As hydroponic gardeners, one of the biggest advantages we have over soil-based cultivation is the ability to provide specific plant nutrients at the time when they need them most. This is why hydroponic crops can hugely outperform soil crops. Can is the important word in that last sentence. If you want to grow the biggest, baddest plants on the block, you gotta know how to feed them!
The hydroponic nutrient market doesn’t make this easy. There’s marketing hype, products you probably don’t need, and lots of confusing numbers. This guide isn’t going to get super sciencey, but it doesn’t have to in order for you to get those prize-winning yields you’ve been dreaming about.
Instead, let’s cover the basics and understand what our plants need throughout their growing cycles so we can cut through the marketing hype and focus on gardening greatness! Or…. at the very least, save ourselves from buying crap we don’t need. Either way, it’s a win-win situation.
Plant Nutrition Basics
Plants don’t need dirt, aka soil, to grow. They need something to support their root system, sunlight (or grow lights), water, and nutrients. Water, light, and nutrients are absorbed to do the photosynthesis thing that makes the chlorophyll thing that makes the plants grow and produce the munchy parts.
Each part of that is important, but right now we’re focusing on the nutrients part. Let’s start by going over the different nutrients plants need in order to grow up strong and healthy.
Macro & Micro Plant Nutrients
While as many as 60 different elements have been observed in different plants, only 16 are thought of as essential to their growth, development, and survival. These 16 essential elements, or nutrients, are broken down into macro and micro nutrients. As you might guess, macronutrients are needed in larger amounts, while micronutrients are trace elements needed in much smaller amounts.
The macronutrients are carbon (C), calcium (Ca), hydrogen (H), oxygen (O), sulfur (S), magnesium (Mg), nitrogen (N), phosphorus (P), and potassium (K). The needed volume of these nutrients changes as the plant moves through its life cycle.
The micronutrients are copper (Cu), manganese (Mn), iron (Fe), zinc (Zn), boron (B), molybdenum (Mo), and chlorine (Cl). Micronutrients, or trace elements, are used in very small amounts. Unlike macronutrients, plants use the same amount of micronutrients through their entire life cycle.
Why does that stuff matter? Well, it’s important to take note of the fact that your plant requires different levels of each macronutrient as it develops and matures. This is especially true for plants that flower or fruit. Unless you’re mixing up your own nutrient salts, you’ll want to select a good nutrient kit with easy-to-follow dosing instructions that cover the full lifecycle of your plants.
Pre-Mixed Nutrient Concentrates
For most hobbyist gardeners, pre-mixed nutrients make the most sense. They are easy to use, and take the guesswork out of determining the best formulations for each type of plant you plan to grow.
Most premixed hydroponic nutrient systems, or “kits”, come in 3 or more different bottles. Why? Because in most cases, nutrient salts don’t play well with other nutrient salts, and will result in a nutrient “lockout” if they are all combined together at once. This renders the nutrients useless, and a plant will not be able to absorb them. Manufacturers of hydroponic nutrients, bottle nutrients that play well with each other into the same container.
As a hydroponic gardener, you then apply the proper dosage from each bottle into the nutrient reservoir. Mix the dose from each bottle into the water in the reservoir thoroughly before moving on to the next bottle. Doing this helps make sure all those tasty nutrients are available to grow tasty plants.
My Favorite 3 Part Nutrient System
I almost always use a 3 part hydroponic nutrient system from General Hydroponics. The system is their Flora Series and it consists of FloraGro, FloraMicro, and FloraBloom. If you’re planning to only grow leafy green plants, you can drop FloraBloom and go with FloraGro and FloraMicro, but there’s a better-suited option for you below.
The Flora Series takes the guesswork out of nutrient formulation as your plants develop and shift through the stages of vegetation, flowering, and fruiting. Beyond the ease, it has been a very “clean” nutrient system and has made hydroponic system maintenance really simple compared to some other products I’ve tested.
One important thing to note: The mixing ratios General Hydroponics recommends are pretty strong. Start by cutting the recommended ratio in half, and use an EC meter to work your way up to the strength best suited for your plants. If your nutrient mix is too strong, add water to the nutrient reservoir to dilute it.
Single Part Nutrient System
A single part nutrient system is ideal if you’re growing leafy greens. Mix a single product into the nutrient reservoir, balance the pH, and you’re ready to grow. It doesn’t get any easier than that!
My top recommendation for a single part nutrient system is FloraNova Grow by General Hydroponics. They use some super-smart technology to suspend nutrient salts in the container in a way that keeps them from interacting until they’re mixed in the nutrient reservoir. Single part system, no nutrient lockout, SCORE!
I must confess, the FloraNova system is actually a two part system, BUT each part can be used independently of the other. FloraNova Grow is for the vegetative phase, but is also perfect for the entire lifecycle of leafy green plants. FloraNova Bloom is used during the flowering/fruiting phases of plant life, and it too is used by itself.
If you’re looking for the ultimate in simplicity, FloraNova is a pretty clear winner. Also, look around on Amazon for FlorNova Grow. There are better prices than the link above, but I wasn’t able to link to them.
The supplemental nutrient market is out of control. There is so much to choose from, and most of it is junk, at least for hydroponic gardeners growing normal fruits and vegetables. The four supplements listed below are what I rely on for great all-around results. If you’re focused on leafy greens there are only two ya need to be on the lookout for.
For Leafy Greens: Calcium/Magnesium, and rooting supplement
For Flowering/Fruiting Plants: Calcium/Magnesium, rooting, growth enhancer, and sweetening supplements
In my experience, if a plant is showing problems that are not related to temperature, light, or airflow, the symptoms are often related to a calcium and/or magnesium deficiency. Luckily it’s really easy to treat and prevent calcium and magnesium deficiencies.
My favorite supplemental nutrient is CALiMAGic from General Hydroponics. It provides a supplemental dose of calcium and magnesium, and it works wonders. This product has saved some seriously “tip burned” plants for me. Now, instead of waiting for problems, I use it as a preventive supplement and my plants love it!
Root development is important, especially with fruiting plants. As the plant puts on fruit, it needs a strong and healthy root system to support it and provide it with a constant supply of nutrients.
Botanicare Hydroguard is an amazing root inocculant that will introduce bacillus bacteria, a beneficial bacteria, into your hydroponic system. The bacillus bacteria will quickly colonize the rhizosphere and begin enhancing root systems while also aiding in the breakdown of organic material in the hydroponic system. Not only will this product enhance root systems, it will also help fight bad bacteria, and increase nutrient availability and absorption.
This product is also a must-have if you’re dealing with root rot. In many cases, root rot can be cleared up within a matter of days after introducing this product into your hydroponic system. If you’re growing plants, you need this stuff!
Growth enhancing supplements are great for bulking up plants, but I only use them for fruiting plants. Not only do they help bulk the plant, growth enhancers also help improve the overall yield produced by the plant due to increased size and flower production.
Sweeteners are a nice supplemental add-on if you’re growing fruiting plants. These supplements will help add that extra pop of sweetness to deliver over-the-top great fruits and vegetables.
Beyond these supplements, I wouldn’t buy anything else unless your plants start showing signs of specific deficiencies. The next section can help you identify specific nutrient deficiencies based on the signs and symptoms your plant is displaying.
Nutrient Deficiency Symptoms
If you’re ready to nerd out on nutrients, this is your section. Below you can see what role each nutrient plays, plus what symptoms relate to specific nutrient deficiencies. If your plants are showing signs of a problem, use this guide to troubleshoot them.
Nitrogen plays a big role in the early, vegetative development of plants. It is also associated closely with the overall yield of a plant.
Common nitrogen deficiency symptoms:
- Yellowing leaves/foliage. The “sciencey” term for this is chlorosis, and it indicates a plant is not producing enough chlorophyll (the stuff that makes the green color in leaves).
- Leaf firing. Browning at the tips and margins of the leaf form an arrow-like shape pointing toward the stem of the plant. Not the same as “tip-burn”.
- Slow or stunted plants.
Phosphorus is another early-stage all-star, especially for healthy root development.
Common phosphorus deficiency symptoms:
- Small leaves, thin stems, and slow overall growth.
- Some plants may exhibit purple foliage coloration.
- Slow maturity and less than stellar fruit production.
- Dark green overall color with dying leaf tips. Still not “tip-burn”.
Potassium, absorbed as potassium ions, is a transporter nutrient. Basically it moves sugar around and helps the plant form starch.
Common potassium deficiency symptoms:
- You guessed it, slow plant growth.
- Leaves that curl forward.
- Weak plant stalks.
- Mature/older leaves may exhibit “firing” around the edges of the leaf.
Calcium plays a vital role in the development of the cellular structure of plants.
Common calcium deficiency symptoms:
- Darker than normal green leaves.
- New leaves are malformed. The base of leaves appears normal, with constricted leaf tips. Leaf tips will often split since the tip of the leaf is not growing at the same rate as the rest of the leaf.
- Necrosis of leaf tips. Appears yellow at first, then turns brown/black as the cellular structure dies. This is what’s commonly called “tip-burn”.
- Early loss of flower blossoms
- Necrosis of root tips. You’ll normally notice this as black spots on the roots.
Magnesium is a required element for photosynthesis.
Common magnesium deficiency symptoms:
- The edges of leaves begin to curl up.
- Leaves begin to wither.
- Mature leaves begin to yellow.
Iron plays an active role in photosynthesis, nitrogen-fixing, and plant respiration.
Common iron deficiency symptoms:
- Young leaves will turn yellow between the veins of the leaf.
- If the lack of iron is severe enough, full portions of the plant may die off.
Sulfur can be absorbed from the nutrient solution, and also from the air. It helps form amino acids and is vital for protein/amino acid synthesis. Since it performs a function similar to nitrogen, it also has similar deficiency symptoms. The only difference is that sulfur deficiencies appear in new leaves.
Common sulfur deficiency symptoms:
- Underdeveloped, thin plants.
- Stunted growth, smaller than normal leaves, limited stalk/base development.
- Young leaves are yellow-green, yellow, or light green.
Boron helps plants metabolize carbohydrates.
Common boron deficiency symptoms:
- Limited flowering.
- New leaves are thick and curled up/down.
- Root tips dying back.
Manganese helps iron in the production of chlorophyll, and in the production of oxygen from water as part of the photosynthesis process.
Common manganese deficiency symptoms:
- Browning of leaves, leaves begin dropping off the plant.
- Early on, the area between the veins will begin to yellow close to the tip of the leaf.
Molybdenum enables plants to use nitrogen. Without it, plants cannot form amino acids.
Common molybdenum deficiency symptoms:
- Slow growth.
- Leaves begin to cup and/or roll into a spiral. Note: This rolling could also be due to excessive light levels. Look for multiple symptoms if you suspect a molybdenum deficiency.
- Older leaves start to yellow first, followed by younger leaves.
Copper helps in the production of vitamin A in plants, as well as in the formation of several other enzymes. Copper deficiencies are also tied to protein production problems.
Common copper deficiency symptoms:
- Leaves and stems have odd pigment
- Wilting/dying leaf tips
- Slow or stunted overall growth
Maintaining nutrient solution pH levels is important. Water quality is also very important.
Dissolved minerals and elements in municipal and well water can have a serious impact on the availability of nutrients in your nutrient solution. If your water has a ppm of more than 200, you could have problems with nutrient uptake. This is especially true if there are large amounts of calcium or magnesium in the water supply.
I've been using this kit for about 8 months and love it. It comes with everything you need to keep the tester calibrated and highly accurate.
The goal is to have water with a ppm close to zero. The lower the initial ppm, the higher the availability of the nutrients you add to the water. Another way to look at this is high ppm water steals money from you by reducing the usefulness of the nutrients you spent that hard-earned cash on.
If your water has a high ppm, it may be a good idea to consider installing a reverse osmosis system, or you could opt for a steam distiller. One thing to keep in mind is that reverse osmosis normally does a better job of lowering total TDS and PPM. There are some reasonably inexpensive RO systems on Amazon that work great for small to medium hobby gardens.
If you’ve never used a reverse osmosis or distillation system before, they are slow. You’ll need to plan ahead and be preparing water for your nutrient solution in advance. Since I have well water, I actually use both systems for different things around the house. Three distillers run daily to produce clean drinking water, and the RO system runs to create low ppm water for hydroponic systems.
Both systems produce wastewater, but they do so in different ways. A steam distiller produces waste in the form of steam, so there is no need to have a drain line. Reverse osmosis systems produce actual wastewater that requires a drain line. This is something to keep in mind when considering these systems.
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