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
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.
Base nutrients just means essential plant
food. This is the regular "everyday" fertiliser that your plants
need to assimilate in order to grow and bloom.
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.
Additives 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."
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.
Organic 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
Liquid 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.
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
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 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 (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
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 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
- 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
- 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
A Final Word on "Specialist" and "Premium" Hydroponic
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
"Well, I am using coco coir, so I need some coco-specific
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.