How long would a plant take to flower from seed if you started it growing in a greenhouse from about now?
Right now the days are still very short, but we are past the peak of winter so the days are slowly getting longer again. You can look up sunrise and sunset charts for your local area to see how long the days will be. currently rounding it off you are looking at about 11hrs sunlight per day so a newly planted seed will grow for maybe 2 or 3 weeks and then try to flower (while growing a bit more at the same time).
Just a plant in say a 250mm pot so not that big. Also , would the yield be bigger getting natural light compared to indoor with the same size plant? ( say 2 ounces off the indoor plant )
250mm pot sounds fair to me. If it gets good light, the plant is only going to have 4 or 5 nodes before it tries to flower (strain dependent of course) so you can imagine it will only be small. Some people that '12-12 from seed' (as they call it when you plant a seed under flowering light hours, usually indoor) can get 2 ounces from one plant apparently. But be ready for some strains/conditions to yield you as little as a 1/4 ounce. Not even the weather man does a good job of guessing the weather so we can't tell you if it will be as good as artificial lighting. Technically under optimum conditions (no cloud, etc) the outdoor light is superior in quality and depth penetration. Where as an indoor plant will get popcorn crap down the bottom, outdoor light is just as bright on the tip of a plant as it is on the dirt sitting next to it on the ground (HID light halves intensity with ever 30cm distance).
Also , what is a good nutrient brand? I just feed mine 'Miracle Grow' I know it's not that great but my local bunnings does not have that much of a selection.
Don't top dress a small potted plant, especially with such a short and hungry life cycle. It won't reach the plant in time unless it's already in there ready to go before the plant arrives. I would recommend trying to make your own soil because it will be tons cheaper and far superior. Check out the ROLs thread for good info but as a basic guide, if you used 1 part earth worm compost, 1 part coco coir and 1 part aeration (like pumice or perlite) and amended that with some rock dust that will be literally twice as good as anything you buy in the store. The plant could live on the soil alone for ages so just a little bit of organic or organic based fertilizer here and there (like powerfeed or thrive maybe) and that's your whole cycle done easy. So anyway back to what you go going, I recommend using Powerfeed for fertilizer and Eco-Seaweed or Seasol for soil conditioner (all available at bunnings)
edit: ok ..I kinda screwed up using Miracle Grow . I was under the impression that the plants need alot of N in flowering :s , so I had been giving them this %17 stuff. They look fine just quite slow with bud development , so if I went with a lower seaweed feed ( 5-5-5 ect ) they'll get a move on with the bud size?
Plants still need N in all stage of the grow, but not as much after the first 2 or 3 weeks of flowering (as in it lowers after the stretching is through). Having too much N does not reduce bud size. If you have too much, you will be burning the leaves or sending them very dark green- and that damage is what makes it 'too much'.
Changing to another fertilizer with 5-5-5 is still the wrong ratio. Off the top of my head I think you will need something more like 5-2-6 or so. I just made that number up, but what you look for is a good N number, a low but existent P number and a K which is comparable to the N, but since it's in flower maybe just a bit higher. During the grow the ratio (again made up off the top of my head) would look something like 6-1-4.
Also you say it's 'seaweed feed', but if it's seaweed alone it will have practically no N or P and will only register as K (and a heap of trace elements). Some brands combine seaweed with fertilizer as an all-in-one kind of product. If you buy the fert and the seaweed seperate, you will be able to put the seaweed in more often (you can do it every water for example where as fert every water will burn).