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Abstract [Objectives] The aim was to study the artificial cultivation of Bletilla striata to realize large scale and standardization planting. [Methods] The comparison tests were conducted on B. striata with different canopy densities of the Magnolia officinalis forests， different compound planting densities and different tending measures and management. [Results] When the stand canopy density was 0.4-0.6， the per unit yield of B. striata was 5.4%， 6.8% higher than that at the canopy density of less than 0.4 and more than 0.6， respectively. When the planting density was 30 cm×30 cm， the per unit yield increased by 16.1%， 12.0%， 13.1% respectively compared with the planting density of 20 cm×20 cm， 25 cm×25 cm， 35 cm×35 cm. When B. striata was planted from October to November， the per unit yield was 5.6% higher than that planted from December to January of the following year， and 21.3% higher than that from February to March of the second year. When farmyard manure was applied during the cultivation， the per unit yield was 31.7% and 18.4% higher than the application of chemical fertilizer and compound fertilizer. When weeding 4 times per year， the per unit yield increased by 240.1%， 137.0% and 43.9% respectively from that weeding 1 times， 2 times， 3 times per year. [Conclusions] When planting B. striata， the stand canopy density of 0.4-0.6 could make it receive absolutely shelters and the lighting conditions required for the growth， thereby bringing in high emergence rate， good growth potential and high yield. The best planting effect of B. striata could achieve by planting from October to November with the planting density of 30 cm×30 cm， which can play the maximum benefit of individual plants. Moreover， weeding 4 times per year combined with the use of farmyard manure can promote the development and growth of tubers， which can greatly improve the yield of B. striata.
Key words Three gorge dam area； Bletilla striata； Compound planting under forest； Canopy densities； Tending measures
Bletilla striata （Thunb.） Reichb. f is a perennial herb in the orchid family Orchidaceae. Modern pharmacological studies have confirmed that B. striata contains ingredients such as starch， glucose， volatile oil， and mannan， and has a significant hemostatic effect. It can be used to treat pulmonary tuberculosis， bronchiectasis， hemoptysis， and bleeding of stomach and duodenal ulcers. In recent modern pharmacology studies， embolic agent of B. striata not only has no toxic and side effects， but also can promote blood coagulation， making it a good embolic agent. Moreover， it also has the effect of anti-inflammation and anti-tumor， having the dual role of embolization and chemotherapy[1-2]. In recent years， in addition to being used directly as a decoction slice， B. striata has also been made into emulsifier and suspending agent. It is also widely used in cosmetics and healthcare products. With the continuous reduction of the wild resources of B. striata， the output is declining year by year. However， the market demand of B. striata has been increasing in recent years and the prices have also been rising. It is expected that in the coming years， the gap between supply and demand will continue to widen， and the sales momentum will shift from the current best-selling to strong sales， and prices will also rise to a new level. Therefore， the introduction and domestication and standardized planting of B. striata have become the inevitable choices to solve the shortage of natural B. striata resources and improve the inherent quality of B. striata. Test Area Overview
The test area is located in Dongjiahe Village， Zhangcunping Town， Yiling District， Yichang City， Hubei Province in the Three Gorges Dam Region. The average elevation is about 1 000 m. The low-lying mountain basins and piedmont depressions are connected along the geological shape， presenting the continuous and intermittently reappearing complex landforms. The area has an average annual temperature of 12.5 ℃， extreme minimum temperature of -16.4 ℃， extreme maximum temperature of 37 ℃， 8-10 h of light time in spring and winter， 11-13 h in summer and autumn， frost-free period concentrated from May to October， and annual precipitation of about 1 200 mm. The rainfall distribution is 24.1% in spring （March to May）， 39.6% in summer （June to August）， 31.5% in autumn （September to November）， and 5.3% in winter （December to February）. In 2013， Dongjiahe Village set up the "Yichang Fumin B. striata Specialized Cooperative" with more than 1 million Yuan input in production， and the scale planting area of B. striata was 62.08 hm2， involving 562 households. The farmers picked the wild B. striata resources in forest to cultivate. After 3-4 years of artificial cultivation， it could have an average income of 200 000 Yuan per 666.7 m2. At present， B. striata has a promising market and has become a highly profitable industry with "small planting area producing great income". The test site was the reclaimed Magnolia officinalis forest with the stand density of 844 plants/hm2， average tree height of 6.5 m， and the average DBH of 6.3 cm. The slope of the forest was 10-15°. The soil was mainly yellow-brown soil derived from the differentiation of limestone， which was 40-60 cm thick with the pH of 6.9， and the soil was loose and fertile with sufficient sunlight and water.
Materials and Methods
Test materials
The seed stems of wild B. striata for the test were old stalks and tender shoots with no worms， no damages， no diseases and many buds. When planting， it was necessary to plant the 1-year-old seed stems and 2-4-year-old stems separately. The 1-year-old seed stems were directly put into field production， while the 2-4-year-old seed stems were concentrated to force buds and grow seedlings， and then transplanted into field after 1-2 years[3].
Test methods
Planting methods
B. striata seed stems were planted under the M. officinalis forest between plants （rows）. The soils were plowed at the depth of over 40 cm， and the well-prepared land was excavated into cabins that were about 100 cm wide and about 40 cm high. The seed stems were planted from October to January 2014， from December 2014 to January 2015， and from February to March 2015. When seeding， the seed stems with tender buds were cut into small pieces， each piece should have 1-2 buds， and 3-4 tubers were planted in each nest. The tubers were placed with the distance of 6-8 cm between each other. After the cuttings were stained with plant ash， the stems were spread at the bottom of the nest close to each other with the bud mouth outward staggered in triangle， and then the nests were filled with soil and compacted[4-5]. The stems were planted in the planting densities of nests of 20 cm × 20 cm， 25 cm × 25 cm， 30 cm × 30 cm， 35 cm × 35 cm； fertilizers included farmyard manure， chemical fertilizer and compound fertilizer； tillage weeding was conducted twice， 3 times and 4 times， respectively， to observe and record the growth and yield of B. striata in the sample plots. Survey Methods
The survey indicators included canopy density， emergence rate， growth potential and yield. In the test forest， 12 inspection lines were set up in each plot within the range of different stand canopy density to carry out general investigation to the 13.3 hm2 of the B. striata and M. officinalis compound planting forest. The site conditions， wood conditions of the test forest were investigated[6]， and the inspection was repeated for 24 times with the small class questionnaire recorded. Based on the site inspection， 9 plots of different canopy densities were set in the M. officinalis forest as the permanent sample plots according to the same management level and site conditions. The permanent sample plots were divided into the following types： canopy density of less than 0.4， canopy density of 0.4-0.6， and canopy density of more than 0.6. Each of the above type had 3 sample plots， and each sample plot had an area of 666.7 m2. In each plot， several control plots with area of 10 m2 were divided according to different planting density and management measures. From 2014 to 2016， a detailed investigation and record was made on the emergence rate， flowering period， growth potential， yield （fresh weight， dry weight） of B. striata， and the information was recorded in the "Statistical Table of Growth of B. striata of Different Planting Densities" and "Statistical Table of Growth of B. striata at Different Stand Canopy Densities" "Statistical Table of Growth of B. striata with Different Planting Time"， "Statistical Table of Growth of B. striata with Different Fertilizers" and "Statistical Table of Growth of B. striata with Different Weeding Times".
Data processing
Excel and SPSS were used to do the data statistics and variance analysis to the observed and recorded emergence rate， flowering time， growth potential and yield of B. striata.
Results and Analysis
Effect of canopy density on growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different stand canopy densities were observed and recorded in each of the control plot of the 9 permanent sample plots[7]， and the averages were taken. The results are shown in Table 1.
The plants of B. striata planted under the forest with the canopy density of 0.4-0.6 had the high emergence rate and good growth potential. The emergence rate was 4.3%， 7.2% higher than that planted at the canopy density of less than 0.4 and over than 0.6， respectively， while the average plant height was 11 cm， 14 cm higher than that planted at the canopy density of less than 0.4 and over than 0.6， respectively. The per unit yield （dry） of B. striata planted under the forest with the canopy density of 0.4-0.6 was 3 029 kg/hm2， which showed an increase of 5.4%， 6.8% from that planted at the canopy density of less than 0.4 and over than 0.6， respectively. The results suggested that stand canopy density had a significant effect on under-forest planting of B. striata. Planting at the canopy density of 0.4-0.6 could maximize the emergence rate， average plant height， growth potential and yield of B. striata planted under forest. Effect of planting density on growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different planting densities were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 2， first， the planting density of B. striata had a certain influence on the emergence rate， average plant height， and growth potential. Due to sunlight， moisture and other factors， with the decrease of planting density， that is， the increase of the nesting distance， the emergence rate increased， the plant height increased， and the growth potential became better. Second， the planting density of B. striata had great effect on its yield. The per unit yield of B. striata at the planting density of 30 cm × 30 cm was 3 461 kg/hm2， which was 16.1%， 12.0% and 13.1% higher than that at the planting densities of 20 cm × 20 cm， 25 cm × 25 cm， and 35 cm × 35 cm， respectively. Therefore， 30 cm × 30 cm is the best density for planting B. striata under the forest.
Effect of planting time on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different planting time were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 3， October-November was the best time to plant B. striata. The emergence rate of B. striata planted in October-November， 2014 was 1.8%， 4.7% higher than that planted in December， 2014–January， 2015 and February-March， 2015， while the average height was 11 cm， 23 cm higher than that planted in December， 2014–January， 2015 and February-March， 2015， respectively. In terms of yield， B. striata planted in October-November， 2014 had a yield of 3 420 kg/hm2， and the unit area yield was 5.6% and 21.3% higher than that planted in December， 2014–January， 2015 and February-March， 2015. The results indicated that the winter planting of B. striata should be early， which could have corresponding early emergence， high emergence rate， good growth potential and high yield.
Effect of fertilization types on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata applied with different fertilizers were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 4， the application of farmyard manure had the best effect in cultivating B. striata. The application of farmyard manure to B. striata could make it had good growth potential performance， and the average height was 14 cm， 7 cm higher than that applied with chemical fertilizer， compound fertilizer， respectively. The yield （dry） of B. striata applied with farmyard manure was 4 545 kg/hm2， and the yield per unit area was 31.7%， 18.4% higher than that applied with chemical fertilizers， compound fertilizer， respectively. Moreover， the observation also found that farmyard manure had the best effect， but there were significant differences between different farmyard manure， and the effect was the best using sheep excrement， followed by cow dung. Effect of intertillage weeding times on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata applied with different weeding times were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 5， 4 times of weeding during the cultivation of B. striata had the best effect. The results showed that the B. striata with 4 times a year of weeding had excellent growth potential， and the average plant height was 33 cm， 23 cm， 12 cm higher than that with 1 times， 2 times， 3 times a year. The yield （dry） of B. striata with 4 times a year of weeding was 4 230 kg/hm2， and the yield per unit area increased by 240.1%， 137.0%， and 43.9%， respectively， compared to the unit area yield of B. striata with 1 times， 2 times， 3 times a year. It is advisable to conduct weeding for 1 times in early May， early July， early August and late September throughout the growth cycle of B. striata， which will benefit the growth and development of B. striata. Moreover， the intertillage weeding should be shallow， and the surface soil should be loosened with weeds thoroughly removed.
Conclusions and Discussions
（1） Stand canopy density is an important factor affecting the emergence rate， plant height growth， growth potential and yield of B. striata planted under M. officinalis forest. The test results showed that when the stand canopy density was 0.4-0.6， the emergence rate was high， the growth potential was good， and the yield was high， and when the canopy density was lower than 0.4 or higher than 0.6， the performances of emergence rate， growth potential， and yield of B. striata were relatively poorer. The reason is that when the canopy density is too low， it cannot provide proper shading for the growth of B. striata， and when the canopy density is too large， it cannot satisfy the light conditions needed for the later growth of B. striata. Therefore， the stand canopy density of 0.4-0.6 is favorable to the increase of yield of B. striata， which is the most suitable canopy density for planting B. striata.
（2） Different planting densities also have great effects on the emergence rate， growth potential and yield of B. striata. The test results showed that with the increase of nesting distance， the emergence rate increased and the growth potential became better. The yield at the planting density of 30 cm × 30 cm was the highest. If the planting density is too large， it will affect the growth of plant height and diameter， which cannot play the greatest benefit of individual plants， and it needs more seed stems， requiring for greater costs. If the planting density is too low， it cannot make full use of the land resources， failing to achieve the best economic efficiency. In summary， the best planting density （nesting distance） is 30 cm × 30 cm to plant B. striata under forest. （3） Different planting time leads to great differences in the emergence rate， growth potential and yield of B. striata. The plants of B. striata planted in October-November had high emergence rate， good growth potential and high yield. Thus， winter planting of B. striata should be early， which could have corresponding early emergence， high emergence rate， good growth potential and high yield.
（4） The application of farmyard manure has the best effect in cultivating B. striata. Compared with the application of chemical fertilizers， compound fertilizers， the application of farmyard manure makes B. striata have better growth potential and higher yield. The application of farmyard manure during the cultivation of B. striata can loosen soil， enhance the permeability of soil， and promote the development and growth of tubers of B. striata.
（5） The yield of B. striata can be greatly increased by weeding 4 times a year. Weeding for 1 times in early May， early July， early August and late September throughout the growth cycle of B. striata can benefit the growth and development of B. striata， and greatly increase the yield.
References
[1] LIN FL， YANG CY， YANG WW， et al. A survey of the modern research of the traditional Chinese medicine Bletilla striata[J]. Chinese Journal of Hospital Pharmacy， 2013， 33（7）： 571-573.
[2] Editorial board of Chinese Herbal of the State Administration of Traditional Chinese Medicine. Chinese herbal[M]. Shanghai： Shanghai Science and Technology Press， 1994：327.
[3] ZHANG M. Artificial breeding technology of wild Bletilla striata[J]. Modern Agricultural Science and Technology， 2016（16）：79.
[4] ZHANG YC. Biological characteristics and cultivation techniques of Bletilla striata[J]. Information of Agricultural Science and Technology， 2007， （11）： 45.
[5] LIU WB. Imitation of wild planting of Bletilla striata[J].Yunnan Agriculture，2016（6）：27-28.
[6] LIU YJ， YIN GM. Investigation of wild Bletilla formosana striata resources in Baoshan and feasibility analysis of artificial cultivation[J]. Journal of Baoshan Teachers College， 2014， 5（33）： 25-27.
[7] LIAN XC. Artificial cultivation techniques of Bletilla striata under the crown of Chinese fir plantation[J]. China Agricultural Information. 2014（6）：09.
Key words Three gorge dam area； Bletilla striata； Compound planting under forest； Canopy densities； Tending measures
Bletilla striata （Thunb.） Reichb. f is a perennial herb in the orchid family Orchidaceae. Modern pharmacological studies have confirmed that B. striata contains ingredients such as starch， glucose， volatile oil， and mannan， and has a significant hemostatic effect. It can be used to treat pulmonary tuberculosis， bronchiectasis， hemoptysis， and bleeding of stomach and duodenal ulcers. In recent modern pharmacology studies， embolic agent of B. striata not only has no toxic and side effects， but also can promote blood coagulation， making it a good embolic agent. Moreover， it also has the effect of anti-inflammation and anti-tumor， having the dual role of embolization and chemotherapy[1-2]. In recent years， in addition to being used directly as a decoction slice， B. striata has also been made into emulsifier and suspending agent. It is also widely used in cosmetics and healthcare products. With the continuous reduction of the wild resources of B. striata， the output is declining year by year. However， the market demand of B. striata has been increasing in recent years and the prices have also been rising. It is expected that in the coming years， the gap between supply and demand will continue to widen， and the sales momentum will shift from the current best-selling to strong sales， and prices will also rise to a new level. Therefore， the introduction and domestication and standardized planting of B. striata have become the inevitable choices to solve the shortage of natural B. striata resources and improve the inherent quality of B. striata. Test Area Overview
The test area is located in Dongjiahe Village， Zhangcunping Town， Yiling District， Yichang City， Hubei Province in the Three Gorges Dam Region. The average elevation is about 1 000 m. The low-lying mountain basins and piedmont depressions are connected along the geological shape， presenting the continuous and intermittently reappearing complex landforms. The area has an average annual temperature of 12.5 ℃， extreme minimum temperature of -16.4 ℃， extreme maximum temperature of 37 ℃， 8-10 h of light time in spring and winter， 11-13 h in summer and autumn， frost-free period concentrated from May to October， and annual precipitation of about 1 200 mm. The rainfall distribution is 24.1% in spring （March to May）， 39.6% in summer （June to August）， 31.5% in autumn （September to November）， and 5.3% in winter （December to February）. In 2013， Dongjiahe Village set up the "Yichang Fumin B. striata Specialized Cooperative" with more than 1 million Yuan input in production， and the scale planting area of B. striata was 62.08 hm2， involving 562 households. The farmers picked the wild B. striata resources in forest to cultivate. After 3-4 years of artificial cultivation， it could have an average income of 200 000 Yuan per 666.7 m2. At present， B. striata has a promising market and has become a highly profitable industry with "small planting area producing great income". The test site was the reclaimed Magnolia officinalis forest with the stand density of 844 plants/hm2， average tree height of 6.5 m， and the average DBH of 6.3 cm. The slope of the forest was 10-15°. The soil was mainly yellow-brown soil derived from the differentiation of limestone， which was 40-60 cm thick with the pH of 6.9， and the soil was loose and fertile with sufficient sunlight and water.
Materials and Methods
Test materials
The seed stems of wild B. striata for the test were old stalks and tender shoots with no worms， no damages， no diseases and many buds. When planting， it was necessary to plant the 1-year-old seed stems and 2-4-year-old stems separately. The 1-year-old seed stems were directly put into field production， while the 2-4-year-old seed stems were concentrated to force buds and grow seedlings， and then transplanted into field after 1-2 years[3].
Test methods
Planting methods
B. striata seed stems were planted under the M. officinalis forest between plants （rows）. The soils were plowed at the depth of over 40 cm， and the well-prepared land was excavated into cabins that were about 100 cm wide and about 40 cm high. The seed stems were planted from October to January 2014， from December 2014 to January 2015， and from February to March 2015. When seeding， the seed stems with tender buds were cut into small pieces， each piece should have 1-2 buds， and 3-4 tubers were planted in each nest. The tubers were placed with the distance of 6-8 cm between each other. After the cuttings were stained with plant ash， the stems were spread at the bottom of the nest close to each other with the bud mouth outward staggered in triangle， and then the nests were filled with soil and compacted[4-5]. The stems were planted in the planting densities of nests of 20 cm × 20 cm， 25 cm × 25 cm， 30 cm × 30 cm， 35 cm × 35 cm； fertilizers included farmyard manure， chemical fertilizer and compound fertilizer； tillage weeding was conducted twice， 3 times and 4 times， respectively， to observe and record the growth and yield of B. striata in the sample plots. Survey Methods
The survey indicators included canopy density， emergence rate， growth potential and yield. In the test forest， 12 inspection lines were set up in each plot within the range of different stand canopy density to carry out general investigation to the 13.3 hm2 of the B. striata and M. officinalis compound planting forest. The site conditions， wood conditions of the test forest were investigated[6]， and the inspection was repeated for 24 times with the small class questionnaire recorded. Based on the site inspection， 9 plots of different canopy densities were set in the M. officinalis forest as the permanent sample plots according to the same management level and site conditions. The permanent sample plots were divided into the following types： canopy density of less than 0.4， canopy density of 0.4-0.6， and canopy density of more than 0.6. Each of the above type had 3 sample plots， and each sample plot had an area of 666.7 m2. In each plot， several control plots with area of 10 m2 were divided according to different planting density and management measures. From 2014 to 2016， a detailed investigation and record was made on the emergence rate， flowering period， growth potential， yield （fresh weight， dry weight） of B. striata， and the information was recorded in the "Statistical Table of Growth of B. striata of Different Planting Densities" and "Statistical Table of Growth of B. striata at Different Stand Canopy Densities" "Statistical Table of Growth of B. striata with Different Planting Time"， "Statistical Table of Growth of B. striata with Different Fertilizers" and "Statistical Table of Growth of B. striata with Different Weeding Times".
Data processing
Excel and SPSS were used to do the data statistics and variance analysis to the observed and recorded emergence rate， flowering time， growth potential and yield of B. striata.
Results and Analysis
Effect of canopy density on growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different stand canopy densities were observed and recorded in each of the control plot of the 9 permanent sample plots[7]， and the averages were taken. The results are shown in Table 1.
The plants of B. striata planted under the forest with the canopy density of 0.4-0.6 had the high emergence rate and good growth potential. The emergence rate was 4.3%， 7.2% higher than that planted at the canopy density of less than 0.4 and over than 0.6， respectively， while the average plant height was 11 cm， 14 cm higher than that planted at the canopy density of less than 0.4 and over than 0.6， respectively. The per unit yield （dry） of B. striata planted under the forest with the canopy density of 0.4-0.6 was 3 029 kg/hm2， which showed an increase of 5.4%， 6.8% from that planted at the canopy density of less than 0.4 and over than 0.6， respectively. The results suggested that stand canopy density had a significant effect on under-forest planting of B. striata. Planting at the canopy density of 0.4-0.6 could maximize the emergence rate， average plant height， growth potential and yield of B. striata planted under forest. Effect of planting density on growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different planting densities were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 2， first， the planting density of B. striata had a certain influence on the emergence rate， average plant height， and growth potential. Due to sunlight， moisture and other factors， with the decrease of planting density， that is， the increase of the nesting distance， the emergence rate increased， the plant height increased， and the growth potential became better. Second， the planting density of B. striata had great effect on its yield. The per unit yield of B. striata at the planting density of 30 cm × 30 cm was 3 461 kg/hm2， which was 16.1%， 12.0% and 13.1% higher than that at the planting densities of 20 cm × 20 cm， 25 cm × 25 cm， and 35 cm × 35 cm， respectively. Therefore， 30 cm × 30 cm is the best density for planting B. striata under the forest.
Effect of planting time on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata at different planting time were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 3， October-November was the best time to plant B. striata. The emergence rate of B. striata planted in October-November， 2014 was 1.8%， 4.7% higher than that planted in December， 2014–January， 2015 and February-March， 2015， while the average height was 11 cm， 23 cm higher than that planted in December， 2014–January， 2015 and February-March， 2015， respectively. In terms of yield， B. striata planted in October-November， 2014 had a yield of 3 420 kg/hm2， and the unit area yield was 5.6% and 21.3% higher than that planted in December， 2014–January， 2015 and February-March， 2015. The results indicated that the winter planting of B. striata should be early， which could have corresponding early emergence， high emergence rate， good growth potential and high yield.
Effect of fertilization types on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata applied with different fertilizers were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 4， the application of farmyard manure had the best effect in cultivating B. striata. The application of farmyard manure to B. striata could make it had good growth potential performance， and the average height was 14 cm， 7 cm higher than that applied with chemical fertilizer， compound fertilizer， respectively. The yield （dry） of B. striata applied with farmyard manure was 4 545 kg/hm2， and the yield per unit area was 31.7%， 18.4% higher than that applied with chemical fertilizers， compound fertilizer， respectively. Moreover， the observation also found that farmyard manure had the best effect， but there were significant differences between different farmyard manure， and the effect was the best using sheep excrement， followed by cow dung. Effect of intertillage weeding times on the growth of B. striata
The emergence rate， average height， growth potential and yield of B. striata applied with different weeding times were observed and recorded in each of the control plot of the 9 permanent sample plots， and the averages were taken.
As shown in Table 5， 4 times of weeding during the cultivation of B. striata had the best effect. The results showed that the B. striata with 4 times a year of weeding had excellent growth potential， and the average plant height was 33 cm， 23 cm， 12 cm higher than that with 1 times， 2 times， 3 times a year. The yield （dry） of B. striata with 4 times a year of weeding was 4 230 kg/hm2， and the yield per unit area increased by 240.1%， 137.0%， and 43.9%， respectively， compared to the unit area yield of B. striata with 1 times， 2 times， 3 times a year. It is advisable to conduct weeding for 1 times in early May， early July， early August and late September throughout the growth cycle of B. striata， which will benefit the growth and development of B. striata. Moreover， the intertillage weeding should be shallow， and the surface soil should be loosened with weeds thoroughly removed.
Conclusions and Discussions
（1） Stand canopy density is an important factor affecting the emergence rate， plant height growth， growth potential and yield of B. striata planted under M. officinalis forest. The test results showed that when the stand canopy density was 0.4-0.6， the emergence rate was high， the growth potential was good， and the yield was high， and when the canopy density was lower than 0.4 or higher than 0.6， the performances of emergence rate， growth potential， and yield of B. striata were relatively poorer. The reason is that when the canopy density is too low， it cannot provide proper shading for the growth of B. striata， and when the canopy density is too large， it cannot satisfy the light conditions needed for the later growth of B. striata. Therefore， the stand canopy density of 0.4-0.6 is favorable to the increase of yield of B. striata， which is the most suitable canopy density for planting B. striata.
（2） Different planting densities also have great effects on the emergence rate， growth potential and yield of B. striata. The test results showed that with the increase of nesting distance， the emergence rate increased and the growth potential became better. The yield at the planting density of 30 cm × 30 cm was the highest. If the planting density is too large， it will affect the growth of plant height and diameter， which cannot play the greatest benefit of individual plants， and it needs more seed stems， requiring for greater costs. If the planting density is too low， it cannot make full use of the land resources， failing to achieve the best economic efficiency. In summary， the best planting density （nesting distance） is 30 cm × 30 cm to plant B. striata under forest. （3） Different planting time leads to great differences in the emergence rate， growth potential and yield of B. striata. The plants of B. striata planted in October-November had high emergence rate， good growth potential and high yield. Thus， winter planting of B. striata should be early， which could have corresponding early emergence， high emergence rate， good growth potential and high yield.
（4） The application of farmyard manure has the best effect in cultivating B. striata. Compared with the application of chemical fertilizers， compound fertilizers， the application of farmyard manure makes B. striata have better growth potential and higher yield. The application of farmyard manure during the cultivation of B. striata can loosen soil， enhance the permeability of soil， and promote the development and growth of tubers of B. striata.
（5） The yield of B. striata can be greatly increased by weeding 4 times a year. Weeding for 1 times in early May， early July， early August and late September throughout the growth cycle of B. striata can benefit the growth and development of B. striata， and greatly increase the yield.
References
[1] LIN FL， YANG CY， YANG WW， et al. A survey of the modern research of the traditional Chinese medicine Bletilla striata[J]. Chinese Journal of Hospital Pharmacy， 2013， 33（7）： 571-573.
[2] Editorial board of Chinese Herbal of the State Administration of Traditional Chinese Medicine. Chinese herbal[M]. Shanghai： Shanghai Science and Technology Press， 1994：327.
[3] ZHANG M. Artificial breeding technology of wild Bletilla striata[J]. Modern Agricultural Science and Technology， 2016（16）：79.
[4] ZHANG YC. Biological characteristics and cultivation techniques of Bletilla striata[J]. Information of Agricultural Science and Technology， 2007， （11）： 45.
[5] LIU WB. Imitation of wild planting of Bletilla striata[J].Yunnan Agriculture，2016（6）：27-28.
[6] LIU YJ， YIN GM. Investigation of wild Bletilla formosana striata resources in Baoshan and feasibility analysis of artificial cultivation[J]. Journal of Baoshan Teachers College， 2014， 5（33）： 25-27.
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