When you grow, sooner or later you run into trouble. As a friend says: “He who cooks and kneads, everything happens to him.” Any activity with a certain complexity involves “problems” that, over time, you realize were not really problems, but part of learning. One of the main problems that every grower has encountered once in his life is finding yellow leaves in his marijuana.

If you involve living things in these activities, we have the added difficulty that they can die, you have to hurry to find solutions before this happens and time passes quickly in a crop.

If we focus on cultivating cannabis in our hobby, we must also bear in mind that the success of our harvest depends on our other hobby, smoking cannabis. This requires us to have some very basic knowledge of botany and biology, to be able to smoke without accessing the illegal market. Today we are going to help you with a problem that usually appears sooner or later in all crops: the yellow marijuana leaves of our crops.

Chlorosis, the scientific name of this disorder, is not actually a disease, but a symptom of different deficiencies that we will see below. Our plant is not photosynthesis in any of the leaves and that must have a reason, usually that the plant cannot assimilate nutrients or that these are not available for various reasons. After determining that the number of yellow leaves in your marijuana is excessive, becoming something unwanted, you have to do a little more research to see the root of the problem. Let’s see what are the causes, how to check it and how to fix it.

In the last two or three weeks, this is very likely to happen  for several reasons: the same age of the plant makes it weaker and needs to detach from some leaf to end its life cycle, think of autumn, the plants prepare for winter, dropping their leaves, already dry, or directly die.

After a root wash

want do i do with the yellow leaves of the marijuana plant

Also if you have washed the roots to prepare the harvest or used a nutrient cleaner, or have just stopped feeding them for a few days, it is possible that it is missing some food and takes it out of the most expendable leaves. During this phase it is likely to happen due to the great effort it puts into forming its flowers. It needs as much energy as possible and sometimes throws reserves, and the leaves are a good source of energy, very fast and easily available. There are a few varieties that wipe out almost all the leaves around the all-yellow buds. Don’t worry, it’s part of the normal growing process.

Marijuana problems with yellow leaves

This can happen in many crops in the flowering phase, they can partially block the roots. You have to act quickly, because the resulting cannabis will “scratch” more in the throat when smoking and will not give you the production it should, since the plant does not have enough food available and the buds will be excessively spongy. In some cases the plant will stop growing and will barely give you production. The lack of elements causes the plant to not be able to photosynthesize some leaves due to lack of nutrients to build chlorophyll.

To check that you have an excess of salts you need a plate to collect the water to be analyzed and an EC meter.

Potting method: water the plant a little, when it has absorbed the water, water again a little. You must repeat the process until water runs out from underneath and check the EC of this. This should be adjusted to the values  in this table (column EC), although, depending on the variety it may require more or less food, it is always better to be a little lower than to exceed these values. If they are above, you must wash the roots until the EC value is within the marked limits. You can also use Flush, a product specifically designed to clean the soil and roots of excess nutrients.

In mother earth it is more difficult for them to block, because the roots can spread over a much larger surface. In case you suspect it has happened, fill a pot with soil close to the plant and carry out the process described above. In case you have a very high EC, use Flush and do not feed the plants until the EC is correct or you check that the chlorosis has been solved.

Bad substrate

A poor quality substrate that does not dehydrate properly or does not retain nutrients well can cause many problems in our marijuana plants.

A substrate that retains too much moisture could produce rot in the root system, drastically reducing the health of our cannabis plants and therefore their performance. In case of a bad substrate, a large amount of yellow leaves will be seen throughout the marijuana plant, both in young and old.

We recommend reading the article on the best marijuana lands  if you want a quality substrate.

Lack of food

If your plants lack any element necessary for photosynthesis, it is impossible for them to do it, for which yellow leaves will appear on your marijuana plants. In addition, this will make them forage for their own leaves and wilt quickly. The problem usually happens in the growth phase, when they are creating the structure that will support the buds.

Vegetative growth is carried out with the help of large amounts of nitrogen, which is the most demanded by the plant at that time and can create deficiencies if not enough is available. It is essential that the plant develops correctly so that production is adequate. Here you can find a selection of the best fertilizers on the market for the growth phase.

Exceso or lack of irrigation

It is also a possible cause of the appearance of yellow leaves in our marijuana. This requires high and low humidity cycles in the substrate, without drying. If not, the plant cannot perform its functions correctly and can cause, once again, a shortage of some of the elements necessary to perform photosynthesis. In this case, the upper leaves and especially the new ones will appear with this coloration.

Lack of irrigation can also cause chlorosis, as there is no availability of water and therefore of nutrients dissolved in it, to feed the plant and carry out photosynthesis correctly. Our plants should always have a certain degree of humidity in the soil.

Take a look at our article on irrigation, here we explain how to know if you water a lot or a little and how to correct it.

Exposure to light

Another common cause that can lead to the appearance of yellow leaves in marijuana is low exposure to light. In case it is deficient, the first leaves to acquire this color will be the lower ones, since without light it is impossible for them to carry out photosynthesis. You will have to prune the lower branches and leaves that cannot reach the light and make sure that the position and height of the bulbs is correct in the case of indoor cultivation.

The excess light causes burning in the upper leaves although usually are simple to detect and figure out which caused. As in the previous case, you must check that the position of the foci is correct, take temperature measurements in the highest area of  the crop and try not to exceed 28o, from this temperature plants cannot photosynthesize. This in addition to causing the appearance of yellow leaves in marijuana will not allow optimal fattening of the buds.


Cold temperatures can make some plants transform into something even more beautiful, there are plants that dress in gold, violet, purple, red or very dark green colors. This usually happens at the end of flowering, when the production of chlorophyll is in reverse since it is no longer so necessary for the plant. As if they turn yellow, we have already commented that it is normal, but if this happens at the beginning of flowering we must be careful and check the temperatures both day and night of our crop. The equipment climate control are essential in any cultivation of cannabis, as is the way of knowing that the plant is in the range of physical conditions that will perform their functions properly.

PH level

Taking into account that the appearance of yellow leaves in marijuana grown under intensive conditions are related to nutrition and nutrient availability, we cannot forget one of the factors that limit this availability, pH. Depending on the level of acidity or alkalinity, our plants will be able to assimilate some elements and others not, it is very important, for the correct feeding and to avoid deficiencies that cause chlorosis, to have a pH adjusted between defined values. If you want to know more about the importance of regulating pH, we suggest reading the article What is the pH of water? How to measure and control it?