Outdoors EARLY FLOWERING -(sexing)

Most marijuana plants cultivated in the United States begin to flower by late August to early October and the plants are harvested from October to November. For farmers in the South, parts of the Midwest, and West Coast, this presents no problem and no special techniques and instructions are needed for normal flowering.
In much of the North and high-altitude areas, many varieties will not have time to complete flowering before fall frosts. To force the plants to flower earlier, give them longer night periods. If the plants are in containers, you can simply move them into a darkened area each evening.

Plants growing in the ground can be covered with an opaque tarpaulin, black sheet plastic, or double or triple-layers black plastic trash bags. Take advantage of any natural shading because direct sunlight is difficult to screen completely. For instance, if the plants are naturally shaded in the morning hours, cover the plants each evening or night. The next morning you uncover the plants at about eight to nine o'clock. Continue the treatment each day until all the plants are showing flowers. This usually takes two weeks at most, is the plants are well developed (about four months old). For this reason, where the season starts late, it is best to start the plants indoors or in cold frames and transplant outdoors when the weather is mild. This in effect lengthens the local growing season and gives the plants another month or two to develop.

By the end of August the plants are physiologically ready to flower; they sometimes do with no manipulation of the photoperiod. More often female plants show a few flowers, but the day-length prevents rapid development to large clusters. The plants seem in limbo - caught between vegetative growth and flowering. The natural day-length at this time of year will not be long enough to reverse the process, so you can discontinue the treatment when you see that the new growth is predominantly flowers.
In areas where frosts are likely to occur by early October, long-night treatments may be the only way you can harvest good-sized flower clusters. These clusters, or buds, are the most potent plant parts and make up the desired harvest. Forcing the plants to flowers early also means development while the weather is warm and the sun is shining strongly.

The flower buds will form much faster, larger and reach their peak potency. A good time to start the treatments is early to middle August. This allows the plants at least four weeks of flowering while the weather is mild.
Another reason you may want to do this is to synchronize the life cycle of the plants with the indigenous vegetation. In the northeast and central states, the growing season ends quite early and much of the local vegetation dies back and changes color. Any marijuana plants stick out like green thumbs, and the crop may get ripped off or busted. Plants treated with long nights during late July will be ready to harvest in September.

Outdoor growers should always plant several varieties, because some may naturally flower early, even in the northern-most parts of the country. These early-maturing varieties usually come from Mexican, Central Asian, and homegrown sources. By planting several varieties, many of you will be able to find or develop an early-maturing variety after a season or two. This, of course, is an important point, because it eliminates the need for long-night treatments.





Preventing Flowers

Manipulation of the photoperiod can also prevent the plants from flowering until a desired time. For example, in Hawaii the weather is mild enough to grow winter crops. The normal summer crop is harvested anytime from September to mid-November. The winter crop is generally planted from October to December. Because the winter days are so short, the plants flower almost immediately, usually within two month. The plants are harvested in their third or fourth month and yield about 1/4 the yield of summer plants.

A large Hawaiian female can yield a pound of buds. Most of the plant's overall size is reached while it is vegetatively growing. By interrupting the night period with light, you can keep these plants vegetatively growing for another month, yielding plants of about twice the size.
The amount of light needed to prevent flowering is quite small (about .03 foot candles95 - on a clear night the full moon is about .01 foot candles). However, each plant mist is illuminated fully, with the light shining over the whole plant.

This might be accomplished with either electric light or a strong flashlight. The easiest way is to string incandescent bulbs, keeping them on a timer. The lights need be turned on for only a flash at any time during the night period, from about 9:00 PM to about 3:00 am. The interrupts the long night period to less then nine hours. Start these night treatments each night or two, until you want the plants to flower.


This info was brought from greenmanspage.com

holy shit I know this is ancient, but how did NO one comment on this? AMAZING explaination and description, exactly what I'm looking for since I'll be growing this outdoors in New England:

http://www.youtube.com/watch?v=iA4oo6o8BMY

please let me know if you have any pointers for sativa dominants or this plant exclusively.



thanks again man. +rep

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it seems to me that no matter what strain i grow. they all show preflowers after 3 weeks to 1 1/2 month old. i always thought that they wouldnt show untill they got the 12 dark. but uh uh

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D.A.R.E. to keep kids off drugs: translation: Does Anyone Really Expect-------- to keep kids off drugs
http://www.rollitup.org/grow-journal...rain-grow.html

this is a very detailed and well said explanation. but how long does it take for outdoor plants to start showing sex? im just starting my first grow from bagseed and want to make sure i get rid of males before they pollinate my fems. right now the biggest plant has about 5 nodes, but i cant find anything to identify its sex.

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GET HIGH!

Some people confuse Pre-Flower with the Start of Flower.

Pre Flower is when the plant reaches Sexual Maturity. This happens at about a month to 2 months old.

You can tell Sex when plants have reached this level of Maturity by looking at the pre flowers at the node.

Flowering will happen when the plant gets 14 to 12 hours of daylight. And you will see the start of flowers at the end of the branches.

Early sexing is done by checking the preflowers, not the start of flowering.

So you dont have to force a plant to flower to tell what sex it is. You just have to grow it to a healthy sexual maturity.

I can sex my entire crop just after summer solstice.

This year iam gonna try to have some Clones ready to go in the holes where the males used to live.

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"The greatest service which can be rendered to any country is to add a useful plant to its culture." - Thomas Jefferson

I used a 100w cfl to prevent my plants from flowering I raised above them for the first 4 mounths from 9pm till 12am, I had it set on a timer to go on and off every day, then when they're of good siz I take the big ones in to the "Dark Room" (Is also outside) So I can grow year round to supply myself with some nice buds, and I when the real seaon comes I set the timer off and turn it on after the season.

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<_-CANinBIZ-_>

Great info i'll be using this since I live up in Canada and i got a few white widow seeds from a friend.

Bump...

Good method. An old hippi method is to put your plant in 3 days of COMPLETE darkness. after the third night bring it back out, it should show signs of sexing in about a week if you did it right. If any light interupts the 3 day dark period it will not work as well.