Plant Nutrition and Growth Enhancers

Beginners' Corner: Demystifying Plant Nutrients

Indoor gardening and hydroponics stores give up a whole lot of space for those pretty bottles we know and love as nutrients and additives. So here's our crash course for complete beginners.

Okay, so the plant nutrient world is vast and colorful. And no wonder-there's a lot of money to be made for the manufacturers! Indoor gardeners probably spend more on plant food and potions than anything else. Unlike reflectors and control gear (which hopefully you only buy or upgrade once or twice) sundry items such as nutrients and additives are perenially on the indoor gardener's shopping list.

We're going to assume you know nothing and then take you through the various product categories to help you make sense of all those bottles in the grow store. We're going to try and keep things brief and punchy and drill down one level at a time.

Base Nutrients, Boosters, and Addives

So, here is our top level division. Every bottle you buy from a grow store should fit into one of these categories.

Three part hydroponic nutrientBase nutrients just means essential plant food. This is the regular "everyday" fertiliser that your plants need to assimilate in order to grow and bloom.

Mineral booster to supplement phosphorus and potassium during flowering and fruitingMineral Boosters tend to also be just plant food, but designed to be used at specific times in the plant lifecycle. Boosters that provide extra phosphorus and potassium (known as PK boosters) are most common. There are other types of boosters that can enhance the availability of your base nutrients (rather than add to them) - this is especially applicable to organic products.

Fulvic acid additiveAdditives covers just about everything else. Enzyme products, acidity adjusters (to move the pH of your nutrient solution up and down), wetting agents, mycorhizae, vitamins, humic acids, fulvic acids, you name it. Here we use "additives" to cover "everything else." 

Base Nutrients

Mineral Based Nutrients are plant foods made from special combinations of refined mineral salts. They are also known (less lovingly) as chemical feeds, inorganic nutrients and synthetic nutrients. Crucially, plants can access the elements they need directly without any need for assimilation. Mineral base nutrients are available in liquid form or granules. They come in highly concentrated form so must be diluted with large amounts of water in order to create a nutrient solution that's safe to feed to your plants.

Premium organic liquid feedOrganic Nutrients - it's probably more accurate to say "organic inputs." These are designed for use with soil (although some growers have reported success with coco coir) and are also available in liquid or granule form. Organic inputs are largely naturally-occurring unrefined materials that will fertilize plants through the action of microbial mineralization. These organic fertilizers include sugar beet extracts, worm castings, guano, animal manures, compost, blood meal, bone meal, fish products (meal/emulsion/hydrolysate), alfalfa meal, feather meal, seaweed, unrefined naturally occurring minerals (glacial rock dust, soft rock phosphate, Epsom salts) and many, many more. Solid organic inputs can be mixed into the potting mix before planting or 'top dressed' on the surface after planting for gradual absorption.

Premium organic liquid feedLiquid organic nutrients are manufactured according to a complex process that involves the selection of key ingredients that will stay stable and soluble. These are added to water just like mineral based nutrients. Liquid organic nutrients are generally not recommened for dripper systems as they tend to clog the tubes after a while.

One part hybrid nutrientHybrid Nutrients are plant food products that (you guessed it) mix the "best of both" - organics and mineral.

Mineral Based Nutrients

Hydroponics - As far back as 1860, a German botanist called Julius Sachs demonstrated that plants could be grown in a specially prepared "nutrient solution" with no soil in the equation at all. 

Of course, take away soil and this nutrient solution has to be all-encompassing. It has to provide all the minerals a plant needs, totally replacing the elements it would normally get from the soil. This technique of total soil replacement is commonly referred to as hydroponics.

Mineral based nutrients designed for hydroponics provide the "full spectrum" of minerals a plant requires, in a form they can readily absorb, and in the right amounts / ratios.

General Purpose (Soil) -  these mineral based products are designed for use with soil only. They have been formulated to supplement the minerals commonly found in soil. It's this latter type that you will often find in the big box gardening stores. If you try to save some bucks and use these products in your hydroponics system you may well encounter some plant nutrition problems further down the line.


One part hybrid nutrientOne Part

One part nutrients are preferred by some growers simply because of their ease of application. After all, you only have to measure one thing once! All the minerals your plants need are delivered in precisely the right ratios in one bottle.

One part nutrient products often come in two bottles though! One is a "grow" formulation for use when plants are producing stems and leaves, the other is a "bloom" formulation for use when plants are producing buds, flowers and fruit. This is because a plant's nutritional requirements change during its lifecycle.

Two part hydroponic nutrientTwo Part (A and B)

Two part (A and B) nutrient products are really four parts! You have two bottles for the grow stage (Grow A and B) and two bottles for the bloom stage (Bloom A and B.) 

By splitting the grow and bloom formulations into two components for each, manufacturers can separate volatile elements and produce nutrients at higher concentrations. This means the grower uses less product to make their nutrient solution.

The golden rule when using multi-part nutrient products is to stir in the 'A' part thoroughly into your water reservoir before stirring in the 'B' otherwise the nutrients will not dissolve properly and precipitate out of the solution making some important elements unavailable to your plants. Equal parts of 'A' and 'B' are used.

Two Part (Duo) NutrientTwo Part (Duo)

This is a true two-part nutrient - just two bottles for the complete plant lifecycle. The trick here is the ratios the grower uses. For the grow / vegetative phase you use a different ratio (according to the manufacturer's instructions) of the 'A' and 'B' than for the bloom phase.

Three part hydroponic nutrientThree Part

Three part nutrient products give the grower the most control. Arguably there's the greatest risk for error, but if you're reasonably confident in your label-reading and measuring abilities there really isn't much cause for concern here.

There are three bottles: Grow, Micro and Bloom. The idea, similar to Two Part (Duo), is that the grower uses different ratios for different parts of the plant lifecycle. 

Most growers mix in the Micro component first and stir well and then add the Grow and Bloom components, stirring thoroughly after each addition.

Mixing Tips

  • Mix your nutrient solution in a large reservoir, preferably 25 gallons or more.
  • Measure the pH and EC (electrical conductivity) of you water before you add anything to it. This gives you an idea of where you're starting out from! The lower the EC of your water, the better.
  • Don't mix your nutrients in ice cold water. Ideally the water should be tepid, at around 64 °F (18 °C) - it should feel silky (neither warm or cold) to the touch.
  • Stir really well after adding each component. Never add different parts of a nutrient product together in concentrated form - they are separate for a reason!
  • Leave your nutrient solution to stand for ten minutes before testing the pH and EC again.
  • Use an air diffuser to bubble air into your nutrient solution to increase levels of dissolved oxygen.
  • Aim for a pH of between 5.5 and 6.5. Use a pH adjuster if necessary. Always dilute your pH adjuster with water (100 parts water to 1 part pH adjuster) before adding to your nutrient solution. Not only does this make application easier, but it minimizes the risk of strong acids or alkalines precipitating nutritional elements out of your solution.


One final option for hydroponic nutrient products is whether they are designed for use with a substrate (i.e. rockwool, coco coir, clay balls, etc.) or for use in a totally aqueous environment (NFT, DWC) where a substrate isn't used at all - i.e. the plants are grown directly in the nutrient solution itself.

For the most part, you really don't need to worry though! Hydroponic nutrients will work just fine in all hydroponic situations.

A Final Word on "Specialist" and "Premium" Hydroponic Nutrients

If that bottle of hydroponic nutrients you're sizing up in the store features pretty labels of scantily-clad ladies, fat cigars, sports cars or expensive jewellery... you might want to move right along! No doubt the price tag will dent your cigar / car / jewellery budget anyway! 

Look for an established brand with a widely-recognized reputation. 

"Well, I am using coco coir, so I need some coco-specific nutrients, right?"

No, actually you don't. All you need is good quality coco coir (with the majority of the salts removed) and add some Calcium/Magnesium (ask for a "Cal/Mag" product at your local grow store.) Most coco-specific nutrients and only slightly increased in cal/mag and sometimes lessened in nitrogen - no big deal.

Of course, if you only grow in coco coir then perhaps investing in a coco coir specific formulation makes your life easier.