Does Removing Leaves Make Sense for a Better Harvest?
The topic of leaf removal, defoliation, or, in technical terms, defoliation has been the subject of passionate debate among growers for many years. Among growers around the world, we can find both staunch opponents and supporters. There is therefore no generally accepted verdict on whether it is better to leave plant leaves alone or whether it is worth devoting attention to this technique. The fact remains, however, that professional growers also repeatedly use it on various plant species and achieve impressive results, so this technique probably does have something to it. All the more so because today, even in home conditions, an increasing number of experienced indoor growers consider defoliation a normal part of their cultivation routine, which significantly contributes to their high and regular yields.
We also know the natural process of defoliation from nature. Just think of leaves falling. Let us now explain why the targeted removal of plant leaves makes sense not only in outdoor growing, but also in the case of indoor cultivation of plants under artificial lighting such as usually LED lamps or discharge lamps.
Improving air circulation and reducing humidity inside the growing space
In indoor growing rooms and inside grow tents, practically any vegetation is often very dense to impenetrable, because every grower naturally tries to use the growing space with artificial lighting to the maximum in order to grow as many healthy plants as possible in the given area. The number of plants does not have to be the only priority. Some growers let the plants grow considerably before changing the photoperiod so that they fill the entire growing area as much as possible.
However, far from all of these growers realise in practice that the denser the vegetation inside the growing space, the more it ultimately hinders the flow of fresh air between individual plants, which is very important for their healthy and vigorous development.
Our TIP: Circulation fans help increase the flow of fresh air around plants precisely where it is most needed. If you do not yet have one in your grow box or room, even at the start of summer, be sure to read the separate article: How do you choose a circulation fan?
Another problem arising from the fact that plants carrying lots of leaves are crowded together inside the growing space is increased humidity. Humidity itself is not such a big problem, but in combination with the above-mentioned lack of fresh air supply, exhaled air from the plants accumulates around their lower leaves. This air is no longer sufficiently saturated with carbon dioxide (CO2). The significance of CO2 for plants is also covered in a separate article: Plant growing and carbon dioxide. How and why should it be used?
Our TIP: Give plants in the grow box an extra dose of carbon dioxide thanks to the natural CO2 generator!
If we have dense vegetation in the growing space, insufficient fresh air circulation around individual plants together with increased humidity creates an ideal environment for dangerous moulds, which thrive in such stagnant air. Where plant leaves touch, the highest concentration of moisture also occurs, and therefore the leaves are often wet and stuck together at the points of contact. And that is exactly the phenomenon you want to prevent.
Improving light access to plants
For plants to develop, their green parts, by which we mean primarily the leaf area, must receive enough light radiation. Moreover, it must be of sufficient intensity for most leaves to receive their daily portion of photons. In nature, this is arranged by the sun, which is not only a source of light with extremely high radiation intensity, but also moves across the sky during the day, gradually changing the direction and angle at which the sun’s rays fall on plant leaves. In indoor gardening, even the most powerful light source remains fixed in one position all the time. The above-mentioned density of vegetation therefore also becomes an important variable. It is common for less light to penetrate into the lower levels, so that leaves in the darker parts of the growing space do not achieve the optimal level of photosynthesis. Therefore, if we set aside the effect of defoliation for a moment, TLED lamps for supplementary lighting of shady areas are used in grow tents or other indoor growing spaces.TLED lamps for supplementary lighting of shady spots.
Our TIP: 100W full-spectrum supplementary luminaire Lumatek BAR 2.9
It probably will not surprise you that a plant does not decide that it will stop supplying these insufficiently lit leaves in the lower levels with water and nutrients, because the grower usually cares mainly about the flowers or fruits. And that is precisely why these leaves become a non-negligible burden for the plant. This is where we get to the heart of the matter.
Experience with defoliation - leaf removal - speaks quite clearly. It is enough to let more light reach the flowers by removing unwanted leaves in order to notice a visible improvement in their development. On the other hand, leaves can be compared to solar panels as a reservoir of energy used by the plant, which is needed, among other things, for the formation and ripening of flowers. Therefore, defoliation must be approached very sensibly if it is to be beneficial and not harmful... Let us therefore explain the four basic rules that you should definitely respect before you put this gardening method into practice.
- Plant health
Whether it is mainly thanks to your growing experience and skills, or thanks to premium products from our range, which we mention in more than one other article here on the blog, your plants must be in perfect condition. Otherwise, do not start targeted leaf removal at all. There is no point in doing so. If your plants are dealing with pests, or if it is clear that their growth is not yet optimal, defoliation will bring no benefit and will more likely harm your crop. Healthy plants naturally have everything to do with optimal growing conditions in indoor plant cultivation. Therefore, before you begin leaf removal, first make sure that your plants have enough light and the ideal climate (see above), and that you are able to provide them with the correct dosage of important nutrients as part of regular watering. If everything is in order, you can begin to experiment.
- Genetics
Opinions on defoliation in the international growing community differ considerably, possibly also because not every variety is suited to leaf removal. Genetics certainly plays a role here. If it is a variety that forms dense vegetation with a large number of side branches and leaves, it is likely that defoliation will indeed benefit it. However, there are also many varieties of different plants with a more open plant structure, for which it is natural to produce only a smaller number of leaves. Here we already lean towards caution and minimalism. This means that, provided rule number one is met, you can first try defoliation on a very small scale and observe how your plants react compared with places where no leaves were removed. If the effect is positive, you can carefully continue with the targeted leaf removal process. And then there are exceptions, which makes the situation a little more complicated. Morphology is not everything, and therefore some varieties may ultimately respond better to leaf removal than others, regardless of their structure or total number of leaves.
- When less is more...
Some growers do not make a fuss about it and remove almost all large leaves in one go, leaving only smaller leaflets near the flowers and leaflets attached to the stem that do not yet have a fully developed petiole. Only a grower who knows exactly what they are doing, namely which variety they are growing and how that variety reacts based on repeated experience, would dare to do something like that. Or, on the contrary, someone who knows absolutely nothing about defoliation, but that is pure gambling. So if you decide to try leaf removal in practice, we recommend following the well-known rule “less is sometimes more” and starting defoliation very cautiously. First remove only a few large mature leaves. Then wait several days and observe how the plants react. Based on that, you can more easily consider further defoliation.
- Correct timing
Think about the point at which the proverbial back door is closing. During the vegetative phase, plants are still growing new leaves, usually before the photoperiod changes to 12/12. At this time, plants devote all their energy only to the formation of stems and leaves. Plants then continue to produce new leaves for approximately three more weeks after the photoperiod changes to the so-called flowering mode, while they rapidly grow taller. Once they stop growing taller, no new leaves will grow either, apart from the fine leaflets in the immediate vicinity of the flowers.
Further useful tips for leaf removal can be summarised in the following points:
- Removing leaves from seedlings or young plants in the early stages of development makes no sense. They need to devote as much energy as possible to development, and they are also usually spaced sufficiently apart. As a result, light of sufficient intensity falls on all levels of the young plant, which supports the growth of side shoots.
- For precise, safe, but also more comfortable and faster leaf removal, you will find quality, modern garden scissors useful.
- Growers in practice often also deal with the dilemma of whether to pinch off leaves with the petiole or leave the petiole in place. Leaving the petiole will do no harm, because the petiole does not block the penetration of light and, after it has provided the plant with its contained nutrients, it naturally dries out and then falls off on its own.
- Sometimes it is not necessary to remove whole leaves and it is enough to cut off only part of the leaf blade. This method of defoliation can be advantageous if there are not many leaves, but at the same time they take up a lot of space because of their size and prevent light from passing through.
So now you know the basic rules for leaf removal, and we can now focus on specific recommended procedures for defoliation of plants grown in an indoor environment.
- In the growth phase (or during the growth photoperiod in indoor plant growing), we have several options for using leaf removal:
- If you need to achieve an even height of the green growth, removing leaves from selected branches, which will slow growth as a result of defoliation, will help you.
- When you remove large leaves that tend to shade, more light reaches the shoots and branches even in the lower levels. This supports their development and at the same time leads to more efficient use of the total growing space available to you.
- We now return again to the phenomenon described above. You should definitely remove leaves that touch each other and where moisture condenses on their surface at the point of contact, which favours mould or powdery mildew. If, at this stage, you notice old leaves in the lower part of the stem that no longer receive enough light, remove them as well straight away.
- Once you change the photoperiod to initiate flowering, the plants will undergo intense upward growth for the next approximately 3 weeks, and flowers will also form. There is an established English term for this phase: “stretch”. You may also have come across plants that flower regardless of photoperiod. We refer to these varieties as autoflowering. They usually also require special nutrition, such as BioNova Autoflower Supermix. With autoflowering plants, the individual phases of the cycle simply have to be determined by eye - according to how they look and whether they are already visibly forming flowers. In any case, remember that the aim of defoliation in the flowering phase is to get as much light as possible to the flowers, while at the same time trying to leave the plant with a sufficient number of leaves. Yes, it is a certain art of balancing on the edge, but the more experience you have with leaf removal, the easier it will be for you to achieve the desired balance in the process of defoliation.
Our TIP: A new range of premium hand tools that will last you for years will make defoliation easier once and for all. Stainless steel blades, such as those on the small PRO CUT garden scissors with eye, stay sharp for longer.
When and how should you defoliate? The strategy is in your hands
- Before changing the photoperiod
An increasing number of growers practise radical leaf removal just before changing the photoperiod. After the photoperiod changes, the so-called stretch phase begins (see above), which doubles the final effect of defoliation. To a certain extent, this should help you limit the stretching of branches upwards, but the main significance lies in the greater amount of light falling on the lower internodes. A sufficient supply of intense light in these places will then significantly support flower development, which would not do so well in the shade of leaves.
- Ongoing defoliation
We will now present a much more conservative approach to leaf removal. It consists of the ongoing removal of leaves during the growing cycle, right up to the final flowering stage. You can set certain intervals for regular leaf removal, say every other day, for example. However, it is similar to watering - better more often, but in smaller amounts. Therefore, always remove only a few selected leaves that are shading the flowers the most at that moment. Or leaves that are touching each other. This conservative approach helps prevent unexpected shocks that plants may experience after the one-off removal of a larger number of leaves. At the same time, you have room to test how the given variety reacts to leaf removal without causing more harm than good.
- Comparative test
The real potential, or rather the possible benefit, of defoliation for the development of the variety you are currently growing in a controlled environment can be revealed by a classic comparative test. It is up to you how large an area of vegetation you compare. Let us say you split it fifty-fifty. That means you subject one half of the growing area to defoliation and let the other half grow freely. However, the comparative method also works for comparing different approaches to defoliation. So we again return to the fact that the best thing is to observe the plants carefully, and the differences between the two halves or other proportions of the growing area you choose will help you clearly determine which path to take in order to achieve a plentiful harvest. Do not forget that the basic condition for this comparison is that all the plants being compared are the same variety and that all the plants being compared have the same conditions for development available in the growing space.
If you have any questions, do not hesitate to contact us via the well-known e-mail address info@higarden.eu.
We also recommend these products:
- PRO CUT garden scissors - large straight
- PRO CUT garden scissors - large curved
- Easy Snip curved scissors
What to read next: