When To Harvest Your Medical 
    Marijuana Cannabis Plants?

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. 

0) Maturity and THC

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 actual ly contain more THC
than the females (Frank and Rosenthal, Marijuana Grower’s Guide, p. 66). 
Even connoisseurs 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)

1) Plant Size

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. 

2) Photoperiod – The Key to Maturation

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 (vegetative) 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 respond
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. 

3) Male Versus Female

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. 

4) Different Varieties

Many gardeners report that certain cannabis varieties take longer to
mature than others.  In particular, the narrow-leafed Sativa are said to
take significantly longer to initiate and complete budding, as compared to
the wide-leafed Indicas.  Under some conditions, Sativa will require an
additional month or more to mature after the Indicas have been harvested. 

5) Time of Year

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 time.  In the Fall, once the length of
day drops below 12 hours, the count-down to harvest will be begin. 
Weather conditions 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. 

6) Monitoring Buds

The best way to tell if the plant is ready is to examine the bud.  In the
paragraphs below, the terms "pistil" 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 pot 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 variable