I suspect the same, I am pretty sure you could have a plant fill a 10' x 10' bed if all the conditions were just right. It is definitely possible to get plants two stories tall, I've got a buddy that had a few that were almost 18' this year. His sunlight isn't the best though, so the yield wasn't as much as you would think for how big they were, and part of the reason they go so tall is that they were reaching for sunlight. Still was pretty amazing to see the tops of his plant over the roof of his house when you pulled up though LoL.
My garden is about as close as you can get from dawn till dusk, so yes I do have very optimal exposure. Which reminds me of a very important, if not the most important point to getting big plants outside:
Solar exposure and location! The location and orientation of your garden is the single most important factor to consider in my opinion. The more sun you get, the bigger your plants will get, the more they will yield, and the fatter and more resinous your buds will be.
Factors to consider when selecting a site:
Aspect and Slope. You want you garden on a southern aspect, ideally with a slight slope. A slight southern slope will not only help with drainage as Smallzz pointed out, but will actually increase your solar exposure. This is especially important the farther north you go. For example, a garden with a 5 degree slope to the south at 43 latitude, will actually have the same solar exposure as level land 300 miles further south. A southwest slope is preferable to a southeastern slope as it will take less direct solar radiation to evaporate dew or frost in the morning.
Air Drainage and Elevation. Plants need fresh air, even outside! A low area with no air movement will create all sorts of problems like increased mold and mildew, and will stay colder at night. Cold air is heavier than warm air, and will flow downslope, collecting in hollows and valleys. A garden that is on a hillside or near the top of a slope is better protected from frosts and cold air and will warm up quicker in the morning, and in the spring and fall when the weather is cooler. Cold air drainage can result in a longer growing season by as much as a few weeks at both the beginning and end of the season. This is one of the reasons you do not want your garden on a valley floor - the hills are definitely better for growing cannabis! Also, higher elevation will increase your solar exposure, just like aspect and slope does. Ideally you want your garden a few hundred feet off the valley floor, and if possible, above the fog line.
Wind Protection: Excessive wind cause physical damage to the plants, slowing their growth. It also will contribute to soil erosion. Use windbreaks as needed, and don't put your garden in a windy location if you can help it. A general rule of thumb is that a windbreak will improve growing conditions for a distance of up to 20 times the height of the break. So a 6' fence/windbreak will improve growing conditions of up to 120' from the windbreak itself. This is the main reason you will notice in pics I post of my garden, there is always a 6' tall fence around the edge with reed screening. It's not to block the view - it's to block the wind. Don't overdo the windbreaks and shade out your garden though - trading less wind for less sun is usually not a good idea.
Sunshine. Every effort should be made to take full advantage of you sunlight. If you have a tree shading your garden, cut it down and plant two more elsewhere. Even a passing shadow for a few hours will reduce your size and yield considerably.
Water. Make sure it is of good quality (get an ag water test!) and there is plenty of it. Don't rely on seasonal springs of streams, they are too unreliable. Ideally you want year-round spring or stream, or a pond. Wells can also work well, but the require a pump, and can have pH and excessive mineral issues. A gravity feed system for irrigation is always preferable - no pumps or moving parts to break or maintain. Gravity does all the work for you, and gravity never fails.
Security. Your garden should never, ever be visible from public roads. The more out of view it is, the better. The more people that see your garden, the more likely you will be busted or ripped off. This can sometimes be hard to balance with the other aspects to consider, since having a garden in a shady hollow will obviously be more out of view. Use your judgement on this one.
If you aren't using
smart pots or beds, then the native soil is something to consider. However I can speak from experience that growing in ground or in native soil is not ideal, so this is not something I consider anymore when selecting a site since I know the soil will be imported.
