The modification of a plant's growth habit is called training. Indoor cultivators employ many training techniques to encourage shorter plants and denser canopy growth. For example, unless the crop is too large to be extensively pruned, cultivators remove adventitious growth shoots, often called suckers that are near the bottom of the plant and/or receive little light and will produce poor quality buds. Some cultivators employ plant-training techniques to increase yields indoors:
Topping is the removal of the top of the apical meristem (dominant central stem), called the apex or terminal bud, to transfer apical dominance (the tendency for the apex to grow more rapidly than the rest of the plant) to the shoots emanating from the two nodes immediately beneath the pruning cut. This process can be repeated on one or both of the two new meristems, when they become apically dominant, with the same results. This process can actually be repeated nigh infinitely, but over-diffusion of apical dominance produces smaller, lower quality buds, so it is usually done no more than a few times. Topping also causes more rapid growth of all of the branches below the cut while the plant heals.
Pinching (also called "FIMing") is similar to topping in that it causes lower branches to grow more rapidly, but the apical meristem maintain apical dominance, which is especially useful if the plant has already been topped. Pinching is performed by firmly pinching the apical meristem(s) so as to substantially damage vascular and structural cells but without totally breaking the stem. This causes lower limbs to grow more rapidly while the pinched tissue heals, after which time the stem resumes apical dominance.
LST stands for Low Stress Training and is another form of super cropping, many times referred to as LST super-cropping. This technique involves bending and tying the plants branches to manipulate the plant into a more preferred growth shape. This method of training works very well for indoor growers who need to illuminate their plants using overhead lights. Since light intensity greatly diminishes with increased distance (Inverse-square law), LST'ing can be used to keep all growth tips (meristems) at the same distance from the light and can achieve optimal light exposure. LST can be used in conjunction with topping, since topping increases axial growth (side shoots). Topping is often done a few weeks before beginning LST'ing. The training works by changing the distribution of hormones—more specifically auxins—in the plant. LST'ing resembles the training of grape vines into their support lattices. Outdoor gardeners also employ training techniques to keep their plants from becoming too vertical.
In contrast to the "Screen of Green" method, Sea of Green (or SOG) growing depends on the high density of plants (as high as 60 per square meter or 6 per square foot) to create uniformity in the crop. In this technique, which is often grown in hydroponic media, only the colas of the plants are harvested. Containers are used to enforce the geometric distribution of flowers and plant material, as well as their exposure to lighting and atmosphere. Sea of green is popular with commercial cultivators, as it minimizes the amount of time a plant spends in vegetative stage, and allows very efficient light distribution, keeping the plants much closer to the lights than when grown to full size.
SCROG, short for SCReen Of Green, is an advanced training technique for cultivating Cannabis, mainly indoors. Closely resembles SOG (or Sea Of Green) with the difference being that SCROG uses extensive training to produce the same field of bud effect with only one plant. Medical growers may find this a helpful technique to maximize harvest if they are only allowed a certain number of plants. A screen such as chicken wire is hung over plants so that the tips of branches are kept at the same level. This allows even light distribution to all of the nodes/bud sites. Once the flowering stage begins, the flower tips reach through the wire and are at relatively equal distances from the light source.
Vegetative state: The plant should remain in the vegetative state until 70 to 80 percent of the net is full. As a branch reaches 7.5 to 10 centimeters (3-4 in) above the wire it is pulled back under the wire and so trained to grow horizontally until flowering. Because of the amount of plant required to fill the net, the vegetative period may require longer than normal to be ready for flowering.
Timing: Timing is vital to the success of a SCROG grow. If the net is not full at harvest, valuable space has been wasted. If the net is too full then the buds will be too crowded to develop properly. Knowing how a plant grows can help to visualize when to flower for maximum effect.