5.2 High-Stress Training: Topping, Fimming, & Mainlining

Topping is the most common form of HST and the one most growers start with. It involves cutting off the top of the plant's main stem.

• The Method: Once your plant has developed 4-6 nodes (sets of leaves), locate the main stem and with a clean, sharp pair of scissors or a razor, cut off the top, just above a new node.

• The Result: Removing the main growth tip, known as the "apical bud," eliminates the plant's apical dominance. This is the hormonal signal that tells the plant to grow in a single, upward column. By removing it, the plant sends growth hormones to the two new stems directly below the cut, which then grow into two new main colas. Over time, this transforms the plant from a "Christmas tree" shape into a bushier plant with multiple primary stems.

Fimming is a variation of topping that gets its name from the acronym "F***, I Missed." It's a less precise cut that can produce more main colas than topping.

• The Method: Instead of cutting off the entire top of the plant, you only remove about 70-80% of the new growth tip. This is often done by pinching or snipping the very top.

• The Result: While topping typically results in two new main stems, fimming can confuse the plant enough to produce three or four new main growth sites from a single cut. The plant doesn't lose its apical dominance as completely, so the central stalk can still continue to grow, although at a reduced rate.

Mainlining is a more advanced and intensive form of HST that combines topping with LST principles to create a perfectly symmetrical plant. The goal is to create a "manifold"—a central hub from which an even number of branches, typically 8 or 16, grow.

• The Method: This is a multi-step process that requires a longer vegetative stage.
  

1. First Topping: Top the plant early, usually at the 6th or 7th node.
2. Pruning: Remove all growth and stems below the third node, leaving only a single pair of stems to form the manifold.
3. Second Topping & Training: Allow the two remaining stems to grow, then top them again to create four. Repeat this process until you have your desired number of main stems (e.g., top twice more for 8 stems).
4. Symmetry: Throughout the process, use LST techniques like tying down to keep all main stems at the same height and distance from the central manifold. This ensures even nutrient distribution and equal light exposure for every cola.

• The Result: Mainlining creates an extremely efficient plant that can produce multiple massive, uniform colas with very little "popcorn" bud, making for a streamlined and high-quality harvest.