Growth fertilizers: What they are used for and how to use them
Plants grown outside their natural environment, for example indoors, in pots or in hydroponics, require careful attention and proper nutrition supplied by fertilizers. Fertilizers for the vegetative phase are rich in nitrogen and provide your plants with the nutrients needed for rapid growth and healthy root system development. We will advise you on how to choose the right fertilizer according to the growing medium, cultivation method and the plant's age.
While plants growing in open soil in nature or in garden beds can obtain nutrients naturally, when plants are grown in pots, soilless media or hydroponics they depend on fertilizers. These can be various types of organic, mineral or organo-mineral fertilizers in powder or liquid form with slow or fast release, depending on the growing medium, the species being grown and, not least, the age of the plant.
What is vegetative growth and the growth phase?
Annual plants go through several phases during their life cycle, which we can divide into vegetative growth phases and flowering (generative) phases. As plants transition from one stage of the life cycle to another, their nutrient requirements change. The amount of nutrients and the frequency of feeding will vary depending on the cultivation method, growing medium and species, but generally plants in vegetative growth need more nitrogen (N) and less phosphorus (P), while during generative phases they need less nitrogen (N) and a higher proportion of phosphorus (P).
Vegetative growth phases
- Germination/cutting
- Seedlings/rooting
- Vegetative growth
Flowering phases
- Start of flowering
- Mid-flowering/rapid flower development
- Maturation
Read also: NPK – what it is
Growth fertilizers for germination and cuttings
After germination
of seeds
the first pair of leaves appears on the plants, which we call cotyledons. These do not look like normal (true) leaves that will grow a little later. Cotyledons serve as a source of food and are not capable of photosynthesis. At this stage do not fertilize the plants; wait until several sets of true leaves have developed. You can help seedlings by treating them with a root stimulator or mycorrhiza support products.
Growth fertilizers for seedlings and young plants
Once the plants have produced the first 4–5 sets of true leaves, you can transplant them into a larger pot or growing container where they will remain for the rest of the vegetative cycle until harvest. Now begin supplying the plants with growth fertilizers with a high nitrogen content. You can also continue to apply root and growth stimulators. The choice of specific products depends primarily on your cultivation method and the nutrient program you have chosen. If you are just starting to grow, follow the dosing tables and do not mix products from different manufacturers.
Read also: Dry or liquid fertilizers, which are better for indoor growing?
Fertilizers for vegetative growth
At the peak of the vegetative phase and when transitioning to flowering, plants consume mainly nitrogen and require large amounts of water. The frequency of fertilizing and watering during the vegetative growth phase is influenced primarily by the growing medium.
When growing in soil it depends on whether you use pre-fertilized potting mixes or unamended (“light”) soil mixes. In the case of soil mixes enriched with organic or mineral fertilizers, plants may require only minimal or no additional fertilizer during the first weeks of growth. Fertilizers for growing in soil can be organic, mineral or organo-mineral, with fast or gradual release, in powder or liquid form.
Plants grown in coco substrates are entirely dependent on the nutrients you supply in the form of fertilizers. This is because coconut fibers contain very few nutrient elements that plants can absorb. Fertilizers for growing in coco can be organic, mineral or organo-mineral and are used to prepare the nutrient solution with which plants are watered regularly.
Soilless growing media (rockwool, perlite, clay pebbles) work best for hydroponics, where the plant roots are constantly immersed in the nutrient solution. Fertilizers for hydroponics are usually mineral and act very quickly, so regular measurement of the nutrient solution's pH and EC is important.
Read also: Guide to growing substrates