Freeze drying cannabis was made notable by Ed Rosenthal, author of the Marijuana Grower’s Handbook. He analyzed that by using the frost-free section of a home freezer, one can dry cannabis within 10 to 20 days.  This is possible since water sublimates from the frozen flower, turning directly from ice to water vapor without going through the liquid state. Rosenthal recommended commercial freezers for scaled operations and large paper bags to slow the evaporation for curing. 
Recently, freeze drying cannabis for commercial use was further developed by Rich DeLong, founder and operator of Botanique Preservation Equipment. When cannabis was medically legalized in Arizona where DeLong’s company is located, they set out to produce the best-looking flowers for packaging. Through some trial and error, DeLong combined low pressures and low temperatures (down to -85°F) for equipment that reduces the dry time to about 24 hours for up to 1,100 pounds.
Freeze dried cannabis maintains high cannabinoid and terpene content in addition to keeping its initial taste, color, and shape. In simple terms, it makes cannabis buds look a lot prettier for consumers. Freezing cannabis in general helps protect against temperature-related chemical degradation. Freeze drying also allows cannabis to enter the market more quickly.
However, what does all this mean in terms of extraction?
In states with legalized cannabis, there’s a massive demand for concentrates and cannabis vaping products. Some consumers want the highest tetrahydrocannabinol content they can get their hands on. This is part of the reason freeze drying has become so popular.
Though there have been other extraction methods used in creating cannabis concentrates, freeze dried flower with solvent extraction has become more of a standard as liquid live resin products gain in popularity. Live resin provides consumers with a product that’s both potent and flavorful, having better locked in terpenes that might otherwise have been lost during routine curing practices.
Challa et al estimate that the “cost of freeze drying is about four to ten times higher than that of convective hot air drying.”  However, demand for high-quality medicinal cannabis (e.g., live resin) makes it worthwhile.
- Rosenthal E. Marijuana Grower’s Handbook. Quick Trading Company, 2009.
- Challa, SKR, Misra NN, Martynenko A. “Drying of Cannabis—State of the Practices and Future Needs.” Drying Technology, 2020, pp.1–10, doi:10.1080/07373937.2020.1752230. [Journal Impact Factor = 2.307; Times Cited = N/A]