The closest thing to fresh plants is freeze drying. Yet it even concentrates all aspect of the plant as many pounds of plants are needed to produce one pound of powder. Enzymes and antioxidants are concentrated many fold as well. Other methods, like air drying etc., have active constituents of the plants lost.
The process of freeze drying (lyophilization for the hi-tech crowd) involves harvesting the plants at their peak. They are then washed in fresh spring water and sprayed clean.The cleaned plants are immediately frozen to provide for the necessary conditions for low temperature drying. The plants are then placed under a vacuum. This enables the frozen water in the herb to vaporize without passing through the liquid stage, a process known as sublimination. Low temperature condenser plates remove the vaporized water from the vacuum chamber by converting it back to a solid. This completes the separation process.
After the vacuum has been introduces there is about 4-5% of moisture left in the plant material. To reduce this final moisture content, low temperature heat is applied to the frozen material to accelerate sublimation and pull off the remaining moisture.