What You Need to Know About Hydroponic Nutrients and Fertilizer

Hydroponic gardening is done without soil, no dirt. All soil naturally contains essential plant nutrients . Commercial fertilizers don’t contain all the nutrients required as they are attained form the soil.

Hydroponic plants use no soil, so naturally there are no soil borne nutrients. Hydroponic Nutrients are needed . Hydroponic Nutrients are fertilizers formulated specifically for Hydroponic systems, these Hydroponic Nutrients contain the essential elements that in nature would be in the soil, but they are soluble.

Various plants require different proportions of Hydroponic nutrients at different times in their growth cycles. Many Hydroponic nutrients are labeled as ‘grow’ or ‘bloom’ so that even a new grower will recognize these solutions easily. Rotating your Hydroponic nutrients in accordance with plants growing cycle is an important factor.

The depletion of certain nutrient elements during various stages of the plants growth can be overcome if this is done properly. Ideally you should change the solution periodically, although multiple variables can influence this. The nutrient solution to water ratio must however remain consistent. Fertilizer levels will increase with excessive evaporation and can cause extensive damage.

Stages of Plant Development

If starting your plants from seed within the Hydroponic system, that is – not transplanting seedlings from a conventional growth method, then germination is one of the stages you must deal with. Seeds store nutrients and will use up these nutrients before seeking external sources. The stored nutrients are all the that the seed needs to germinate and get started. They don’t need any nutrients added to the water at this point. In fact adding too much nutrients at this point has the potential of doing more harm than good.

Early Growth

Soon after Germination, when the plants are basically sprouts is the Early Growth stage. During this phase plants mature from a small sprout or seedling to Adult Size. The growth rate naturally varies from plant to plant . Keep in mind that in a properly cared for Hydroponic system plants grow an average of 25% faster than they would in soil.

Small amounts of nutrients be added once the plants have begun grow a little, roughly 1/8 strength till true leaves appear. Young plants are tender and fragile so adding too much can easily burn them up. After the plants show two or more sets of true leaves increase to 1/4 strength. If you notice that the leaf tipsshow any signs of browning, burn up or curling, cut back on the nutrients and add some pure water till they mature a tad further.


Maturation is the third stage of plant development. Generally the growth rate will taper off considerably and the plant adopts the identifiable characteristics of a mature specimen of its species. Flowering plants will form the flowers that are characteristic of its cultivar. The development of fruits and vegetables occurs during this stage.

Your solution should be drained near the start of this stage of plant development and a new recharged solution added.

The new solution should be Slightly more than Full Strength – but you must be starting with a fresh solution and water. Don’t reuse the old solution it has an abundance of useless elements in it at this point.

Leafy plants, spinach, lettuce … should receive larger amounts of Nitrogen to aid in the development of the leaves and foliage which is what you will be harvesting.  Fruit and vegetable baring plants tomatoes, eggplant will need less nitrogen but more of other nutrients and trace elements.


Hydroponically grown plants are generally easier to harvest than those grown by conventional methods. In most cases, they are elevated, and they are usually grown indoors. For several days prior to harvest, the plants should be flushed with plain water to clear out salts and mineral deposits.

Leafy green plants, such as spinach and lettuce should grow to the point where they are almost ready to develop flower stalks, This is when they should be harvested. Do not allow them to “bolt” to seed, at this point the crops is wasted and will have a nasty taste. Fruits and vegetables need an abundance of hydroponic nutrients at this point, as well as liquid. However care should be taken with plants that are being grown for their foliage – lettuce, spinach, cabbage – as elevated nutrients too close to harvest can lead to a bitter tasting leaf.

Nutrients should cease at this point.

Hydroponic nutrient solutions are generally sold in a concentrated form. The grower must mix it according to manufacturers instructions and as per the requirement of the subject plant. For instance a weaker solution should be used for plants in poor growing conditions such as overheated gardens, low or poor lighting or just crowded plants. Newly planted cuttings will also initially benefit from a weaker solution.

Normally growing and spaced healthy plants need a basic “normal” or regular solution . If your garden can handle high volume growth, has good lighting and ventilation and carbon dioxide production & circulation, you could probably use a stronger Hydroponic nutrients solution. It is advisable to experiment on a few plants first rather than burning out an entire crop.  Increasing the fertilizer concentration gradually will also reduce the chances of the plant burning up.

A. Temperature of Solution.- The Nutrient solution should be kept between 65 degrees minimum and 75 degrees maximum. A hot solution will breed Algae, bacteria and fungi as well cooking tender roots. A cold solution can shock and kill the plants at worst, at the least it will retard development.

B. Checking pH.-After adding the nutrients, wait at least an hour prior to checking pH. Optimum pH range is 5.5-6.0 for most plants – although it does vary somewhat. See: pH in Hydroponics

C. Aeration.  You should aerate the solution continuously to oxygenate the roots, maintain hydroponic nutrients and discourage anaerobic bacteria . An inexpensive aquarium pump, and stone filter in the reservoir will suffice – the same setup that is used in many aquariums.

D. Chlorinated Water.  if you are using Chlorinated tap water in your hydroponic set up, it should be allowed to sit for 48-72 hours in order to dissipate the chlorine.

Basically conductivity {EC} measures the nutrients in the solution. Low conductivity indicates a low nutrient concentration and high EC – a high concentration.

Conductivity is an indication of the nutrient solutions strength . A higher conductivity has more dissolved solids in the solution. If the conductivity is too high plants can experience fertilizer burn. As the plants mature, a stronger nutrient solution is needed, so conductivity is increased by adding concentrated nutrient, which increases the PPM and theoretically the nutrient value. Various plants need differing nutrient strengths.

There are multiple theories and complex formulas many hydro-enthusiasts use, and the jargon is sometimes confusing, and befuddles new comers. To simplify matters , let me state that you really don’t need all the expensive and befuddling equipment and formulas hydroponic supply houses will try and sell you. You really don’t need  EC PPM, or TDS Meters to successfully grow plants hydroponically.

Any nutrient solution is composed of multiple mineral elements, none of the meters available  can gauge which elements are in your nutrient solution. There are no meters that will indicate what elements are in your solution, or in what quantity . They can’t even tell you if the elements within the parts per Million are useful or harmful elements to your plant. For a nutrient solution to do it’s intended job , all the mineral elements within it need to be in balance.

Plants will absorb primarily the elements within the solution that they need, leaving the rest behind. Over time this creates a more and more unbalanced solution. As time progresses , any mineral elements the plants use become depleted in increasingly larger quantities, useless as well as harmful mineral elements wind up comprising the bulk of the ‘Parts’ in your Part Per Million {PPM} formula. You eventually wind up with toxic levels of some elements, and a deficiency of useful ones.  A heavy concentration of one element can create a detrimental chemical reaction restricting or blocking another element and interfering with a biological function. Excessive nutrients can also cause “nutrient lockout” , brown leaves, curling, etc .

Nutrient Deficiencies

Plants need 16 elements to flourish. [Some say 18.]

1.Nitrogen (N) Encourages leaf growth. Excessive leaf growth discourages blossoms and fruit. So high Nitrogen nutrients should be used on spinach and lettuce but not tomatoes or eggplant.

2. Potassium (K) is Good for flowering and fruit development. It also encourages flowering, and therefore fruiting.

3. Phosphorous (P) helps produce healthier seeds and strengthens the plants root structure. It is necessary for photosynthesis and respiration, cell division and energy transport.

4. Calcium (Ca) is an essential plant nutrient, it is necessary for cell formation, it forms calcium pectate which helps bind cells to one another and strengthens the cell walls of plants.

5. Magnesium (Mg) is the central element of the chlorophyll molecule and is essential for photosynthesis, as well as Sugar synthesis. It facilitates the plants uptake of Nitrogen, sulfur and phosphorous. Magnesium is also needed for the plants seed production towards the end of its life cycle and for germination in its early stage.

6. Iron (Fe)

7. Sulphur (S)

8. Manganese (Mn)

9. Copper (Cu)

10. Zinc (Zn)

11. Molydenum (Mo)

12. Boron (B)

13. Chlorine (Cl)

14. Carbon

15. Hydrogen

16. Oxygen

Other trace elements such as silica / silicon are at times advantageous as well. See: Hydroponic Silicon

You need to start with the correct nutrient for the Plant you are growing, add nutrient solution as you go along and flush the solution out and start over again with fresh water periodically. Multiple variables determine how frequently you should flush. See: Hydroponic Flushing

Should you decide to change the nutrient solution based on EC/TDS/PPM readings. You can adjust the readings by either diluting it with more water or by adding more nutrients to raise the numbers to a desired level. This will keep the nutrient solution with a specified range indefinitely, not necessarily a desirable one, but at least your numbers will look good – maybe your plants too.

Environmental conditions will also affect how plants perform, and how well they absorb the needed nutrients. Temperature, Light, Humidity … See: Maintain Solutions

Over Fertilizing ~Over-Nute

Over Fertilizing can cause the leaf tips to brown and curl upwards. Under Fertilizing causes the leaf tips to curl downward, this is my personal observation – not a scientific fact, I have heard people claim that over fertilizing cause tips to curl down, not up. So, in any event the leaf tips will curl and generally the tips turn brown, much like a burn, as an early symptom of over fertilizing.

if over-fertlizing is a problem, flush the reservoir with a milder nutrient concentration.

If your having a deficiency issue, you need to do the same flush – but first diagnose what the deficiency is. if the symptoms appear on new leaves, its usually micro nutrients, On old leaves it’s probably major nutrients. Check the nutrient solution you are using to be certain they contain a complete menu.

One quagmire I encountered when I first starting gardening hydroponically was reading and believing that plants will only take up the nutrients they need and leave the rest behind. The natural assumption with this is that if they are only absorbing what they need – then how can they absorb too much of an element ?

Technically – the plant can’t be over-fertilized due to absorbing excessive quantities of any particular nutrient. What does occur however, is that over-fertilizing causes damage on a cellular level. In heavy concentrations, nutrients can and do inhibit the plants ability to perform mitosis and photosynthesis . A heavy concentration of a particular element creates a detrimental chemical reaction restricting or blocking another element and interfering with a biological function. Excessive nutrients can also cause “nutrient lockout” , brown leaves, curling, etc .