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Perlite, Vermiculite, Peatmoss, and Coco Coir

Perlite

Perlite is derived from super-heating volcanic rock: heat is applied to expand (pop) volcanic glass in a furnace. It is a porous material which particles are lightweight, hard, roundish, and look like white granules that are crushable, i.e. not squishy. Perlite helps with aeration and drainage. The particles prevents soil compaction, and small holes in the particles create room for oxygen in your grow medium ‒oxygen is just as important to plants as sunlight, water and fertilizer. The small holes also improve drainage: that room created for oxygen also also prevents water damage, and mold. Perlite also helps to hold the moisture and nutrients. Perlite has slightly alkaline pH.

Have a gnat problem? Perlite is your friend! A thin layer at the surface can help keep bugs away. This trick can be especially helpful to keep houseplants healthy and free of unpleasant squatters.

Vermiculite

Vermiculite is obtained by super-heating mica. It is a spongy material which particles are lightweight, soft, plate-like, and dark brown to golden brown in colour. Vermiculite helps with moisture control and nutrient delivery: it provides ease of re-wetting and consistent release of humidity, while holding onto nutrients and helping to convey them consistently to the plant. Vermiculite also helps with aeration, including through preventing compaction. Vermiculite has close to neutral pH.

Do you sometime struggle to remember to water your houseplants? Vermiculite might be your saviour ‒and theirs! Next time you’re preparing soil for a moisture-loving plant, consider adding some to the mix.

Peatmoss

Peatmoss comes from sphagnum fibres that have partially decomposed in a bog. It is light and spongy and crumbles into small clumps. Peatmoss has a remarkable ability to hold water and to retain nutrients from leaching out of the soil. The finer the fiber, the more water-holding capacity it has; it can absorb up to 16-26 times its weight in water, but can be difficult to re-wet if left to dry out. Peatmoss is slightly acidic, so if you choose to use peatmoss, a pH ajuster such as lime should be added to the mix to balance out the acidity.

Peatmoss is a biodegradable material and will naturally decompose over time sending it's carbon content to the atmosphere. It doesn’t have a very long shelf life and after 1-2 years (from the time you purchase it), the fiber starts breaking down, making it ineffective at its primary job: to hold moisture. Expiration in this case doesn’t mean the peatmoss turned moldy or smelly (and it doesn’t as long as it’s been kept dry) ‒just that it loses its structure.

Usage of peatmoss should be kept to a minimum considering it's environmental impact, and some countries altogether ban it's usage in horticulture and horticultural products. Biochar is a great alternative to peatmoss.