Traditionally shiitake has been grown on natural logs of various species of trees but currently oak (Quercus) logs are most popular.
Generally, logs of 7-15 cm dia are cut into 1m lengths. Holes are then drilled; one row of holes is drilled for each 2.5 cm of log diameter and are evenly spaced length-wise every 15 cm along the row.
Holes are plugged with wood piece spawn or sawdust spawn, and then finally sealed with hot wax; plug spawn is however preferred for varied reasons. Spawn run may take 6-18 months which depends upon many factors.
Logs, after the spawn-run, are transferred to a growing yard, which should be cooler and humid than the spawn-run area. One interesting treatment given to induce fruiting in logs is ‘shocking treatment’ where logs are banged with a hammer or dropped on end (Chang and Miles 1989).
Production is very good during the spring and fall. Some growers, however, use green houses for winter production when the prices are considerably higher. In the green house cultivation technology, logs are generally soaked in water and vibrated mechanically prior to keeping in the houses. After taking the first flush, logs are reincubated for about 3 months and the process is repeated upto five times. Yields obtained from log system may be as high as 33 %; best production occurs in second and third years. Shiitake production drops and is no longer possible after the bark is lost.
To make the shiitake cultivation more environment-friendly, synthetic log production system was developed where sawdust is the main ingredient; however, straw and corncobs are also used. Basal ingredients are supplemented with some starchy substance like cereal brans, maize and some chemicals like calcium carbonate, calcium sulfate (gypsum) and sugar. Ingredients are mixed in a mixer and moistened to a level of 60 per cent. Moistened substrate is generally filled in polypropylene bags (2.5 Kg). Little holes are either made in the polybags or special breather patch made of micro-porous plastic is preprovided. The bags are then sterilized for 2 h at 121'C in large autoclaves and, after cooling, seeded with spawn. The bags after heat sealing are shaken to evenly distribute the spawn; sawdust spawn or cereal grain spawn is used in this system. Spawn-run at 21'C with 4 hours of light per day takes 18-23 days for optimum growth. Colonised blocks are taken out by slicing and peeling off the polycover and kept for 4 weeks in the environment conducive for browning of the exterior surface i.e. temperature of about 19 oC and 2000-3000 ppm CO2and are watered once daily; only humidification may also be resorted to. As the browning process nears completion, pinheads start to form about 1-2 mm beneath the surface. Primordia development is stimulated by soaking the blocks in cool water (12 oC) for 3-4 hours; soaking is required for second and third flushes also. Mushrooms are ready for harvesting approximately after 7-11 days of soaking.
Mushrooms are harvested by gentle twisting by hand and stem cut with sharp knife like that for button mushroom. After harvesting, blocks are soaked again for 12 hours, which may be 18 hours in third soaking; flush breaks in shiitake are 16-20 days long. The total production cycle on synthetic logs is just 3-4 months and biological efficiency achieved is also very high (75 to 125 per cent) as against cycle of 5-6 years and B.E. of 33 % in natural log cultivation (Royse 2001).