Volcanic lapilli 3/5 mm - 2 litre pack

What it is and where it comes from

Lapilli are crushed lava rock, a natural inert material of volcanic origin rich in minerals and iron. The granules are porous, angular and reddish-brown in colour. This 2 litre pack is graded to 3/5 mm.

How it behaves in the pot

Water passes through at once. It is the first thing you notice when watering a pot containing volcanic lapilli: no waterlogging, the excess runs down and out of the drainage holes. The internal porosity of each granule, however, keeps the substrate from drying out, because it holds moisture and releases it slowly to the surrounding soil over the following hours.

Between the angular granules there are air pockets that roots colonise readily, with fine ramification and a compact root mass. The real advantage is another one: lapilli do not break down. Years go by between one repotting and the next and the granule is still the same, with none of that clayey sludge that clogs the pores and suffocates the root system.

Features

• Material: volcanic lapilli, natural inert
• Grain size: 3/5 mm
• Pack capacity: 2 litres
• Composition: rich in minerals and iron
• Function: drainage and water retention

Which grain size and for which plants

3/5 mm is the middle size, the one that suits most medium-sized growing and display pots. On shohin and shallow pots it looks coarse; on large specimens it can be used, though many prefer a larger grain in the body of the substrate and keep this one for the top layer.

It pairs well with akadama and pumice in conifer mixes, where drainage matters more than retention: pines, junipers, yews. It also works with broadleaves, lightening a substrate that on its own would stay too wet. The same grain is useful as a top dressing, where the dark colour finishes the pot neatly.

How to use it when repotting

First of all, sieve it: crushed lapilli always carry dust and fine flakes, which form an impermeable crust at the bottom of the pot. Sieve it dry, keep the grade and discard the rest. A thin layer of granules on the bottom, over the drainage mesh, gives you the filtering layer.

Among the roots the material should be settled with a chopstick, without tamping: the gaps close by themselves with the first watering. Water generously until the water runs clear from the holes, repeating two or three times. That washes away the last of the dust.

Frequently asked questions

Can volcanic lapilli be used on their own?

They can, but you need to know what that means. Being inert, they supply no nutrients and hold less water than a clay such as akadama: watering becomes more frequent and feeding is essential. Generally it is better to combine them with a more retentive component.

Do the granules crumble over the years?

No. Lava rock is hard and keeps its shape and porosity throughout the period between one repotting and the next, even through freeze and thaw. That is the main reason it is chosen: the substrate structure stays open and oxygenated instead of compacting.

How many plants will a 2 litre pack cover?

It depends on pot size and how much lapilli goes into the mix. This quantity is intended for a few repottings or to complete a mix: on medium-sized pots two litres are enough for one or two repottings, or for top dressing several plants. Leftover material keeps dry, does not deteriorate and can still be used the following year.

What is included

• Volcanic lapilli, grain size 3/5 mm
• 2 litre pack

If you prefer to measure out the components yourself, and many customers who buy in Italy do, you can put together your own blend on the made-to-measure soil page.