Postbus 169, 3400AD
IJsselstein, Netherlands



Frequently Asked Questions

Growers often see purple petioles on plants.

These purple stems are only due to one thing, and that is a phosphorus deficiency.

Phosphorus is the second important building block of the plant, and a deficiency of this results in a different chemical reaction of nitrogen in the plant.

The causes of the phosphorus deficiency can be:

  • Cold. At a temperature below 20 ° C, phosphorus travels less in the plant and almost no longer at all below 17 ° C. The phosphorus simply stops, causing a shortage. The plant therefore hardly grows below 17 ° C. Note: A plant also grows at night and the temperature should never be lower than 20 ° C. Every time the temperature drops below it means a loss in the end yield.
  • Too high pH. If the pH in the medium rises above 6.0, the phosphorus decreases included. If the pH in the medium rises above 6.5, phosphorus is almost completely not recorded.
  • Poor plant nutrition. Phosphorus comes in all kinds of different qualities and that has to do with the origin of the nutrient (what the phosphorus is made of). The quality determines the absorbability, concentration and miscibility. Most food suppliers use cheaper phosphorus, which means that high concentrations are not possible and they quickly bind with other substances. Think of: crystallization, gypsuming and crusts on the medium. Deficiencies are often supplemented by using a phosphoric acid as a pH.
We often also see a phosphorus deficiency and therefore purple stems in mother plants because the grower uses a nitric acid as pH-. Some competitors market this as a growth pH. This is completely incorrect, especially if you use the nutrition of those same competitors.

Leaves that are burnt and lighter in color is a common problem. Most common cause: pH too high or too low. Because a pH in a medium, for example, falls below 5.2 or above 6.0, it happens that many different salts can no longer be absorbed by the plant. The greater the deviation from the ideal pH, the less the absorption. The plant becomes deficient and lighter in color. However, during all this time, people have been given feeding sessions, so that the concentration of food salts has increasingly accumulated. In the long run one gets too great an osmosis imbalance, which will be compensated by withdrawing water from the leaf back into the medium. This phenomenon is also called leaf burning (burning leaves). A first warning for burnt leaves is often the curling up or the yellowing of the leaf edge. The plant notices the equilibrium difference with the medium and is the first reaction to close the stomata on the outside of the underside of the leaf.

A common problem with indoor cultivation is that the fruit set becomes harder, but does not want to grow. Growers spend a power on extraction and ventilation equipment, but sometimes forget that what goes out must also come in again. Usually they have a too small blow-in opposite the extraction or no blow-in at all but a small opening somewhere underneath. In this way you create too much underpressure and the plants crave fresh air (CO2), as it were. If the door was left a wide open for a week, the plants will grow almost twice as large after this week. Just the correct blowing capacity or a much larger intake hole is best for this problem.

Shortages, heat. Growers sometimes find that they are growing volume with little content. This usually occurs in climates where the temperature around the leaf is 32 ° C or higher or the light is very poor. The plant grows outwards, as it were ... If the temperature is too high, simply lower the temperature or allow the plant to cool more by lowering the Ec. When the plant is too hot, it wants to cool more. The plant does this by evaporating more water. However, if this is not possible because the medium is too dry or there is too much nutrition in the medium, the plant will create surface in order to be able to cool in that way. The best solution for this is to reduce the Ec by half with heat. The plant will then drink and evaporate much more to cool down and still get its amount of nutrition. This also depends on the genetics of the plant, of course, one plant is more sensitive than the other plant. If the pH is good and the Ec before watering is quite low, you can increase the Ec of the watering. Even if the nutrient uptake has somehow stagnated or the plant simply simply needs more than is present, the plant can increase in volume.

Leaf problem picture Many growers often see that the sides of their leaves usually curl up at the top. Metrop Stomata with which the plants breathe are located on the underside of the leaf. These stomata must allow water to evaporate for the absorption of nutrients and water. However, if there is a disturbance that causes a plant to evaporate less water, the plant closes a number of these stomata on the outside of the leaf. You will then see the leaf edge curling up slightly. The greater the disturbance, the more stomata close and the further the leaf curls. The causes of the faults can be:

  • Too much evaporation under the leaf. If by means of heat, low humidity or a fan that is placed too hard on the plant can evaporate the plant more than it can absorb again.
  • Too many salts in the medium by means of overfeeding or the wrong pH. The medium then wants to compensate for the imbalance of salts in the plant and outside the plant (medium) by retaining water, or even withdrawing it from the leaf (leaf burning). The leaf then receives little or no new moisture and it closes the stomata to avoid losing new moisture.
  • A shortage of air in the medium hinders the movement of elements. Curly leaves are always an indication for the grower to take action.

Metrop Metrop Metrop
PO Box 169
IJsselstein , UTRECHT , 3400AD Holland