There were many warehouses where the herbs were stored. This was a necessary part of the peak since most of the herbs took a long time to grow. Thus if they wanted a sufficient quantity and a stable supply, they needed to grow a lot of them at once.
Even the low grade spirit herbs needed few months to years to grow. While those that were of high grade would even need centuries to grow. Currently, the herbs that Lin Mu was seeing everywhere, were of either low grade or mid grade herbs.
These herbs were not as valuable as high grade herbs and did not have growth conditions that were as strict as those for the high grade herbs. The high grade herbs were grown in specific gardens that were well controlled by the elders of the peak.