The prevailing opinion on picking morels is to pinch off the stems or to cut the stem with a knife. Most people believe that will not damage the hidden mycelium. After watching people pull the morels out of the ground and raking the area to find any small ones left behind. I have seen those areas no longer produce. I never pick all the morels from a producing area. I like to leave a percentage to mature and spore out form future harvesting. When I find old ones I will cut the stems and spread the heads around the area in an attempt to spread the spores around. The left behind stems will continue to grow.