Everything You’ve Ever Wanted to Know About Perlite (A Guide to Hydroponics and Growing in Soil)

Perlite is a versatile growing medium that can be used for both soil-based growing and hydroponics. This material is lightweight and porous, making it suitable as an additive to horticultural substrates or as a standalone growing medium in hydroponic systems. In our guide, you will learn how to use perlite in the garden and for indoor and hydroponic growing.

Perlite is naturally occurring volcanic glass that expands to several times its original volume when heated to approximately 850-900 °C. The result is a lightweight, porous material that resembles crushed popcorn. Perlite is widely used in various industries, especially for plant cultivation, but also in construction, industrial filters and as a carrier for chemicals. Perlite is chemically inert (inactive), sterile, non-toxic and highly stable.

Benefits of perlite for growing in soil

Soil aeration: Perlite is porous and creates air pockets in the soil, giving roots better access to oxygen. This helps create a more abundant, resilient and healthier root system, which is reflected in plant vitality.

Improved drainage: When mixed into soil, perlite affects its water-retention properties. The growing medium drains better and retains less water, helping to prevent overwatering. This is particularly beneficial when growing species prone to root rot.

Preventing soil compaction: When growing in pots or raised beds, soil gradually becomes compacted over time. Lightweight horticultural growing media containing perlite retain their water-retention properties for longer, keeping the soil loose for a long time.

How to use perlite when growing in soil

For aerating soil in outdoor beds: When creating a new bed or planting, mix perlite with soil, peat or horticultural substrate in a 1:1 ratio.

When growing in pots: Mix horticultural substrate with perlite in a 3:1 ratio. The resulting mix will drain better than the original, unlightened substrate.

Germination: Perlite is an excellent medium for germinating seeds because it retains moisture without becoming waterlogged. Create a mix for germination and raising seedlings by combining perlite and peat in a 1:1 ratio. Remember that neither perlite nor peat contains available nutrients, so young seedlings will need to be transplanted or fertilised soon.

Perlite in hydroponics

Hydroponics is a method of growing plants without soil, based on nutrient-rich water (nutrient solution) and an inert growing medium. This can be rockwool, expanded clay, coconut substrate or perlite. Perlite does not retain water and is suitable only for certain types of hydroponic systems: drip irrigation, DWC, NFT, wick methods, Dutch bucket systems or the AutoPot system. Perlite is not suitable as a growing medium in flood trays, for hand watering or for other methods.

Hydroponic systems that use perlite as a growing medium

• AutoPot – Unique self-watering systems for indoor and outdoor use that do not require an electrical connection. The ideal growing medium for use with an AutoPot pot is a mix containing 50% perlite and soil or coco.
• Atami Wilma – Popular hydroponic systems in various sizes, with drip irrigation for indoor growing.
• Terra Aquatica – A leading range of hydroponic systems, inspired by hydroponics pioneer Wiliam Texier. The range includes various types of hydroponic systems suitable for indoor and outdoor use, propagation trays and fertilisers.

Perlite has a neutral pH and does not react with the nutrient solution in hydroponic systems. However, it still needs to be replaced regularly, as algae can accumulate in its pores, causing the surface to turn green. When using perlite in irrigation systems, watch out for small particles and dust, which can clog filters and drippers.

Would you like to learn more about hydroponics and indoor growing? Visit our Higarden blog to discover the latest developments in the world of growing and useful advice for growers.