Vermiculite is a very handy substrate. Organic and natural. The perfect addition to a good potting mix, but also popular used by itself for hydroponic growing. This is for a 5 litre bag of Vermiculite. One bag measures about 35cm long x 16cm wide x 10cm deep. An easy size to store with your potting supplies.

What is vermiculite?

Vermiculite is magnesium-aluminum-iron silicate. It is an all-natural mineral product used as a substrate to help increase water retention and nutrient retention levels to look after our precious plants, especially babies, fast growers and moisture-lovers. Vermiculite is non-toxic and harmless, safe for commercial and personal use. It's a clean, sterile, odourless substrate. 

Vermiculite looks like mica with its stacked layers, which are what gives it such good water retention properties. It can retain both water and nutrients in higher levels than substrates like perlite, making it popular for roots, seedlings, propagating, and plants that like staying moist and don't tolerate drying out. It wouldn't be my go-to for cacti and succulents though, so do take your plant's needs into account. When making your own custom mix, a generous scoop is plenty, mixed in well, to help your own mix retain water and nutrients.

How does vermiculite work?

I think of vermiculite as teeny weeny sponges. It holds water, yet also drains when saturated, just like a sponge. Roots love it. They grow around the little vermiculite particles and just suck in whatever moisture they need, when they need it. But because vermiculite takes a long time to dry out, moisture is always there for the plant, enabling it to grow faster and healthier, reducing the risk of drying out. Handy for inconsistent waterers (like me), and for plants who throw a wobbly if left dry for too long. 

When is vermiculite used?

Vermiculite is a common ingredient in a lot of soil mixes, used to increase water and nutrient retention. A popular addition for plants that dislike drying out. Most often used for seed starting, and for having on hand to make custom potting mixes. It helps lighten heavy, compacted soil. It's a goody for moisture-loving plants and for fast growers. It acts like a sponge, so retains water for when roots need it. Commonly mixed with perlite and soil. 

Best used for:

Starting seeds > Vermiculite holds moisture better than perlite which helps keep seeds from drying out during germination.

Repotting > Especially when repotting outdoor container plants, as potted plants tend to dry out faster outside, especially if they’re in porous containers like terracotta.

Dry times > If you garden in a dry climate, or your air is dry inside and you find your indoor plants constantly need watering, add more vermiculite to your soil or soilless mix to conserves moisture.

Shallow roots > Some plants have shallow roots, so retaining moisture nearer the surface is more important (in a typical potting mix water is retained at the bottom of the pot). Instead of mixing vermiculite in, add a layer to the surface of the soil to retain moisture on top (a popular trick when sowing seeds also to provide lightweight, protective cover).

Should you use vermiculite or perlite?  

Often confused, and quite different, but often used together to get the best of both. Perlite and vermiculite are both lightweight. Both used for soil-less potting mixes. Both used to improve aeration and texture in heavy, compacted soils. Both have no odour, are sterile, non-toxic, free of disease, insects and seeds. Neither will break down, rot or decompose. Both are popular for seed germination and propagation, hydroponics and container gardening. Both are common ingredients in custom soil mixes made to suit the plant being potted up.

The differences come in how they retain water, how much water they can retain, and for how long, making them suitable for different uses. Vermiculite actually 'sucks in' water like a sponge, holding on to it for longer, and taking longer to dry out. Whereas perlite captures water in its surface layers, but doesn't absorb it as such, so dries out much faster.


Vermiculite is the better choice for plants that enjoy lots of moisture and don't handle drying out. Perlite dries out too quickly for moisture-loving plants. However the amount of water that vermiculite holds would be too much for cacti, succulents and other plants that prefer substrates on the much dryer, more free-draining side of life.