Hey, like in my thread (Talking about the same island

).
I had plenty people look at Guams daylight hours, and this is how I understand it:
First of all from what other people have told me, A pure Sativa Strain would be good for this climate. I will be growing Thai Full Moon which is available on the Nirvana seed bank here:
http://www.nirvana-shop.com/en/full-moon-feminized-5-seeds.html
I guess in Guam we have a Short and Long season, The Long season starts around March which is when you ideally want to start planting. Yes, its under 12 hours but the plant WONT start flowering because Pure sativas take around 2 months to sexually mature, and by that time the daylight hours will already be nearing 13 hours a day so it wont start flowering but it will stay in vegetative phase until August which is when it will start to flower because the days will be getting shorter.
Then you'll harvest around Nov/Dec. That much time in the veg phase will probably bring the plant atleast 5 feet tall
The reason you dont plant in Jan or Feb is because if you plant that early it will be sexually mature and able to flower at around March/mid april and the daylight hours will still be short enough for it to go into flowering, then by May it will have to stop flowering because of longer days, making it revert back to veg which will delay plant growth I think.
Now, the short season I think starts around the time the long season plants start flowering so at about August. You'll plant in August then it will start flowering as soon as its able to since the daylight hours are shorter than 12 hours. then you'll harvest your Long season plants at around Oct/Nov, and then also harvest the short season plants around Dec/Jan.
The short season plants will have less yield, because of shorter veg time, but maybe if you planted more during the short season and used a high nitrogen fertilizer during veg phase you can get decent sized plants.
Feb would be prep month I guess for the next years long season. I think this is similar to how people grow on Hawaii, I'm not sure.
For growing Indicas, Veggie Gardener suggested that since Indicas are less sensitive to daylight changes that Indica plants might not even start flowering... And if that is the case then I guess autoflowering Northern Lights would be good

:
http://www.nirvana-shop.com/en/autoflower-strains/northern-light-feminized-autoflower-seeds.html
I think thats pretty much summed up growing weed on Guam outdoors. I believe that information is mostly correct.
Hope to see you on guam, happy growing.
EDIT: Another thing I forgot to mention, after August when the Long season plants SHOULD start flowering you can expose the plants to artificial lights to PREVENT flowering until October, then it will flower and finish around the same time as the short season plants. This may get even larger yield per plant. I may do this because I'm only starting to plant now, and its a little later than march.