▷ Avocado trimming from A to Z!

And here I am writing again about a plant very dear to #clangeorgici (and how could it not be!): our beloved Avocado. This fruiting species seems to have no more secrets for us, we have seen how to make its seeds germinate with an easy experiment and we have investigated the phenomenon of albinism. A bit like the post-war period gave us the baby boomers, the #avocadochallenge has also often left us true Home Avocado groves. We look after them and take care of them with infinite dedication and, let’s face it, they know how to repay us with satisfaction.

Among the cultivation practices that could be useful in managing this plant there is undoubtedly the intervention of height. Now I’ll tell you about it in detail, before leaving I would just like to point out that this practice does not only concern avocado but is widely used in floriculture and horticulture: by trimming the Avocado we will try to learn the mechanism underlying this procedure, as we did for the germination of the seed, aware that these principles are valid for all plants.

In the next lines we will therefore define these aspects:

What is meant by ‘topping’
Is trimming an essential intervention?
At what stage of development can I prune Avocado
What time of year can I trim avocado
How to properly trim Avocado
Notes on plant physiology relating to topping (only for braves)

What is meant by the term shearing

This agronomic practice is fully included among the pruning interventionsalbeit light. It involves the removal of the apical buds and can affect a single stem (normally the main one) or multiple stems (in the case of shrubs or in the case of pruning also carried out on secondary branches of the plant).

The objective of trimming is to favor the tillering of the plantthat is, the promotion of new secondary branches, providing the specimen with more structured, thick and luxuriant foliage. Cutting off the apical bud stimulates the emission of new jets from the latent lateral buds. Technically it talks about ‘removal of apical dominance’, we talk about it at the end of the article for plant nerds who are interested in a scientific in-depth analysis.

Is trimming an essential intervention?

Absolutely not. Whether or not you decide to trim the Avocado (or any other plant) its vitality will not be affected in any way. So why should I go through this painful moment? Normally this is done for limit growth in height of the plant and/or to favor its tillering, as mentioned above. Incidentally: I said that it is a ‘painful moment’ meaning that it is always a little scary to cut off the stem of the plant, depriving it of its beautiful foliage and finding ourselves with a wooden stick; However, I would like to point out that for the plant it is not a traumatic interventionindeed, it often benefits greatly from trimming.

You will certainly have noticed that not all avocado plants develop in exactly the same way: some are thicker, others less; some grow very tall, others remain more compact. Especially when you find yourself in low light conditions (perhaps because the plant germinated in winter, when the available light radiation is limited) it may happen that the plants tend to ‘row’, that is, to grow very tall, greatly lengthening the internodes (the portions of the stem between two nodes). If the concepts of ‘node’ and ‘internode’ are not clear to you, you can find the explanation in the video that accompanies this article. Other causes regarding the heterogeneity of the specimens can then be traced back to normal genetic variability of plants born from seed, also considering that we often germinate Avocados belonging to different varieties.

The lengthening of the internodes is the solution that the plant instinctively adopts to stand out as much as possible and reach greater heights in order to intercept more light: think of coniferous forests where you can see those very tall plants that run straight in competition with each other to earn the light. Which is fantastic if we want to grow fir trees to produce wooden planks, less so if the intention is to make ourselves look good to the guests by showing off a textbook domestic avocado. I’m talking about those plants that are often more similar to amateur radio antennas than to an Avocado, a little thin and haggard, not very aesthetic. Here, pruning can be a solution to compacting the foliage and getting the plant back into shape.

In general: if you want to slightly compact the size of your Avocado that you are growing in soil, water or semi-hydroponics you need to provide a good amount of light. If it has now ‘escaped’ you can think about trimming it.

At what stage of development can I prune avocado

The stage of growth within which the trimming intervention falls is also discretionary, that is to say we don’t have a precise rule to follow. Personally, I prefer to wait until I have at least 4 or 5 nodes on the avocado plant (which usually means 4 or 5 leaves).

What time of year can I trim avocados?

If possible I recommend one season of strong vegetative growththerefore I would intervene from late spring until the entire summer and early autumn. I believe that i ideal months are May and June. However, I have also experimented with topping Avocado in winter, obtaining the desired effect, albeit with longer times and a more consistent effort on the part of the plant.

How to properly trim avocados

Let’s move on to the operational phase! Try to have a sturdy pair of scissors or gardening scissors available and sterilize the blade using a flame or alcohol. Avoid using alcohol and flames together if you don’t want to risk setting fire to the avocado grove and the living room.

Are you ready? Well…

Observe the stem of the plant and try to identify where the buds are: you will find them near the nodes, often denoted by an enlargement of the diameter of the stem.
Choose the gem you want to keep as a terminal: everything above it will be cut. The choice, once again, is discretionary. You can choose to cut above the first bud from the bottom (in this case, however, you will not have the emission of lateral branches in the short term) or to remove only the apical one (the last one at the top. As often happens, I suggest turning to an intermediate solution: try to understand at what height you would like to root your Avocado and find a bud near that interval.
The cut must be made 0.5/1 cm. above the gem, preferably obliquely. It must be as clear and clean as possible, without smudges.
Leave the plant in its original position and, if you have it available, administer some biostimulant at the first useful watering.
Within 2/3 weeks you will obtain the emission of one or more lateral branches.

Notes on plant physiology relating to topping (only for braves)

Let’s try to understand why cutting an apical bud should induce the tillering of a plant. The phenomenon is due to the existence of a phytohormone called Auxin, the most abundant plant hormone in plants. It controls the processes of growth and development (from the Greek “auxein“, which means to grow), in concert with other hormones: we use it every time we prepare a cutting with the rooting hormone (made up of Auxins) and we admire its effects when we see a stem leaning towards the light source.

Auxins are a class of plant hormones (or growth regulators) synthesized by the plant at the apical meristem level (the tissue at the top of the stem and which produces plant material, pushing the plant in height). The meristem is a tissue of undifferentiated cells, like animal stem cells, and generates other tissues depending on the position in which it is found: a root meristem, being underground, will produce roots; an apical meristem will produce aerial organs (leaves and stems).

Just think that Auxin was the first phytohormone to be identified and… not by the first one! Its functioning was hypothesized by Darwin himself in his book on phototropism «The power of movement in plants» in which we find references to observations on the development of some plants that inclined their growth towards the light source. Only in 1926 (i.e. after almost half a century) the Dutch biologist Frits Warmolt Went identified the Auxins and traced their action to Darwin’s observations (but how far ahead was Charles?).

One of the commands that Auxins give to the plant organism is the following: ‘do not branch laterally, continue to invest energy in the apical bud, so that the plant grows ever taller‘. The further you move away from the top of the plant, the more the effect of the Auxins decreases: this implies that the lower parts of the stem are more inclined to branch laterally.

To understand the effect of this mechanism, it is convenient to refer to fir trees and conifers in general, in which a crown shape resembling a cone is observed: large and extended lateral branches at the bottom of the crown, gradually shorter and sparser towards the top.

I could talk about Auxins for hours, just think that phenomena such as phototropism (mentioned before in Darwin’s experiment) and gravitropism (the plant’s response to the force of gravity) are linked to this phytohormone.

The antagonist of Auxin is Cytokinin (discovered in the 1950s by Folke Skoog), which is also generated by meristems butradicals‘ rather than ‘apical‘. One of the commands given by this hormone is in fact opposite to that of the Auxins and can be summarized as ‘branch laterally and do not grow in height’. Even in this case its effect is milder as we move away from the roots and rise towards the top.

Cytokinin also affects many other plant processes and I will try to reserve the right space for it in the future. For now it is enough to conclude that: when we go to trim a plant we eliminate apical dominance (i.e. the control action exerted by the apical bud through Auxin), leaving more space for the cytokinins and thus obtaining greater tillering of the plant.

As you will notice, topping does not imply stopping the plant in height. Sooner or later one of the lateral buds will be promoted to a new apical bud: its bud will bend upwards, continuing the height development of the specimen.

I have concluded, I hope I have been clear and understandable but for any doubts or omissions on my part, feel free to quiz me in the comments on the post.

Happy topping #clangeorgici, I hug you and wish you healthy and lush plants (but only if you fertilize them!).