With it’s rather fantastical, comic book-sounding name, you could be mistaken for thinking that vermiculite weakens the powers of super heroes, or exists as some kind of potent extraterrestrial mineral that was delivered to earth via asteroid from the depths of space. The reality isn’t quite as exciting as this, but vermiculite is incredibly useful and should certainly have a place in a gardener’s arsenal.
What is it?
Put simply, vermiculite is a mineral that can be used to insulate and retain moisture. At garden centres it is usually sold in rather gargantuan bags that are several litres in volume. For the urban gardener who is likely to a) not have enough space to store a sack-full of the stuff and b) will never get through a sack-full of the stuff, this isn’t ideal. However, if you look carefully you may be able to locate smaller, more humble packages of the mineral – the one pictured above was lurking in a dusty corner of my local garden centre, and cost me something in the region of £1.
Use it for seedlings and cuttings
The first time I used vermiculite, I was growing basil from seed. Following the instructions on the seed packet, I sprinkled a layer of the glistening, sandy substance on top of the soil, and waited for the little green shoots to appear. A quick phone call to my dad clarified what the stuff was actually for – it retains moisture and heat, helps to stop mould settling on the surface, and is very light, making it easy for little shoots to break through.
For some seedlings and cuttings it’s also a good idea to mix vermiculite in with the soil, particularly for cuttings. This is because of its moisture-retaining properties and the fact that it gives young roots something to take hold of, whilst also aerating the soil.