A Guide to Pinching and Pruning: Increasing Plant biomass and How to Promote Branching.IntroductionOne of the questions I get asked most frequently, is how I can produce so many cuttings from so few plants. My answer is always the same: The process of Pinching or "Selective Pruning." This guide will teach you everything you need to know to get the most growth out of your S. Divinorum plants, or just about ANY other vascular plant you can grow! This works for anything where more branches are required, and if done correctly, can increase total leaf output as well.
Additionally, we'll discuss the process of "Pruning" and the differences between pinching and pruning.
A Bit About Vascular Plant Physiology [Optional]The forest shrub layer, unknown to most observers, is the most competitive growing section of any forest ecosystem. Plants in this layer not only have to compete with each other for sunlight, but have to deal with large canopy, sub-canopy and tertiary canopy layers. The end result for the members of the Shrub zone means very little sunlight and few nutrients. Plants have dealt with these harsh conditions by being naturally selected for height. It makes sense that plants able to vertically outgrow their competitors will receive the most sunlight, facilitating the most photosynthesis, and become the strongest. The tendency of a plant to produce height, called
Apical Dominance, is controlled by a set of hormones, produced to control the shape and style of plant growth. These regulators are collectively termed "Auxins"
Auxins come in many forms, and include 4-chloro-indoleacetic acid (CIA), phenylacetic acid (PAA) and indole-3-butyric acid (IBA). You might already have encountered some of these chemicals (or, at least, their synthetic brethren) in the commercially available plant root stimuators, as growth regulators are often employed to increase the formation of root buds.
Relating Auxin to Apical Dominance and how to correct thisSo, we've established the reason behind a plant's natural tendency to grow upwards, and inhibit lateral growth, and we've discussed the chemicals that make up the Auxin group... How does this all fall together? Well, it's quite simple. Without getting too far into plant physiology, we'll just summarize this into one sentence:
When the apical meristem (the topmost bud on a plant's main stem) is in-tact, the plant will show preference for Apical Dominance With this in hand, it would seem that removing this particular part would be the key to establishing more lateral growth. Well, this is actually only partially true, but is the majority of the explanation. There are a few more steps to promoting branch growth, and we'll look at these next!
How to Effectively Prune your Plants for Maximum Branch Growth (Pinching)Step 1. First off, you'll need to locate the stem that you're trying to pinch (duh!). You should have something similar to this:
You can clearly see the topmost leaf in this picture. This is the
Apical Meristem, or the
ProtoleafStep 2. Using a clean, sharp paring knife (Clean it in rubbing alcohol first before use), or your washed hands (Important!) remove this leaf. The following picture shows you a good closeup of the leaf to be removed, and where to make the cut:
Step 3. The removed protoleaf can then be placed in distilled water (It SOMETIMES roots, one out of every ten will).
Step 4. Within days (usually 4-5) two tiny little pokey buds will appear around the (now blackened) apical meristem. You can barely see them in this picture, which was taken the day after a pinching event:
Step 5. Within 1-2 weeks, the small buds should progress into separate branches, with two large lateral leaves at this branching node. You can see this development here:
Step 3. But note! You're not quite done yet! There's still more work required to truly accelerate the growth of these new branches. Those lateral leaves need to be removed. The red marks indicate where one would cut to remove the lateral leaves. Remember, don't cut these until the new branches are at least as big as those pictured below.
Step 4. Removing the lateral leaves should be done with a sterilized straight-edge... Razors or paring knives work wonders. Don't use your fingers, or "Snap" the leaf off for this one. Doing so runs the risk of removing one of your newly formed branches!
So, there you have it. A step by step guide on how to effectively pinch your plants to promote the growth of more stems. But what now? Well, after your main stems have grown to at least THREE nodes in length (three sets of leaves on each new branch) feel free to pinch them yet again! This will, again, create two more branches... You can see how pinching can exponentially increase the amount of leaves, and plant surface area available for photosynthesis.
PruningWe've discussed pinching... But what about pruning? Pruning is the process of removing the ENTIRE meristem of each plant stalk. Pinching removed only the very tip of this stem, promoting branching. Pruning, on the other hand, removes a good inch to 1.5 inches of plant material at the tip of the stalk. This promotes furious outward growth, as the plant can no longer grow taller.
Yes, you read that right. Pruning will (normally) prevent your plant from growing any taller. It will force your plant to put all it's efforts into growing sideways, by producing an extra branch (or leaf bud) at each side of every node. You'll get large leaves, protoleaves, branches and buds at every node on the plant. This is great for increasing the leaf output of your plant, but should be used as a "last ditch" resort to get your plants to grow outwards.
To effectively prune your Salvia, you must remove not only the newest growth at the top, but the developed node directly under the growth tip as well. This usually means severing anywhere between 1 and 2" of stem, and 4 leaves.
If your plant is large enough, you can can cut even lower (6 leaves, 3 nodes), remove the bottom most leaves, and make a cutting.
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