Fertilizers: Complete Guide to Buying Nutrients for Your Plants

How to choose fertilizers: A complete buying guide to nutrients for your plants

There are dozens of brands and hundreds of different types of fertilizers on the market – in liquid, powdered and solid form, organic and mineral, for different growth stages and cultivation methods. How do you make sense of it all and avoid mistakes? We have prepared an overview of the main fertilizer types and practical advice to help you choose the right nutrition for your plants.

Main fertilizer types by growing medium

There is a difference between fertilizers for growing in soil, coco, inert substrates or hydroponics. Before you start buying fertilizer, be clear about which substrate and cultivation method you will use. Only then choose the appropriate type of nutrition.

• Fertilizers for soil: Suitable for growing in open soil (beds) or in pots.
• Fertilizers for coconut substrates: Coconut fiber substrates themselves do not contain nutrients and require special fertilization. Coco substrates are typically used for indoor cultivation or in greenhouses.
• Fertilizers for hydroponics: Designed for preparing nutrient solutions for soilless systems or when growing in inert media such as rockwool.

You might be interested in: Guide to growing substrates

Choosing fertilizer by growth stage

From germination to harvest, plants go through several growth stages and their nutrient needs change accordingly. During the first weeks they need little or no fertilization; during the vegetative phase it is important to provide sufficient nitrogen, and during flowering it is appropriate to use fertilizers with increased potassium and phosphorus.

• Starter fertilizers - Start: Contain small amounts of nutrients and often substances to support root growth and beneficial microorganisms, such as mycorrhizal fungi or soil bacteria.
• Fertilizers for the growth phase - Grow: Contain increased amounts of nitrogen, which plants need for producing leaves and stems. Nitrogenous fertilizers can be purely organic, mineral or combined, and nitrogen can be present as nitrates (NO₃-) or ammonium (NH₄+), which affects uptake speed and can influence substrate pH fluctuations.
• Flowering fertilizers - Bloom: Contain higher amounts of phosphorus and potassium to support flower and fruit production and, like other fertilizer types, can be organic, mineral or combined.
• Pre-harvest fertilizers - Flush: Especially when growing medicinal plants, some growers stop using fertilizers several weeks before harvest and replace them with plain water or special flushing fertilizers or finishers. The goal is improved aroma and taste of the final product.

You might be interested in: What NPK fertilizers are and what they are used for

Organic vs. mineral fertilizers

Although plants themselves do not care about the source of nutrients absorbed by their roots, the difference between organic and mineral fertilizers is significant in cultivation. Organic fertilizers are effective only in the presence of soil microorganisms and are therefore suitable primarily for growing in soil (organic) substrates or in garden beds. Synthetic fertilizers contain mineral salts that plants can absorb directly from water and can be used for growing in coco, inert substrates and hydroponics.

• Organic fertilizers: Made from natural materials such as compost, manure, bone meal, guano, fish, seaweed or plant extracts. Bear in mind that organic fertilizers take some time to become effective.
• Mineral fertilizers: Contain nutrients in the form of mineral salts obtained from phosphates, ammonia and nitrogen synthesized from the air. They act immediately and carry a risk of over-fertilization. Always follow dosing charts and measure the pH and EC of the nutrient solution.

You might be interested in: Organic vs. synthetic fertilizers: Which is better for your plants?

Fertilizer form: liquid, solid or powdered?

Fertilizers can come in several physical forms – from fully liquid to granular or solid slow-release products. Each form has advantages depending on where and how you grow. Different forms can be organic, mineral or combined.

• Liquid fertilizers: Concentrated nutrient solutions for preparing feed are the most user-friendly. They act quickly, are easy to work with and have long shelf life.
• Dry fertilizers: Water-soluble fertilizers in powder or granule form can be used to prepare nutrient solutions or applied directly to the substrate (if formulated for that use).
• Slow-release solid fertilizers: Pellet or granule fertilizers with slow release are suitable for outdoor growing because they leach from the soil more slowly and supply nutrients gradually. The downside is that they are harder to dose.

You might be interested in: Dry vs. liquid fertilizers — which is better for growing?

Complete nutrition: multi-part vs. single-component fertilizers

Especially for hydroponic growing, it is common to use multi-part fertilizers that are mixed in proportions to create the ideal nutrient solution for a specific situation (for example more nitrogen during the growth phase or more phosphorus and potassium during flowering). On the other hand, single-component fertilizers contain a fixed nutrient ratio, usually formulated for a specific growth stage (veg/flower).

Supplements and growth stimulators

In addition to base fertilizers that contain the macro- and micronutrients necessary for plant growth, growers will also find a range of supplemental nutrition and growth stimulators on store shelves. These additives are not usually strictly necessary, but many growers use them to pamper their plants to perfection.

• Root stimulators: Speed up root formation and are used during germination, cloning or transplanting.
• Growth and bloom boosters: Stimulate plants to produce more leaves or flowers.
• Vitalizers and enzymes: Various additives for stress protection and support of microbial life.

You might be interested in: When and how to use root stimulators

Now you should be ready to purchase appropriate fertilizers for your plants. Before you go, we’ll add a few final tips.

Avoid mixing brands: Different manufacturers use different formulations that may not be compatible.

Use a pH and EC meter: Measuring the pH and EC of the nutrient solution or substrate gives you a clearer picture of nutrient levels in the root zone.

Fertilize regularly: Plants benefit from a steady and stable supply of nutrients. Don’t wait to fertilize until nutrient deficiencies appear.

Not sure which fertilizers to choose or just starting out? Useful information for beginner and experienced growers can be found on our Higarden blog or get in touch with our sales team.