From a US “interested reader”. Is the ancient history of hydroponics true or not?
I have a strong interest in hobby hydroponics and read quite a lot. My current interest is particularly the history of hydroponics. A fan of your column told me you don’t believe that the commonly quoted examples of the ‘hanging gardens of Babylon’ and the ‘Aztec floating gardens’ were actually hydroponic. Is this so, and why not?
Most of the many general books on hydroponics contain a chapter, or at least a segment, on the history of hydroponics. It is also very common in the articles picked up by an internet search. An almost universal thread is to quote the two examples you mention. Quite often the wording is identical – not unusual for the internet!
I did write about both of these in detail seven years ago, because I found them to be very interesting topics, but here I’ll just give a brief summary.
Definition of hydroponics
When getting down to the basics of whether they were hydroponic, we need to start with a definition.
I consider ‘hydroponics’ to be synonymous with ‘soilless culture’. I define both as: a system for growing plants isolated from the soil, with or without a medium, in which all the water and nutritional needs of the plants are supplied by a nutrient solution.’
The hanging gardens of Babylon
These came to prominence, and have remained so, because they were listed as one of the seven wonders of the ancient world, however, there is some doubt that they even existed.
Babylon was some 90km from modern Bagdad and in the sixth century BC was probably the largest city of the known world. The most common story is that the hanging gardens were built by Nebuchadnezzar (of bible fame) for his queen, Amyitis. Her homeland was green and mountainous, in contrast to the flat, sun-baked landscape around Babylon, so the king decided to make her feel more at home by building a small mountain with rooftop gardens.
A typical description was that given by Diodorus Siculus: “The Garden sloped like a hillside and … rose from one another tier on tier… On all this, the earth had been piled… and was thickly planted with trees of every kind… The water machines [raised] the water in great abundance from the river, although no one outside could see it.”
These water machines were operated by slaves. This was possibly some form of endless bucket chain, although an Archimedes screw has also been suggested, but this was invented three centuries later.
Why the uncertainty about the existence of the hanging gardens? Several points: The Babylonians had an extensive written history, but there is no mention of them. The stories were written in Greece several centuries later and all from second hand quotes, by authors known to be flexible with the truth.
Were they strictly hydroponic?
Of course not, they would have used irrigated soil. However, they probably used soil in independent containers and relatively sophisticated irrigation techniques, which indicate to me that this is an admirable predecessor of hydroponics.
Aztec floating gardens
There is no doubt the chinampas existed, because remnants are still there today, as the World Heritage area of Xochimilco, part of Mexico City. However, although universally referred to as the ‘floating’ gardens, they don’t float, and never have.
Chinampas are long, narrow rectangular beds built in shallow water and surrounded on three or four sides by canals. Marked out on a firm base with strong reeds, layers of mud and aquatic plants were then piled up to give a compost bed covered with a layer of mud. The mud was mainly scooped from each side of the chinampa to make the canals. To prevent erosion, the sides were retained by stakes and woven reeds and stabilised further by growing trees, such as willows, at regular intervals along the sides.
Their size varied, typically about 100 square metres (1000 square feet), but could be 10 times this. Their height was about half to one metre (two to four feet) above the water level, which gave the bed a very high water table.
This area is surrounded by high mountains, which drained into a set of five shallow landlocked lakes, which were salty. Starting from the ninth century, in order to extend the limited fertile land, chinampas were built around the fresh water inlets. The area peaked at about 20,000 hectares (50,000 acres) under the Aztecs at the time of the Spanish conquest. This expansion required the building of extended dam walls to separate fresh from salty water. The Spaniards demolished these dam walls to provide building materials for their new city, thus unintentionally setting in chain the decline of the chinampas.
Are the chinampas hydroponic? Definitely not—they are soil-based. However, even today they are an excellent form of intensive agriculture. In the sixteenth century, they were spectacularly more advanced in both technology and scale than anything in the western world.
This is an example of how myths can be illogically advanced. It is understandable how many articles describe the chinampas as rafts with roots growing down into the water. However, to describe and draw these “rafts” being “poled by the gardener to the market place,” is ridiculous! Even if they had floated, their size and weight would have needed a small army to move just one (not to mention the traffic congestion in narrow canals!). Ω
October 2013 / Issue 136