Good seed can make a big differance in growth and yield.You didnt mention what growing medium you are using.Ie. dirt base,I have good results with a blend of peatmose8cups,perlite2cups,cottonburmulch2cups,betterearthcompost2cups,1tbls.asomite.The best seed I have found so far I got frome wheatgrassman.com.This seed has increased my yield by 30%.Im getting a 12oz. average per 11/21 inch trays.The average hieght is 11inchs.Good luck and happy growing!