Blue agave is the most common source of agave syrup. It is extracted from the core of the plant in large doses. The blue agave is commonly referred to as "the century plant." Though it does not live a century, it can live for many years, but only flowers once in its lifetime. The nectar of the blue agave is harvested once the plant reaches full maturity at 10 years. The top of the plant is cut off and the nectar is extracted until it is empty. The blue agave can only be harvested once, as the extraction process kills the plant, even if it has never flowered.
For the Salmiana species of agave, the harvesting process is a little different than most other agaves. Flowering stalks on the plants are removed so that the sap that oozes from that area will continue to flow consistently. This sap can be collected twice per day. A natural enzyme is then used to change the carbohydrates in the syrup to sugars instead of using a heating process.
Green agave is a less common agave plant with a much lower concentration of fructose, making the amount of syrup that can be harvested smaller. Green agave produces raw agave nectar because of the low fructose concentration which makes it slightly less sweet, but with more nutrients. Green agave is found near the edges of deserts or close to water sources as they require more hydration than other types of agave.
There are other types of agaves including rainbow agave and thorny agave. The main difference between the various types of agaves is the concentration of fructose and the amount of agave nectar that can be processed from the raw plant. Depending on the type of agave that is harvested, the different types of syrup that can be produced include premium dark, premium light, standard light, standard dark, amber and raw syrup.