Your system is set up.
You’ve got your seedlings.
And you’ve promised your wife an organic, homegrown meal for her birthday three months from now.
You’d better nail your nutrient mix.
What is a hydroponic nutrient mix?
A hydroponic nutrient mix is a water-based mixture of all the stuff plants need to thrive in your hydroponic system.
In standard soil gardening, plants get much of their nutrition from the topsoil with gardeners supplementing the soil with fertilizer to give their plant everything they need.
But in hydroponic systems, there is no soil, and that means there are no nutrients (aside from some dissolved ions in your local tap water). You need to add everything.
While this can seem daunting, it’s actually an awesome opportunity for you to create the best possible growing environment for your plants.
It’s completely customizable, contained, and controllable.
Your hydroponic nutrient mix is critically important
You don’t see many marathoners chowing down on McDonald’s quarter-pounders before their weekend long runs, because to achieve their desired results, they need to feed their bodies the right mix of nutrients.
The same goes for your hydroponic plants.
It doesn’t matter…
- How efficient your LED lights are.
- How precise your ebb and flow schedule is.
If you’re depriving your plants of essential nutrients, they won’t reach their potential.
Many hydroponic farmers are intimidated by putting together the best nutrient mix for their system, and it’s completely understanable:
- You can’t see nutrients like you can see your lights or airstone.
- And let’s face it–chemistry class was a long time ago.
But in reality, understanding the nutrients plants need is pretty simple.
This guide has everything you need to know explained in plain English. I recommend you bookmark this page and reference it as needed (CTRL + D on a PC).
Let’s start with the basics.
16 Nutrients Your Plants Need
Plants need 16 essential nutrients to grow, and they can be put into four major groups:
- 3 environmental nutrients
- 3 primary nutrients
- 3 secondary nutrients
- 7 micronutrients
| Category | Nutrients | Supplied By |
|---|---|---|
| Environmental | Carbon, Oxygen, Hydrogen | Air, Water |
| Primary | Nitrogen, Phosphorus, Potassium | NPK Fertilizer Mix |
| Secondary | Calcium, Magnesium, Sulfur | Epsom Salt, Calcium Nitrate |
| Micronutrients | Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Zinc | Seed |
Let’s take a look at what each nutrient does.
3 Environmental Nutrients
Environmental nutrients come from the air and water and don’t need to be provided as part of a nutrient solution.
- Carbon (C) is the primary building material for leaves, roots, and stems.
- Oxygen (O) is an essential part of glucose production, which is used for energy in nutrient uptake by roots.
- Hydrogen (H) aids in proton gradients, which are essential for the electron transport chain in photosynthesis, and is part of nearly every compound.
3 Primary Nutrients
Primary nutrients need to be supplied as part of an NPK (nitrogen-phosphorus-potassium) fertilizer. Some plants have different NPK requirements, and each stage of the growth cycle (such as root development or flowering) may have different NPK needs as well.
- Nitrogen (N) is a major component of several essential compounds, such as chlorophyll and amino acids. It promotes structural and vegetative growth of stems and leaves.
- Phosphorus (P) is a vital component of ATP (used for energy), holds DNA and RNA together, and has several other major uses. It promotes root and fruit growth.
- Potassium (K) regulates the opening and closing of stomata during photosynthesis. It promotes general plant growth.
3 Secondary Nutrients
Secondary nutrients are required in smaller quantities than the primary nutrients above and can be supplied by calcium nitrate (calcium) and Epsom salt (magnesium and sulfur).
- Calcium (Ca) strengthens cell walls and aids in water movement.
- Magnesium (Mg) is a central component of chlorophyll and works as a phosphorus carrier.
- Sulfur (S) is a major building block of both amino acids and chlorophyll.
7 Micronutrients
Micronutrients are required in trace amounts and don’t need to be added to a nutrient mix. Generally, the seed from which a plant germinates has enough of these nutrients to sustain the plant for its entire life cycle. However, if you grow several generations from a starter seed and don’t replenish these nutrients, your plants will begin to suffer. Micronutrient deficiencies should be handled as issues arise. Check out this guide for warning signs that your plants may be deficient in one or more essential micronutrients.
- Boron (B) enhances structural integrity of the cell wall.
- Chlorine (Cl) is involved in the opening and closing of stomata during photosynthesis.
- Copper (Cu) is involved in enzyme activation and the metabolism of both carbohydrates and proteins.
- Iron (Fe) is a major component of chloroplasts, which produce chlorophyll.
- Manganese (Mn) is required for chloroplast formation and nitrogen assimilation but also important for pollen germination and root disease resistance.
- Molybdenum (Mo) is crucial for production of two enzymes responsible for the uptake of nitrate from the soil and nitrogen from the atmosphere.
- Zinc (Zn) is a key component of many enzymes and proteins.
NPK Mix + Epsom Salt + Calcium Nitrate
There are three parts to a complete nutrient mix:
- NPK mix: Supplies nitrogen (N), phorphorus (P), and potassium (K)
- Epsom salt: Supplies magnesium (Mg) and sulfur (S)
- Calcium nitrate: Supplies calcium (Ca)
NPK mixes are described using three numbers like 10-10-10. This expresses the ratio of nitrogen-phosphorus-potassium by weight, so a 10-10-10 solution is 10% nitrogen by weight, 10% phosphorus by weight, and 10% potassium by weight. A 5-30-20 NPK mix is 5% nitrogen, 30% phosphorus, and 20% potassium.
Ratios vary depending on two factors:
- The stage of growth
- The plants you’re growing
Let’s look at those for a moment.
Different stages of growth have different nutrient needs
Let’s take another look at tomatoes and the three nutrients in an NPK mix:
- Nitrogen: Helps the stem and leaves grow
- Phosphorus: Helps the roots and fruit grow
- Potassium: Aids in photosynthesis for rapid overall growth
Early in their life cycle, tomato plants need a lot of potassium (for efficient photosynthesis) and nitrogen (for leaf development) with added phosphorus for their roots.
As plants hit their primary growth phase with roots sufficiently developed, nitrogen becomes more important and phosphorus less. This emphasizes stem and leaf growth.
Finally, as tomato plants enter the flowering and fruiting phase, you want to cut back on nitrogen and increase both phosphorus and potassium. This emphasizes fruit development and prevents your plants from wasting their energy growing more stems and leaves.
General Hydroponics creates an easy three-part nutrient series that makes this whole process simple:
- FloraGro (0-5-4) for fast, early development.
- FloraMicro (5-0-1) for rapid vegetative expansion.
- FloraBloom (2-1-6) for fruit-focused growth.
But the FloraSeries isn’t the best option for all types of plants because…
Different plants have different nutrient needs
Think about tomatoes vs lettuce for a minute.
Both are delicious, and they’re both staples of a delicious summer salad, but they’re very different types of plants.
- Tomato gardeners focus on growing big, juicy fruit.
- Lettuce is all about the greenery.
Remember what we said about how each nutrient in an NPK mix helps the plant grow?
No? OK, well here it is again:
- Nitrogen: Helps the stem and leaves grow
- Phosphorus: Helps the roots and fruit grow
- Potassium: Aids in photosynthesis for rapid overall growth
I highlighted the most important distinction above.
Lettuce doesn’t have fruit!
Lettuce is all green, vegetative growth. As such, we don’t care about making sure lettuce focuses its energy on fruiting. We want to boost its ability to grow lots of greenery.
While General Hydroponics’ FloraSeries is great for many plants, it isn’t great for lettuce. We want something that’s high in nitrogen and potassium but low in phosphorus. Their MaxiGrow is 10-5-14 and delivers everything you need for robust lettuce growth.
Suggested nutrient concentrations for 6 common plants
Smart Fertilizer has a handy guide to common nutrient concentrations for six common plants. If you’re looking to customize your own hydroponic nutrient mix, this is a good place to start.
Note: All concentrations below are in mg/L, also known as parts per million (ppm).
| Plant | Nitrogen (N) | Phosphorus (P) | Potassium (K) | Calcium (Ca) | Magnesium (Mg) |
|---|---|---|---|---|---|
| Tomato | 190 | 40 | 310 | 150 | 45 |
| Cucumber | 200 | 40 | 280 | 140 | 40 |
| Pepper | 190 | 45 | 285 | 130 | 40 |
| Strawberry | 50 | 25 | 150 | 65 | 20 |
| Melon | 200 | 45 | 285 | 115 | 30 |
| Roses | 170 | 45 | 285 | 120 | 40 |
Note: These are just general concentrations. Remember that plants need different nutrients at different stages, so play around with these concentrations to find a set of mixes that works for you.
Wet vs Dry Fertilizer
For non-commercial farmers, liquid nutrients like the FloraSeries are the easiest way to feed your plants, but they aren’t the only option.
You can also purchase dry (or powdered) nutrients.
Typically, wet vs dry comes down to your size:
- Small-time hydroponics hobbyists generally opt for wet.
- Large-scale commercial farmers go dry.
The reason why is simple.
Advantages of Wet Fertilizer
Wet fertilizer comes with all of the nutrients already dissolved in water, which makes it incredibly easy to use. Unfortunately, because wet fertilizer already is dissolved in water, you’re paying for that water.
(And it’s a lot of water. You only mix a few teaspoons of dry nutrient mix per gallon of water.)
If you’re ordering online, that’s extra weight and higher shipping costs.
Advantages of Dry Fertilizer
Dry fertilizers comes as a powder that you need to mix yourself, but it offers one major advantage: It’s more economical cost-wise.
For that reason, almost all commercial growers use dry fertilizer.
Final Thoughts on Hydroponic Nutrients
Mixing your own hydroponic nutrient solution can be daunting, especially because of how important it is, but it doesn’t have to be hard.
Tons of great companies exist with pre-mixed liquid nutrient solutions for nearly any hydroponics application:
- General Hydroponics
- General Organics
- Advanced Nutrients
- Fox Farm
- Remo Nutrients
- House and Garden Nutrients
And many others.
But if you’re the DIY type and want to mix your own solution, great! Let us know what works for you in the comments section below.
