, dry air, and large temperature and humidity differences. Any shiitake variety can form Huagu as long as it has the specific environmental conditions mentioned above. The cracks on the surface of the Huagu cap are formed by unsynchronized cell division and growth between the surface and interior. The outermost surface cells of the cap divide and grow slowly at night under lower temperatures and during the day under dry air conditions. The internal flesh cells, however, divide and grow vigorously under conditions of relatively suitable moisture and temperature. As a result, the surface cells burst open and crack, forming white patterns. 

     II. Environmental conditions for Huagu formation.The formation of Huagu is the result of the combined influence of multiple environmental conditions such as temperature, humidity, temperature difference, humidity difference, and light. 

     1. Temperature. The varieties used for cultivating Huagu mostly belong to the low-temperature type or the medium-low temperature type, and the low-temperature ranges for their primordium differentiation and fruiting body development are 5-15°C and 5-18°C, respectively. Generally, when the monthly average temperature is 8-10°C and the day-night temperature difference is above 10°C, ideal Huagu can be formed. In the later stage of fruiting body growth, if there are 3-4 consecutive days with a day-night temperature difference above 14°C, Huagu can also be formed. The greater the temperature difference and the longer it lasts, the more obvious the cracks will be. 

     2. Humidity. Humidity is the key condition for Huagu formation. Humidity includes three aspects: the water content of the culture material in the fungus bags, the relative air humidity, and the humidity of the cultivation site. The water content of the culture material should preferably be slightly lower than that of conventional bag cultivation. Generally, the material-to-water ratio is 1:0.8-0.9, and it should not exceed 1:1. When the relative air humidity in the mushroom shed is below 70%, with 55-60% being optimal, Huagu can mostly be formed. The ground water evaporation at the cultivation site should be small, and the relative humidity above and below should all be under relatively consistent dry conditions, which is conducive to Huagu formation.
 
     3. Light. Light affects Huagu formation in two ways: first, it directly affects the color of the cap and the length of the stipe; second, it indirectly raises temperature, lowers humidity, and accelerates the drying of the surface of the mushroom buds. If mushroom buds are formed under dark conditions, the phenomena of small caps, long stipes, thin flesh, and light color will appear, making it difficult to form Huagu. Appropriately increasing light is beneficial to Huagu formation. Shading conditions should be changed from the traditional cultivation ratio of three parts light to seven parts shade to four parts light to six parts shade or five parts light to five parts shade. In the severe winter season, mushrooms can even be cultivated with full light. 

     4. Ventilation. While increasing temperature difference stimulation, maintaining dry air, and providing appropriate light, adding a dry gentle breeze (level 1-3) can deepen the cracks on the cap and keep the cracks white. 

     III. Site selection and mushroom shed setup.Generally, in high-altitude mountainous areas above 800 m, late autumn and winter have low temperatures, dry air, and large temperature and humidity differences, making them the best natural environment for Huagu formation. While making use of the advantages of the natural environment, choose mountain or flat land that is well ventilated, sunny, dry, and close to a water source as the site for cultivating Huagu. Set up a mushroom shed on the mushroom site, with a height of more than 2 m, using bamboo and wood as supports around it, using fir branches or branches with many twigs and few leaves as shading material on top, and using small bamboo, reeds, sugarcane leaves, etc. as surrounding curtains. The shading degree should preferably be four parts light to six parts shade. Inside the shed, set up tiered mushroom racks, each with 4-5 layers, mostly 5 layers. The top of the shed is fixed with arched bamboo strips and covered with plastic film. The plastic film hung around the mushroom racks can be raised and lowered flexibly. When the temperature is relatively low, lower the plastic film, leaving only a section at the bottom for ventilation. When the weather is clear, raise the plastic film to allow ventilation and air exchange, reduce humidity, and drain moisture. Starting in March, plant climbing beans (cowpea, green bean, etc.) and gourds (loofah, cucumber, winter melon, etc.) around the mushroom shed, which can both increase economic benefits and create an ecological environment in which shiitake mushrooms and crops benefit each other. 

     IV. Preparation of fungus bags and selection of strains.The inoculation period is mostly in early spring. Usually, February to April is the bag-making and inoculation period, and September to April of the following year is the fruiting period. The formula of the culture material is basically the same as that for conventional bag cultivation. Commonly used ones are: (1) 78% mixed wood sawdust, 20% wheat bran, 1% sucrose, 1% gypsum. (2) 77% mixed wood sawdust, 20% wheat bran, 1% sucrose, 1% gypsum, 0.5% urea, 0.5% superphosphate. The material-to-water ratio is 1:0.8-0.9, and it should not exceed 1:1. The material should be packed relatively firmly, generally with each bag of wet material weighing 2-2.2 kg. The selected strains should preferably be low-temperature type or medium-low temperature type varieties with relatively low water content in the fruiting body, large caps, thick flesh, short stipes, and large-leaf type, such as 135, 908, etc.