Gardening: Passive hydroponics

Introduction

So I've been experimenting with some passive hydroponics this year on my balcony.

I'm very lazy so I don't like to check up on the garden too often. I also want to be able to leave the house for extended periods of time without having to worry about watering the plants.

• Passive in this context means that absolutely no electricity is required

• The plants grow in sunlight and there are no pumps to circulate water

I'm happy to report that the experiment has been a success: we've enjoyed a steady supply of spearmint, basil and cucumbers for a while.

Minimal effort is required beyond harvesting and planting. Depending on the size of the bucket and the plant, the interval for 'irrigation' can be anything from 2 weeks to 2 months.

Getting started

Passive hydroponics is stupidly simple: you stick the plant to a pot of water with some nutrients and you're done.

What's required:

• water
• light
• a bucket
• 'scaffolding' to hold the plant in place
• nutrient solution (plant food that you mix in with the water)

These can be easily sourced from almost any modern garden/hardware store.

There is of course a lot more to this, but in practice it's really that simple.

One very important complex thing to consider is the pH of the water, denoting 'potential of hydrogen', that is the scale used to specify the acidity of an aqueous solution.

So you need the water to be with a pH around 5.4 to 6.0 for the plants to be able to 'feed'.

Many of the ready-to-use hydroponic nutrients solutions available are designed for tap water with a high pH (8.0 ... 8.5) and will drop it to the correct levels.

Good luck!

History: The Hanging Gardens of Babylon

Hydroculture is positively ancient and different techniques have been employed for thousands of years.

• One of the Seven Wonders of the Ancient World, the Hanging Gardens were built on top of ziggurats and plants were irrigated on channels

• A Chinampa is a type of Mesoamerican agriculture to grow crops on shallow lake beds

• The 13th century Chinese agricultural manual Wang Zhen's Book on Farming (王禎農書) described floating wooden rafts which were piled with mud and dirt and which were used for growing rice, wild rice

• 1627: the earliest published work on growing terrestrial plants without soil was the Sylva Sylvarum or 'A Natural History' by Francis Bacon

• 1699: John Woodward published his water culture experiments with spearmint. He found that plants in less-pure water sources grew better than plants in distilled water

• 1842: a list of nine elements believed to be essential for plant growth had been compiled, and the discoveries of German botanists Julius von Sachs and Wilhelm Knop, in the years 1859–1875, resulted in a development of the technique of soilless cultivation

Further resources

https://en.wikipedia.org/wiki/Hydroponics

https://en.wikipedia.org/wiki/Passive_hydroponics

Kratky, B.A. (2009). "Three Non-Circulating Hydroponic Methods for Growing Lettuce". Acta Horticulturae (843): 65–72. doi:10.17660/actahortic.2009.843.6. ISSN 0567-7572.

https://www.ctahr.hawaii.edu/hawaii/downloads/Three_Non-circulating_Hydroponic_Methods_for_Growing_lettuce.pdf

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