The pH is a measure of the acidity or the alkalinity of the solution. Normally the pH ranges from 0 to 14. A low pH (lower than 7) means that a solution is acidic. Pure water has a pH of around 7 which is neutral. Higher than 7 is called alkaline. Acidic solutions can be neutralised with alkaline solutions and vice versa. Too acidic is fatal for any plant and so is too alkaline. One of the causes is that the nutrients change into a, for the plant, unabsorbable form when the pH becomes too high or low.

The pH of the nutrient solution should be checked regularly with a pH meter. Take care with these acids because they are corrosive. The pH of a nutrient solution for growing your "favourite plant" should be between 5 and 7. Because rockwool is made from rock and rocks can be very alkaline, rockwool can also be very alkaline itself. This results in an immediate rise of the pH value of the nutrient solution as soon as it comes in contact with the rockwool. To minimize this effect, the rockwool slabs should be soaked in nutrient solution in which the pH has been adjusted to 5.3, at least 24 hours before using them (one slab will need ca.10 litres). After 24 hours, measure the pH in the slab again and adjust if necessary. The EC of this solution should be 1.7 ms. The soaking is an art. You must learn how heavy and/or moist the slab should be. When the slab is too wet the young plant will experience difficulties. The rockwool slab has then absorbed so much water that there is hardly any room left for oxygen. This results in a plant that dies from root rot.

This shows how important the use of Toprock grow blocks are. These rockwool grow blocks are structured vertically (Toprock slabs have a horizontal structure) which greatly improves drainage and stimulates a rapid, healthy root development. Take all of these factors into account because the first stage determines the later quality level and growth strength of the plant. We can only give guidelines in this because the pH of the tap water differs from town to town, and might even be different from the morning to the evening. Also the factor with which the pH in the slab changes might differ from place to place. During the growth period we use a pH of between 5.7 and 6.3 in the slab.

N.B: All accurate measurements need to be carried out in the slab. To provide for an average measurement of all the slabs, use the common drainwater.

It is advisable to buy a hypodermic syringe to suck the liquid out of the slab. (ca.50ml is enough for a sample, but make sure you pour it back where it came from). If for example the pH in the slab is 6.3 and you want it to be 6.8, then (6.3+0.5=6.8) you need to increase the pH in the reservoir with 0.5. So if for example the pH in the reservoir

is 5.4 you would have to make it 5.9. Between 7 and 14 days after the flowering period is initiated (the moment you change from 18 to 12 hours of light) you gradually reduce the pH in the slab to 6.0 which enables the plant to absorb more phosphorus. At this time you also change from CANNA Vega to CANNA Flores.


The EC is for many people just as the pH values - a twilight zone, although it is not that complicated. EC stands for Electro Conductivity and is measured in ms; conductivity of electricity in a liquid occurs through conductive particles. The nutrients (elements) that are necessary for your "favourite plants" become negatively and positively charged particles as soon as they dissolve. The more of these particles present, the better electricity is conducted, the higher the EC. Therefore the EC is a measure of the amount of nutrient present in a solution. CANNA nutrients are vital to the plant and because these nutrients are directly available, you must proceed very carefully.

A too high EC will produce a too high osmotic pressure around the roots. Osmosis? A liquid moves, according to physics, in the direction of the strongest solution. Is the solution outside the plant stronger than inside, then the plant empties itself (simply said). This emptying of the plant can be noticed in practice as a so called burning of the leaves. (When leaf blades curl down they are trying to conserve water).

In general we advise that the EC with TOPROCK rockwool lies between 1.6ms and 2.5ms. (Of course we talk about the EC in the slab). When making a nutrient solution always adjust the EC first and only then the pH value. This is because CANNA nutrients are very acidic and the addition of nutrient has a direct influence on the pH.

CANNA nutrients are sold in concentrated form and consist of different parts. These parts, A and B, are packaged in separate jerrycans. This is because the separate parts work negatively together in their concentrated forms. Therefore always ensure that when making a nutrient solution these concentrated part (A and B) never come in contact with each other. Mix part A with the water and only then add part B. If the packaging advises 1:250, then for example begin with a solution of 1:275, then after stirring thoroughly measure the EC and if necessary add some more to reach the correct value. Let the nutrient solution stand for approximately 2 hours (to work in) and then adjust the pH value.

Questions like how much feeding solution does my plant require in week 3 and how much in week 6 are impossible to answer. This is related to the size of the plant, the amount of leaves, height of the lamps, relative humidity, temperature, root development, ventilation per m/hour. The only good answer to this question is that you must learn to see how your plant feels and learn to feel the weight of the slab (to determine if it is wet enough). The EC you must use also depends on the requirements of the sort. When your plant looks healthy, fresh and green you are doing the right thing.