# Hydroponics

> Growing plants with their roots in a nutrient solution

- Date: 1860
- Era: Industrial age
- Domain: [Agriculture & Livestock](https://lastcodex.org/en/domains/agriculture/)
- Rebuild stage: IV (Science & industry)
- Difficulty: 2/5
- URL: https://lastcodex.org/en/inventions/hydroponics/

Hydroponics grows plants without soil, with their roots in water that carries the mineral nutrients they need. The solution does the work of the soil, while the roots are kept in the dark and given air. In 1860 the botanist Julius Sachs published experiments in which plants grew to seed in such solutions, and in 1937 William Gericke gave the method its name.

![Hydroponics · Growing plants with their roots in a nutrient solution](https://lastcodex.org/_astro/plate.CRsJ6fj2_tsWfS.webp)

## Legend

1. Young maize plant
2. Pierced cork holding the stem
3. Dark paper keeping out the light
4. Roots
5. Nutrient solution

## What it is

Hydroponics is the growing of plants without soil, with their roots in water. A solution of mineral salts brings them what soil would: water and the chemical elements that plants take from the ground. The leaves still need light and the carbon dioxide of the air, as in a field. In a related method, aggregate culture, the roots grow in sand, gravel or another material that holds no food of its own, and the solution is poured or pumped through it.

Plants are made mostly of carbon, hydrogen and oxygen, which come from the air and from water. The rest, in much smaller amounts, comes from the soil: nitrogen, phosphorus, potassium, sulphur, calcium and magnesium, and in traces iron, chlorine, boron, manganese, zinc, copper, nickel and molybdenum. Each of them is indispensable, and a plant short of any one grows badly, even when it has all the others. A nutrient solution is a recipe that supplies all of them, dissolved in the right proportions. Some of these trace elements were recognised as essential only through experiments in nutrient solutions, where nothing reaches the plant except what the grower puts in.

## How it works

The solution replaces the soil but not everything around the roots. Roots breathe: they need oxygen, which they find in the air spaces of a good soil. In still water they soon run short of it. Growers bubble air through the solution, or leave a layer of air between the solution and the support of the plant, where part of the roots can hang. The root zone is also kept dark: early experimenters wrapped their jars in paper, and growers cover their tanks.

![A long shallow tank on trestles, covered with wire netting and a bed of straw from which tall staked tomato plants grow, the bed lifted at one end to show roots reaching down into the solution](https://lastcodex.org/_astro/v3.C70NLpDX_Zw5Wcz.webp)
_A tank of the 1930s: the plants stand in a porous bed laid over the nutrient solution._

The plant is held at the neck by a cork, a perforated cover or a small pot, and its roots hang directly in the solution. Large plants such as tomatoes need support for the stem, and potatoes a bed in which their tubers can form.

The grower keeps the solution within limits. As the plant takes up water and salts, the solution changes: it grows stronger or weaker, and more acid or more alkaline. Too much fertiliser injures the roots, and too little starves the plant. Commercial growers measure the solution and correct it; a simple home system starts with a complete solution at the right strength and replaces it for the next crop.

## How to do it

![A wide glass jar half wrapped in dark paper, a young lettuce in a small black mesh pot set in its lid, the white roots hanging into the solution below a layer of air](https://lastcodex.org/_astro/v2.BnmFXI_m_Z16xjWO.webp)
_In the jar, the solution level drops as the lettuce drinks, leaving a moist air space where the upper roots breathe._

This jar grows one lettuce without a pump, by the non-circulating method that the horticulturist Bernard Kratky described in Hawai‘i. You need a clean glass jar with a wide mouth and a lid, a small mesh pot that fits a hole in the lid, a plug or cube of growing medium such as coconut fibre or rock wool, a lettuce or basil seedling, and a complete fertiliser sold for hydroponics, with trace elements.

Wrap the jar in dark paper or aluminium foil, leaving a narrow slit to see the level. Cut a hole in the lid so that the mesh pot sits in it by its rim. Mix the fertiliser with clean water exactly as its label says, and fill the jar until the solution just touches the bottom of the pot. Set the seedling, with its plug, in the pot, and place the jar in a bright window or under a lamp.

Do not top up the jar to the brim. As the lettuce grows, it drinks the solution, the level falls and a layer of moist air opens under the lid. The roots that hang in it take their oxygen from the air, and those below go on taking up water and food. If the level drops too far before the lettuce is ready, add a little solution, only enough to wet the lowest roots: filling it up again would drown the roots that now live in the air. Harvest the leaves before the solution runs out.

Fertiliser salts are chemicals. Keep the packet closed, labelled and out of reach of children and pets, measure them with spoons kept for that use, wash your hands after handling them, and never drink the solution. Handle the glass jar with care. If you add an air pump or a lamp, keep the plugs and wiring above and away from the water. Wash the leaves before eating them, and pour the spent solution, diluted, on garden soil rather than into a pond.

## History and evolution

![Three small glass phials of water on a wooden table, each holding a rooted sprig of spearmint, the water clearer in one than in the others](https://lastcodex.org/_astro/v1.Byh_THC0_1DPvng.webp)
_In 1699 Woodward compared spearmint grown in different kinds of water._

In 1699 the English naturalist John Woodward grew sprigs of spearmint in phials of rain water, river water and water from a conduit, in one case with garden soil added. The plants gained most weight in the muddiest water, and he concluded that plants are made of earth rather than of water. He was looking for what plants are made of, and gave them no defined food.

The method grew out of the chemistry of plant nutrition in the middle of the nineteenth century, once chemists understood that the soil supplies plants with certain elements as well as water. Some of them, such as Jean-Baptiste Boussingault in France, already grew plants in sand and other inert materials to study their nutrition. The next step was to do without any solid medium. In 1860 the German botanist Julius Sachs published experiments in which land plants grew in watery solutions of known salts and produced seed that could germinate. He raised the seedlings in sawdust, fixed each in a pierced cork in the neck of a [glass](/en/inventions/glass/) jar, and let the roots hang in the solution. Jars of this kind, wrapped in paper to keep out the light, were still recommended for school demonstrations in the twentieth century.

For decades water culture was a laboratory tool for studying what plants need, and it led to the discovery of several trace elements. Dennis Hoagland, at the University of California, published a study of the best nutrient solutions for plants. In the 1930s his colleague William Gericke adapted the method to growing crops such as tomatoes and potatoes in large tanks, and named it hydroponics in an article in Science in 1937. The newspapers took it up, and Hoagland and Daniel Arnon warned that many claims made for it were exaggerated. In the 1960s the tower greenhouses of Othmar Ruthner carried their plants past a trough of nutrient solution, an early form of the [vertical greenhouse](/en/inventions/vertical-greenhouse/). Later, Bernard Kratky described a method with no pump and no electricity, in which the solution is added once and its level is left to fall.

## Key facts

- Plants grown to seed in a nutrient solution: Julius Sachs, 1860
- Name hydroponics in print: William F. Gericke, Science, 1937
- What the solution must supply: Water and the essential mineral elements
- What the roots also need: Air and darkness

## Requires

- [Glass](https://lastcodex.org/en/inventions/glass/): Melted sand you can see through (c. 2,500 BCE)

## Leads to

- [Vertical greenhouse](https://lastcodex.org/en/inventions/vertical-greenhouse/): A glass tower that carries its plants up and down on moving trays (1963)

## Sources

- [The Water-Culture Method for Growing Plants without Soil (Circular 347, revised 1950)](https://archive.org/details/watercultureme3450hoag), D. R. Hoagland, D. I. Arnon, California Agricultural Experiment Station
- [Hidroponía en “tiempos modernos” (II) (Horticultura Internacional 59, 2007, pp. 26–33)](https://www.mapa.gob.es/ministerio/pags/Biblioteca/Revistas/pdf_hortint/hortint_2007_59_26_33.pdf), C. R. Arano, Horticultura Internacional
- [Lectures on the Physiology of Plants (1887), passage on the water cultures of 1860](https://books.google.com/books?id=ZLvPAAAAMAAJ&pg=PA283), Julius von Sachs, Clarendon Press
- [Some thoughts and experiments concerning vegetation (Philosophical Transactions 21, 1699, pp. 193–227)](https://doi.org/10.1098/rstl.1699.0040), John Woodward, Royal Society
- [Hydroponics: Crop Production in Liquid Culture Media (Science 85, 1937, pp. 177–178)](https://doi.org/10.1126/science.85.2198.177), W. F. Gericke, Science
- [The Meaning of Hydroponics (Science 101, 1945, pp. 142–143)](https://doi.org/10.1126/science.101.2615.142), W. F. Gericke, Science
- [Optimum Nutrient Solutions for Plants (Science 52, 1920, pp. 562–564)](https://doi.org/10.1126/science.52.1354.562), D. R. Hoagland, Science
- [Apparatus for the artificial cultivation of plants, bacteria, and similar organisms (US 3,254,447, filed 1963)](https://patents.google.com/patent/US3254447A/en), Othmar Ruthner, United States Patent Office
- [Hochhäuser der anderen Art (9 May 2021)](https://www.tagblatt-wienerzeitung.at/nachrichten/reflexionen/geschichten/2103168-Hochhaeuser-der-anderen-Art.html), Christian Hlavac, Wiener Zeitung
- [A Capillary, Noncirculating Hydroponic Method for Leaf and Semi-head Lettuce (HortTechnology 3, 1993, pp. 206–207)](https://doi.org/10.21273/HORTTECH.3.2.206), B. A. Kratky, American Society for Horticultural Science
- [A Suspended Net-Pot, Non-Circulating Hydroponic Method for Commercial Production of Leafy, Romaine, and Semi-Head Lettuce (VC-1, 2010)](https://www.ctahr.hawaii.edu/oc/freepubs/pdf/VC-1.pdf), B. A. Kratky, University of Hawai‘i, College of Tropical Agriculture and Human Resources
- [Molybdenum as an Essential Element for Higher Plants (Plant Physiology 14, 1939, pp. 599–602)](https://doi.org/10.1104/pp.14.3.599), D. I. Arnon, P. R. Stout, Plant Physiology
- [Chlorine, a Micronutrient Element for Higher Plants (Plant Physiology 29, 1954, pp. 526–532)](https://doi.org/10.1104/pp.29.6.526), T. C. Broyer, A. B. Carlton, C. M. Johnson, P. R. Stout, Plant Physiology
- [Nickel: A Micronutrient Essential for Higher Plants (Plant Physiology 85, 1987, pp. 801–803)](https://doi.org/10.1104/pp.85.3.801), P. H. Brown, R. M. Welch, E. E. Cary, Plant Physiology
- [Hydroponics Systems and Principles of Plant Nutrition: Essential Nutrients, Function, Deficiency, and Excess](https://extension.psu.edu/hydroponics-systems-and-principles-of-plant-nutrition-essential-nutrients-function-deficiency-and-excess), Penn State Extension
- [Linking the key physiological functions of essential micronutrients to their deficiency symptoms in plants (New Phytologist 242, 2024, pp. 881–902)](https://doi.org/10.1111/nph.19645), G. H. Lilay, N. Thiébaut, D. du Mee et al., New Phytologist

Fact-checked on 2026-10-22.

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The Last Codex · https://lastcodex.org/en/inventions/hydroponics/ · © The Last Codex. Texts, plates and figures: CC BY-NC-ND 4.0.