Cannabis Seeds FAQ - How Do I Feed A Plant?
Although this may seem like a really obvious question (just add water.. duh) there is more than meets the eye when it comes to feeding plants. The most important aspects here are the pH (potential of hydrogen, or the acidity/alkalinity of water) and EC (Electrical Conductivity, or the amount of mineral salts present in the water). You may have heard around the grapevine that Cannabis has the same nutritional needs as Tomatoes... This is not entirely true.
How do I feed a plant doesn't change, its how much to feed the plant!
Tomatoes are considered a "greedy" plant that can take any amount of nutrients, represented in higher amounts of EC in the water, where as Cannabis is more finicky. If you overfeed the plant it will react to this excess through its leaves in the form of nutrient burn so it is advisable to keep a very tight control on this aspect.
Usually feeds and fertilisers will have a suggested dosage according to the phase the plant is in, this way if you do not have an EC meter or are not sure of the level you want, this is a safe enough way to go. With regards to the pH, the water has to be between 6-6.5 for best results.
In Amsterdam, the pH of tap water varies between 7.5-7.9 which is too alkaline, which means the use of pH- is advised for optimum water absorption by the plant, although there are some cases in which plants get used to the higher pH levels and can do without the increase in acidity.
A clear symptom of high pH is when the tips of the leaves appear burnt while the whole leaf remains intact.
You might also find our FAQ Submission How Do I Germinate A Seed? useful