The black stuff is called Picón, although we’ll lose the accent now, as people probably won’t search for the information with it! Picon is volcanic ash from the eruptions here in the 18th and 19th centuries. You’ll find it everywhere around volcanoes here. Most commonly, it’s black, but you can get a red version from areas like Montaña Roja in Playa Blanca.
Why is Picon used when growing stuff?
Putting a layer of picón on the soil when planting has several benefits:
It prevents soil erosion
With our incredibly dry climate and steady breezes, soil very quickly turns to dust here, and is then blown away! The weight of the picon prevents this happening.
It acts as a weed barrier
A healthy layer of picon stops weeds poking through, and makes it easy to spot and pull them out before they get established.
It helps keep moisture in the soil
Simply having a layer on top of the soil reduces it’s direct exposure to the sun, so prevents it from drying out.
It absorbs moisture from the air
This is the really clever part! As the tiny stones warm during the day and cool at night, they draw in what little moisture there is in the air, filtering down to the plant and soil underneath.
You’ll see picon everywhere on the island where things are being grown. It’s a very clever adaptation of a naturally occurring substance that has meant we can grow so much here, despite having only 150MM of rain a year – comparable with the nearby Sahara Desert.
It was formed during the time of the volcanic eruptions and covers many of the mountains on the island. In approved areas, it can be “mined” from the mountain, and then simply passed through graders that give it a uniform size.
Picon can be bought in bags from garden centres like Flower Power, or by the lorry load.