Ed Rosenthal: Efficient Marijuana Cultivation Pt. I

January 19, 2017   

Marijuana has two main stages of growth: vegetative and flowering. Most varieties are “short-day plants” (sdp), and their stage of growth is determined by the number of hours of uninterrupted darkness the plants receive. Most varieties respond to a critical dark period (cdp) of at least10.5 hours by initiating flowering. Other popular sdp’s are chrysanthemums and poinsettias.

Using techniques based on cdp, growers can easily manipulate plants to grow vegetatively or to flower at any time of the year in a grow room, greenhouse or outdoors, weather permitting. Growers can use this to their advantage in many ways. Some examples:

Plants can be started early in the season and be kept growing vegetatively by interrupting the dark cycle several times daily using fluorescent, HPS, or red LEDs.

Plants can be forced to flower early in the summer rather than in the fall using light deprivation. Growers usually use a regimen of 12-12 light-darkness. Three advantages to this, (1) The buds receive more light when maturing in the summer rather than the fall so they grow bigger and have a higher quality, and (2) growers can beat the others to market, when prices are still high. (3) Plants can be manipulated to grow to the size you find most convenient.

When marijuana is forced to flower and ripen early several problems that often plague gardens are avoided. Buds that are initiated and ripen in summer are exposed to more light than autumn flowers, so they grow larger and more potent. Summer grown flowers aren’t affected as much by “weather”. 

Another advantage for greenhouse growers and cultivators in the southern and mid-tier states is that they can use light deprivation techniques to produce two to four crops per year.

GrowSpan makes it easy for you with its fully automated light deprivation greenhouses. A less expensive, but equally effective, method is to use row cover framing and white/black film to manually control light. With the light deprivation greenhouse, repeating timers are used in the system to break up the dark periods keeping plants from getting too long a period of uninterrupted darkness.

Come back on Tuesday, January 24 for Part II.