Picture this: You're excited to grow plants and buy potting soil, only to find polystyrene-like white balls mixed in. Potting soil should be natural, so why the bean bag beads? Actually, those little white balls aren't synthetic. They're perlite, an ingredient that provides nutrients and improves water drainage.
What are the Little White Balls? Are They Bean Bag Beads?
The small styrofoam-like particles are a mineral called perlite. It's made when lava rock cools, trapping moisture inside. When heated, the water expands, causing the rock to 'pop' and become less dense. That's why it's sometimes called 'volcanic popcorn.'
How is Perlite Made?
Perlite is a type of volcanic glass (SiO2) with high water content from hydrated obsidian rock. When heated, it expands and becomes up to thirteen times lighter. Horticultural perlite is made by heating SiO2 glass from mines to high temperatures, causing it to expand by over 1,000 per cent. The result is a lightweight mineral perfect for potting mixes. Under a microscope, perlite comprises many tiny cells, like a sponge, that hold water and provide a soil water reservoir.
Why is There Perlite in Potting Soil?
Potting soil aims to promote healthy plant growth, and perlite offers multiple benefits:
Aeration
Perlite's tiny pores provide potent aeration, keeping the soil loose around roots and preventing compaction. Some call it 'air for the soil.'
Moisture Delivery
Perlite's porous structure holds onto water, providing roots with intermittent moisture and reducing the risk of drying out.
Are White Balls in Potting Soil Always Perlite?
Ideally, potting mixes should use perlite, a natural substance formed from cooling lava flows. However, some vendors use cheaper imitations that damage the environment, such as polystyrene bean bag beads. Check the label for perlite. If it contains styrofoam or other plastic-derived compounds, switch brands to avoid adding plastic to the environment.
Sometimes perlite is mistaken for gypsum, a mineral made of calcium and sulphur used to break up compact soil and provide aeration. Gypsum also fertilizes the soil with calcium and sulphur ions. Some mixes contain both, so refer to the ingredients label.
Is Perlite Dangerous?
Perlite isn't hazardous but is classified as a nuisance dust. It can throw fine particles into the air, causing reactions for some. Wear mouth and eye protection when using large quantities, and those with asthma should be especially careful.
Is Perlite an Organic Substance?
Chemically, perlite isn't organic because it contains silicon, not carbon. However, from a gardening perspective, it's considered organic because it's natural and doesn't undergo synthetic processes. It's similar to fish fertilizer or seaweed emulsion and safe for organic horticulture.
How to Use Perlite
Here's how to use perlite:
Taking Cuttings
Perlite retains moisture, improving the chances of cuttings taking root. Mix fine-textured compost with perlite in a 50:50 ratio, water, and allow to drain before adding cuttings. You can also grow cuttings in perlite alone by wetting the granules, placing them in a polythene bag with the cuttings, and transplanting once roots appear.
Seed Sowing
Mix perlite with compost in a 50:50 ratio, moisten, sow seeds, and cover with a fine layer of perlite to trap moisture and allow light to enter.
Draining
Add perlite to the soil to aid drainage. Mix one part perlite to four parts soil, dig up the affected area, and replace the soil to improve drainage in compacted areas.
Perlite and Bean Bag Beads
Perlite and bean bag beads are different, though they may look similar. Perlite is volcanic glass, while bean bag fillings are usually plastic or dried beans. Some soil vendors use polystyrene, adding to the confusion. Both provide the same function in the soil, but perlite is natural, while plastic beads are synthetic. In that sense, the fillings of bean bags and potting mix are sometimes the same.
Bottom Line
Those little white balls are perlite, volcanic glass heated to over 870 degrees with ultra-low density. It supports soil drainage and improves aeration, great for potting mixes and recovering compacted soil.