- Weedguru Higher
- Posts: 14620
- Joined: Sun Mar 30, 2003 1:31 pm
- Location: Canada
Topping the plant means that you remove the main shoot located on the central stem. By doing so you will encourage the plant to grow into a bush with a lot of shoots, instead of one big main shoot that you get on the untopped “Christmas tree”.
The reason why the plant behaves this way is because the centre of growth control is located in the apical meristem or main shoot. The main shoot sends suppressive hormones down to the lower branches which stops them from growing. This is called apical dominance, a mechanism that favors the energy efficient, triangular shape of plants in the wild. By removing the main shoot, the lower branches become free to grow at full rate in order to take its place.
Topping a Plant
1. Locate the very top of your plant and cut through the main stem just below the newest growth. This should be done after the 3rd or 4th leaf set but can be done at any time after the 3rd leaf set.
2. Shows Plant Top cut off and where the 2 new Branches that will form a "Y" in the main stem will grow from.
3. Shows the newly topped plant after 2 days of growth, notice the Y in the Stem Forming.
The main shoot also has other functions. It communicates with photosensitive pigments, called phytochromes, located in the leafs.
Flowering in plants is triggered by two things. The first part of the system is called the Circadian rhythm which is basically an internal biological clock. This biological clock is an evolutionary response to light and darkness and is tightly linked with hormonal functions in the plant. The second part involves hormone signalling mechanisms, messenger molecules and specifically encoded proteins that tell the plant to start budding based on the information that it receives from the environment. The plant knows when to trigger flowering because the sensory pigments keep track of the photoperiod or the hours of daylight and relay this information to the centre of growth control which is located in the main shoot. The sensory pigments also inform the plant of how much sunlight a certain part of the plant receives, which enables it to relocate energy and growth hormones to where they are needed.
There are several types of hormones that regulate growth. One of the most important growth hormones is called auxin. It originates in the main shoot and is part of a mechanism called the auxin transport system. This hormone plays a big part in the internal signaling and growth control mechanisms of the plant. It also regulates the formation and behavior of other growth hormones that are responsible for everything from root growth to the formation of flowers.
By removing the main shoot, the communication between the leafs and the main shoot ends, effectively canceling the apical dominance. The result is that the plant assigns the next shoots in line to the job. This means that the smaller shoots on the branches beneath the cut starts growing faster and gain height. Since there is no more apical dominance, the plant will grow into a bush because the newly appointed main shoots all have equal priority. These shoots usually grow very slowly when the plant is left untopped. It is probably best to top the plant at night when most of the hormones have been sent to the roots, which means that there is a smaller chance of the plant being stunted after the main shoot has been removed.
There will be a short period of time when the plant is in something that could be called a state of confusion. It will stop all activity until it can figure out what is going on, so to speak. It will resume vegetative growth as soon as the hormonal functions are up and running again. It should take no more than a few days for this to happen, a week at the most.
Most of the time this transition is quite fast but some plants that respond poorly to topping might have stunted growth for a while. It is possible to top a plant many times, each time the number of main shoots will double. Give your plants some time to grow before you top them, if they are topped too early they might get stunted for a while. I do top them quite early sometimes as you can probably tell from the pictures that I have included. Go by your feeling, once the plants look strong enough you can start topping and training them.
This is a good way of training the plant if one wants to make the most out of the space available. Topping is also a good way of slowing down plants that tend to stretch a lot, as each time the plant is topped it will redirect energy to a greater number of shoots. The new shoots will never grow as large as the untopped main shoot will but they will most likely produce a larger crop.
Personally, I have used the topping technique in every single one of my grows. It's the easiest and quickest way to maximize your harvest (comment by Weedguru Higher)
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