How to Choose Fertilizer: Complete Guide to Buying Nutrients for Your Plants

You can find 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 and avoid mistakes? We have prepared an overview of the basic types of fertilizers and practical advice to help you choose the right nutrition for your plants.

Basic types of fertilizers by growing medium

There is a difference between fertilizers for growing in soil, coco, inert substrates or hydroponics. Before you go shopping for fertilizer, clarify which substrate and which method you want to use to grow your plants. Only then will you 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 growing substrates themselves do not contain nutrients and require special fertilization. Coco substrates are typically used in indoor growing or in greenhouses.
• Fertilizers for hydroponics: Intended for preparing nutrient solutions for soilless systems or when growing in inert media such as rockwool.

You may 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 of life they need little or no feeding, during the vegetative stage it is important to provide enough nitrogen, and during flowering it is appropriate to use fertilizers with increased potassium and phosphorus content.

• 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 vegetative stage - Grow: Contain an increased amount of nitrogen, which plants need to form leaves and stems. Nitrogen fertilizers can be purely organic, mineral or combined, and nitrogen may be present as nitrates (NO₃-) or ammonium (NH₄+), which affects uptake speed and influences substrate pH fluctuations.
• Fertilizers for flowering - Bloom: Contain higher amounts of phosphorus and potassium to support the formation of flowers and fruit, and like other fertilizer types can be organic, mineral or combined.
• Pre-harvest fertilizers - Flush: Especially when growing medicinal plants, some growers replace fertilizers with plain water or special flushing/finishing fertilizers a few weeks before harvest. The goal is better aroma and flavor of the final product.

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

Organic vs. mineral fertilizers

Although plants do not care about the source of the nutrients their roots absorb, 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 only for growing in soil (organic) substrates or in 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. Keep 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 synthesized nitrogen from the air. They act immediately and carry a risk of overfeeding. Always follow dosing charts and measure the pH and EC of the feed.

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

Fertilizer form: liquid, solid or powdered?

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

• Liquid fertilizers: Concentrated fertilizer solutions for preparing feed are the most user-friendly. They act quickly, are easy to work with and have a long shelf life.
• Dry fertilizers: Water-soluble fertilizers in powder or pellet form can be used to prepare nutrient solution or applied directly to the substrate (if designed for that).
• Slow-release solid fertilizers: Pellets or granules 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 may be interested in: Dry vs. liquid fertilizers — which are better for growing?

Comprehensive nutrition: multi-part vs single-part fertilizers

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

Supplemental nutrition and stimulators

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

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

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

You should now be ready to buy the appropriate fertilizers for your plants. Before you go, we’ll add a few final tips.

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

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

Feed regularly: Plants benefit from a steady and stable supply of nutrients. Do not postpone feeding until nutrient deficiency appears.

Not sure which fertilizers to choose or just starting out? Useful information for beginner growers and experienced growers can be found on our Higarden blog or contact our sellers.