Fertilisers and Nutrients for Cannabis

Nutrients, or fertilisers, in our niche at least, refer to ‘food for plants’. Cannabis plants need a certain quantity and type of food in order to grow to their best potential. The main nutrients in cannabis nutrients are Nitrogen (N), Phosphorus (P), and Potassium (K).

In addition to these main nutrients, cannabis plants require a lesser amount of ‘secondary’ nutrients and trace quantities of other elements.

Secondary nutrients are calcium (Ca), sulphur (S), and magnesium (Mg). Trace elements are small quantities of boron, chlorine, cobalt, copper, iron, manganese, molybdenum, and zinc. (Add appropriate symbol 🙂 )

Cannabis fertilisers are always calculated in the N-P-K format; as above, N is Nitrogen, P is Phosphorus, K is Potassium.

So a nutrient/fertiliser. Soil that displays an NPK ratio of 20-10-10 plant food contains 20% Nitrogen, 10% Phosphorus and 10% Potassium.

You get the picture?

The remaining 60% in this case is made up of secondary nutrients, trace elements and inert materials.

A good quality nutrient soil/fertiliser with secondary nutrients and trace elements will get you through all stages of growth. But during the different stages of growth you can, if suitable, change the nutrient levels to suit individual strains.

Nutrient Requirements

Seedlings

Regardless of the nutrient soil/fertiliser you choose, during the first 1-2 weeks of life and the first 1-2 weeks of flowering, use half the amount (or less) of nutrient solution the manufacturer recommends; i.e. if their packaging says use 10ml per gallon of water, then use just 5ml per gallon of water for these first few weeks of the stages. It is essential to not over feed then when they are young. Most times we ourselves will give them no additives with their water for the first few weeks.

Veg stage

During seedling/vegetative growth the plants need lots of N (nitrogen). They also need a fair amount of P (phosphorus) and K (potassium), 20-10-10 in our scenario or something with these similar ratios of N-P-K, and secondary nutrients, and trace elements will be good.

Flowering

During flowering the plants need more P (phosphorus) and more K (potassium) than they did during vegetative growth. They need some N (nitrogen) but not as much as they did during the veg stage. They still also require their secondary nutrients and trace elements.

If you used 20-10-10, as in our scenario, for the veg stage then try using 10-20-20 for flowering.

Easy Does It

Do not give your plants extra nutes thinking it will make them grow faster. Too much will kill your plants. If you under feed, plant growth will be slowed down but they will stay alive far longer than if you feed them too much. Follow the mixing instructions on your soil nutrient package, if you aren’t sure, err on the side of caution.

Stop feeding the cannabis plants at least 14 days before harvesting when growing in soil. The last few times you water the plants, don’t add any nutrients at all. Pure water if perfect. This is so the mentioned elements N, P and K etc can be used up by the plant before harvesting. This will help the cannabis in several ways, a better taste, healthier and a better burn.

Buying Nutrient Based Soils

Most companies that make these soils specifically for cannabis nowadays offer their ranges with different nutrient ratio’s, aimed at both stages of growth, the vegetative stage and the flowering stage. So as we often do, simply look for the two combinations from your choice of company.

Two and three part nutrient solutions, that allow you to custom blend the amount of the different components, are highly recommended to experienced growers. Organic nutrients are available and highly recommended, they produce the best cannabis as far as we are concerned, along with the obvious green benefits but they can be harder to find, and expensive. We personally always use bio products if possible.

Paz’s Conclusion

One of the biggest problems I see inexperienced (and many apparently experienced too) growers have is over feeding. Ignorant to the fact that their plants could be twice as good if they fed at about 30% of most manufacturers recommended dosages.I experiment of course, products such as Canna’s Bio Vega in vegetation stage and in flowering GH’s FloraNova Bloom or Bio Canabium’s Floracion. Much of my growing is based om ‘old skool’ organic products such as worm humus, algae and bird guano with the bottled or powdered feeds supplementing these as oppose to the other way around.

Don’t forget, our friendss over at Alchimia offer the great range of nutes, and have a great service.