Disclaimer: The author does not condone any illegal activity. The facts presented do not necessarily represent the opinion of the author. Mr.Brown -- 10/15/94.
The question of when to harvest tenderly cared-for plants is a question that puzzles many new growers. Most farmers' goal is to pluck the fruit at the exact moment when the potency of the bud is at is peak. Realistically, the skills needed to detect the specific day (or even hour) when a plant is at its peak can only be acquired through years of experience. However, even the novice grower should be able detect the window of time during which the harvest results in premier crop of outstanding bud.
Although some growers are interested in fiber content, most people consider the plant to be mature when the percentage of THC found in the plant reaches its maximum. It is not practical for the average grower to actually measure THC in a plant, as the chemistry is somewhat complex. In a growing plant, each successive pair of leaves contains more THC than the previous pair. The budding tips of the plant contain the most THC of all. Both male and female plants contain THC. In fact, some research has shown that in the early stages of growth the males actually contain more THC than the females (Frank and Rosenthal, Marijuana Grower's Guide, p. 66). Even conniseurs believe it is worth cutting and sampling shoots before the THC has reached its maximum. Clarke suggests that the best bioassy for pot is to roll joints of several different strains, invite all your friends over, and see which pile of joints disappears first (Marijuana Botany, p. 94)
The size of the plant has little to do with its maturity. Outdoors, a plant might reach a height of over eight feet (2.5m) and still not be ready for harvest. Indoors, mature, budding plants can be under 18" (.5m) high.
The chronological age of the plant has little to do with its maturity. How quickly a plant matures is mostly dependent on the amount of light the plant receives each day (photoperiod). Typically, a plant will transition from the growing (vegitative) stage to the budding stage when the light per day drops below 12 hours. This is not to say that a 3-week-old seedling will begin to bloom when the light is cut. As a general rule, a plant must be a minimum of 60 days old before it is mature enough to respo nd appropriately to decreased light. For indoor growers, the decision on when to cut the photoperiod depends on available growing space, as well as the need to harvest weed. Some growers report that clones (cuttings) can be forced to bloom prior to 60 days old, perhaps since the cutting itself is somewhat mature at the time it is rooted.
Almost always, male flowers will show prior to female buds. Thus, once the males in the garden are detected, you can be sure that that the female budding process will start soon - usually within 1-2 weeks.
Many gardeners report that certain cannibis varieties take longer to mature than others. In particular, the narrow-leafed Sativas are said to take significantly longer to initiate and complete budding, as compared to the wide-leafed Indicas. Under some conditions, Sativas will require an additional month or more to mature after the Indicas have been harvested.
Obviously, indoor growers cannot use the seasons as a guide to harvesting (though a cold winter-time grow room can significantly retard the growth of the plants). Outdoor growers on the other hand can use the seasons as a predictor of the ideal harvest t ime. In the Fall, once the length of day drops below 12 hours, the count-down to harvest will be begin. Weather conditons will affect the exact harvest day from year to year, but generally you can expect to harvest within the same two-week window each year. If you can avoid it, don't harvest during or immediately after a rainy spell.
The best way to tell if the plant is ready is to examine the bud. In the paragraphs below, the terms "pistal" and "stigma" refer to the white hairs in the center of the female bud. The term "calyx" refers to the pod that would surround the seed (were the plant to be fertilized). Many growers elect to pick each bud individually, as it reaches it prime.
"Buds are at their peak potency about one week after flower formation slows...Harvest the plants when about half the stigmas in the buds have withered... When the plants are left in the ground, the resinous qualities of the plant may become more apparent. The bracts and tiny leaves may swell in size...The resin content of these buds may be higher, [but] the grass will smoke more harshly than if the buds were younger when picked." Frank and Rosenthal Marijuana Growers Guide pg 289, pg 295.
"In the primordial calyxes the pistils have turned brown; however, all but the oldest of the flowers are fertile and the floral clusters are white...Many cultivators prefer to pick some of their strains during this stage in order to produce marijuana with a clear cerebral, psychoactive effect." Robert Connell Clarke Marijuana Botany, pg 140.
"Eventually the pistils start to turn color from pale white to red or brown...When the glands have swelled and the pistil has receded into the false pod, the bud is ready to pick." Ed Rosenthal, The Closet Cultivator, pg 100.
"At the peak of florescence, all but the oldest of flowers have white pistil development...Another indicator is bouquet. When a plant is at the peak of florescence, it has a sweet and musky fragrance. Later, it loses the sweetness." Kayo, The Sinsemilla Technique, pg 125.
"The best way to harvest is to examine the resin glands on each bud. As they turn from clear to amber, that is the optimum time to pick. Buds usually mature from the top down, if grown under artificial light, and you will end up with more high-quality p ot if you pick each bud when ready. However, the plant will not just continue to produces buds at the same rate. Like any other plant, the flowering cycle lasts a specific period of time. If you wanted a further harvest of buds, the plant would need a second cycle of vegetative growth. This can be achieved indoors by simply turning the lights back up to a 24 hour cycle for a few weeks. Outdoors though, you are dependent on the seasons. Frost and long nights will usually kill the plant. Of course, such a strategy is only viable
if growing a few plants. If your operation runs on an industrial scale, just drive the combine harvester through the field." (-peter alt.hemp posting)