A definitive question -- and when it comes to growing respectable yields of high potency buds, it's a an important consideration.
Growers usually need to gain some experience to get the hang of planting density, which can be one of the biggest stumbling points in achieving good yields of solid and sticky nugs grown indoors.
While some marijuana strains are genetically predetermined to yield more than others, growing cannabis under lights has a lot of practical considerations that need to be addressed to maximize returns for the time spent growing and paying for necessary inputs like electricity.
If power and grow lights were free, it wouldn't matter, however, being as expensive as both of those requirements are, the goal is often to harvest as much as you can per watt consumed and paid for.
Planting density and sizing once a strain has been selected is key. Marijuana growers need to have the right number of flowering sites in a given area receiving strong and direct light from artificial light sources to realize good harvest weights. With a lot of space between buds and plants, some nice stuff can be harvested, but at a greater expense.
Conversely, you can stuff a lot of plants under the light source and while you may get a decent harvest weight, it can be mostly leafy little nugs that lack density and other qualities found in larger, better developed buds.
Again, the trick is getting the right planting density-which of course depends a lot on the strain you grow, ie does it gain a lot of height and create new flowering sites when switched into the bud phase, or does the strain stop growing and go right into producing buds, staying near the same size as when you triggered budding? This will in part determine how BIG to grow first, as well as plant spacing when finally flipped into budding.
There is a range in the amount of “stretch” that different strains tend to exhibit at the onset of flowering (usually lasting first two weeks after changing to 12/12 light cycle). Management techniques and factors such as fertility can also have an impact.
Some cultivators are limited by the number of plants allowed, so they tend to grow them big. In some instances, VERY BIG (pound plus plants). This is a slightly different discussion, although the same rule applies: the plant needs to get to “X” size and stature before budding begins to potentiate the target yield.
Whether you grow big trees or little bushes there are some universal factors. One of them being container size or the amount of space available for the root system.
While it IS possible to grow a big heavy yielding plant in a small container, typically container size and spacing is going to have a very strong determining factor on how big your plants will finish, especially when grown in soil.
Strains may have different rates of growth, but typically the goal is to have six strong main branches per lineal square foot under the grow lighting source. On average, a 1000w HID (high intensity discharge) grow lamp provides strong light in a four foot by four foot area when operated with a good reflector suspend at an optimal distance above the plant canopy.
For a lot of Indica dominant strains, including Cup-Winning Kush strains, these guidelines work well as a rule of thumb under grow lights, per 4' X 4' area with intense lighting:
25-36 one gallon pots, 5-7 days vegetative growth
9-16 two gallons pots, 10-14 days vegetative growth
6-9 three to five gallon pots, 14-28 days vegetative growth
4 ten gallon pots, 21 to 42 days vegetative growth
1-2 twenty gallon pots, 28 to 56 days vegetative growth
Other determining factors include management practices like pruning, bending and staking (and of course, strain selection). However, getting planting density right and making sure plant growth doesn’t become restricted due to issues like crowded root systems while leaving space that is `just right` up top to produce good quality buds (and enough of them) keeps crops on track to good yields for cultivating efforts.