Every genetic, every plant has an optimum size range when grown indoors.
It is important to differentiate between optimizing for your yields in your space and optimizing for a plant’s optimal size, at which it will naturally grow to the best of its ability.
A plant’s optimal size is the size that a plant will reach naturally that allows it to maximize overall quality and characteristics, demonstrating ideal terpene and cannabinoid profiles, structure, lateral branching, internode spacing, and flower size, as well as an immune system that is healthy enough to resist outside threats.
Maximizing bud depth and a genetic’s vigor during flower will be major deciding factors in determining a plant's optimal zones. An untopped plant, grown according to its natural morphogenesis and grown indoors, will typically produce 3-8 ounces at its preferred size. Some plants like to be grown big, but even commercially-grown varieties that love to grow big won’t have an optimal size that yields much more than eight ounces. For some plants typically indicas with smaller flower sets, a 2-week veg that yields 30 grams is the most effective way to grow that plant.
Size vs. Space
As touched on, there are many different ways to grow, all of which are dictated by the goals, or endgame, of the grower. There is a difference in approach to getting the maximum yields out of an area and growing a plant to its optimal efficiency. The method that attempts to best find the intersection between these two goals is “Sea of Green;” at scale, sea of green is the most efficient technique for keeping plants close to their optimal size while producing the most yield within a particular space.
Sea of Green:
The idea behind sea of green is that, once your canopy has filled out, all you see when you look over your crops is a “sea of green” made up of all of the plants’ leaves that form a complete canopy that fills the space using single cola plants that have not been topped. These plants are kept smaller, and are typically flowered from clone after 1-4 weeks of veg. To produce the highest efficacy indoors, measured in both flower and oil production in a space, the Sea of Green method is the best option.
The highest yields that I have ever seen were off of a 98-plant grow under 800W of light (2-440W HPS). Each plant was kept to under an ounce, but we still yielded 3430 grams total, 3.8 pounds per 440W light. That means each plant’s size would yield about 25g of buds, multiplied by 98 plants, all grown in a 10x5’ space in 4” rock wool cubes. Not only were we getting 4 pounds per 440W light, but we were doing it with a 1-week veg; the time from clone to harvest was drastically reduced. It is important to obtain metrics whenever possible when attempting to maximize your space. To this day, this showed us the maximum amount of flower that I could get in a space over a specific period of time.
If you are using a trellis to spread your plant(s) out, then a plant’s optimal size is less relevant and its vigor and morphology are more relevant. With a trellis, the approach is to fill the space as best as possible with the plants that you have, stretching the branches and leaves out to produce new growth sites. Similarly, if you are growing in a greenhouse or growing for outdoors, approaching a plant’s optimal size vary as the conditions are much different.
To get maximum yields from indoor setups, the optimal approach is to have more small plants, typically plants in the 10-60g (dry bud weight) range. If you’re flowering vertically (as opposed to a trellis), with a fixed space for the roots (as opposed to outdoor), the smaller the better when flowering a sativa, as many genetics will still grow to over five feet in height.
Optimum Plant Size:
The most common range for a typical commercial plant is in the 80-150g range. Plants with sativa leaning expressions are going to be closer to 200g or more because of the amount of extension and growth in the first half of flower that they are known for.
Two different examples of plants with these traits are NL5 x Haze and Jack Herer. Both of these plants need nominal veg time, and the NL5 typically none. Even with this abbreviated veg cycle, these plants will usually yield upwards of eight ounces because, untopped, these plants can easily grow to be six feet tall. The first three weeks of flower, sativa-leaning expressions have extreme growth and vigor, and the flower sets won’t even begin stacking until Week 4-6.
You’re going to get as larger or larger flowers as you will with a plant veg’d any amount longer, and you may even see a diminishing return if you overveg a sativa expression plant. The absolute max veg time for a true Sativa is no more than four weeks, and really 2-3 weeks if growing from clone. Throw that clone right into its final pot and flip it shortly thereafter, especially with hyper vigorous hazes and haze crosses that reach their true ripeness in about 80 days. These plants have a bare minimum of 10 weeks of flowering time.
Unlike faster flowering varieties that need a slower flip to get that extra growth (an 8-week strain may stop vertical growth by middle of Week 4), a 70-80 day strain will continue vertical growth at least through week 5 before it starts stacking hard, and that’s largely a result of the fact that sativa root vigor is sometimes 2-4x that of a typical plant. Photo plant root tips typically slow down in correlation with the rate of a plant's vertical growth; Week 3 will have the most aggressive vertical growth, and in Week 4, that growth begins to slow down, as does the root growth of the plant. Root tips have typically stalled growth by the end of Week 5/Day 35. When the flowers begin to swell, that is your indicator that your root tips are no longer active.
In a commercial grow, you have to have some sort of reasonable height, reasonable growth, and controllable conditions. If you aren’t going to trellis plants out, I always err on the "smaller the better" as far as size of the plant going into flower if it has true sativa expressions or you are even possibly worried about overgrowing your space.
SEEDS & CLONES
Optimum Size for Seed:
Seeds are not able to flower until they are at least 4-6 weeks old. Female plants need to produce ethylene in order to flower, and seeds don’t produce ethylene until typically Week 5-6 of veg. Because you have to grow a seed for a minimum of 5-6 weeks before flowering, it can limit the versatility and narrow the scope of what I believe to be optimum for a plant. An exception to this rule are Afghan Kush-dominant varieties that are able to flower more quickly from seed; It can finish in under three months from germination. Autoflowers adhere to a different set of parameters.
Optimum Size for Clone:
Conversely, clones offer more versatility with shorter veg cycles than when growing from seed, because a clone can be flowered as soon as it is rooted. Clones can be sent into flower and are able to flower at your discretion, allowing you to shorten or lengthen veg time based on the variety and expression in question.
One rule that I have for my seeds is that I typically recommend flipping the plant once its fan leaves have outgrown the diameter of its final pot. Seeds will often take a week longer to flower than when flowered from clone because of the maturity (hormones) of the plant, especially when flowered young (less than 10 weeks).
High Yields vs Best Material
You will get the best material from the most efficient plants, as there is a point of diminishing return in quality when working with larger plants. You will also notice that your bud and plant structure is more consistent at the plant’s optimal size because flowers aren’t sprouting up outside of your optimum canopy range, resulting in less “larfy”, immature buds which steal nutrients and energy from the plant. Always remove any undesired growth, whether it be internodes, leaves or poorly developed flowers.
Determining your endgame for your garden and your space will guide your efforts to find a balance between optimum plant size and maximum yields for your grow. If your goal is to harvest the best flowers in the most efficient manner, then a larger amount of small-medium plants grown in a Sea of Green method will give you the results you’re looking for.