Perlite, a light granular material, is white in colour. Although it looks and feels similar to small pieces of polystyrene, it is made from expanded volcanic glass heated to 1000°C. It then ‘pops’ (like popcorn), to many times its original size. It is lightweight, sterile and easy to use. It is neither acidic nor alkaline. Perlite in compost brings lots of benefits to your soil, so you definitely should consider adding this material to your list.
Why is Pertile Useful?
Perlite’s porous nature makes it very porous. It can absorb water but also improve drainage. Perlite is great to be mixed into compost to allow water to drain freely. Perlite is especially useful for plant propagation. It can be used to take cuttings or sow seeds. Vermiculite and sharp sand are other materials that can perform similar functions.
How to Use Perlite in Compost?
Add to Composts
Perlite can be added to potting compost to help succulents and other plants that are sensitive to moisture. Perlite traps air in the compost, encouraging water to flow through. This ensures that the roots of the plants will not be left in damp soil. Mix perlite and compost in a ratio of approximately 1:4 before planting to ensure a uniform mix.
Perlite is a good way to retain water in compost. This can increase the likelihood of your cuttings to take root. This is why you will need a compost specifically made for cuttings. It should have a finer texture, lower nutrient content and a lower nutrient count than the general multi-purpose compost. Mix 50:50 perlite into the compost mixture, then fill the pots with water. After the compost has drained, let the compost dry for several hours before inserting the cuttings.
Perlite can be used to root cuttings. Place the perlite in a container and moisten it. Cut softwood or semi-ripe wood cuttings just below the leaf joint. Then, remove the leaves from the lower half to two thirds of the cutting. The shoot’s lower portion should be inserted into the perlite. Seal the bag by filling it with air. Roots should begin to form after several weeks. After roots have developed, you can take the cut and plant it in compost.
To create a moist environment for delicate seedling roots, mix perlite with cuttings compost in a 50:50 ratio. Perlite can also be used to cover seeds that need light to germinate. The perlite allows light through while still keeping the seed moist.
Should You Use Perlite in Compost or Vermiculite?
Vermiculite, a naturally occurring mineral, is heated to extremely high temperatures to expand it. It is sold in bags of brown-gold flakes at a garden centre. It can absorb as much as four times its weight water.
Perlite has lower water and nutrient retention, so vermiculite is best for plants that require more moisture. Vermiculite protects seedlings from damping off and other fungal diseases. Perlite can also retain water but is used primarily to aerate compost. Perlite is great for making a free-draining compost for plants that require good drainage like succulents and cacti. It can also be used to make a light compost for seedlings.
Perlite and vermiculite can be used together. Mixing a bit of perlite in a seed mix will ensure that the roots are nourished, and a layer of vermiculite will keep the moisture in.
Caution When Using Perlite in Compost
Perlite can be dusty so, avoid inhaling it. Before using perlite, make sure to let it dry with water. To use a bag full of perlite in one batch, add a few litres of water to the bag. Seal the top, shake the bag and let it sit for a quarter of an hour.