Soil Amendments Explained: Perlite, Vermiculite, Peat Moss & Coco Coir
Healthy plants start with healthy soil — and that’s where soil amendments come in.
Whether you’re starting seeds, growing in pots, or improving garden beds, soil amendments play a key role in how well your plants grow. In this post, we’ll explain what soil amendments are and break down four of the most commonly used ones: perlite, vermiculite, peat moss, and coco coir.
What Are Soil Amendments?
Soil amendments are materials added to soil or growing mixes to improve structure and performance. Rather than feeding plants directly like fertilisers, amendments help soil hold water better, drain excess moisture, improve airflow, and create a healthier environment for roots.
They’re especially useful for:
- Seed starting
- Pot plants and containers
- Improving compacted, sandy, or poor-quality soil
Using the right amendment can make a noticeable difference in plant health and growth.
Perlite: For Drainage & Airflow
Perlite is a lightweight, white material made from expanded volcanic rock.
Why use perlite?
- Improves drainage
- Increases airflow around roots
- Prevents soil from becoming compacted
Perlite is ideal for plants that dislike sitting in wet soil, such as succulents, cacti, and many indoor plants. It’s also commonly added to seedling mixes to keep roots well-oxygenated.
Best for:
Seedlings, cuttings, houseplants, succulents, and cacti.
Vermiculite: For Moisture Retention
Vermiculite is a soft, flaky mineral that expands when heated.
Why use vermiculite?
- Holds moisture and nutrients
- Releases water slowly to plant roots
- Helps keep soil evenly moist
Because it retains water so well, vermiculite is particularly useful when germinating seeds and growing young seedlings that need consistent moisture.
Best for:
Seed starting, seedlings, and moisture-loving plants.
Peat Moss: For Lightening & Conditioning Soil
Peat moss is made from partially decomposed organic material and is commonly used in potting and seedling mixes.
Why use peat moss?
- Improves moisture retention
- Lightens heavy soils
- Enhances overall soil structure
Peat moss is often used as a base ingredient in potting mixes and is especially helpful for improving sandy or nutrient-poor soils.
Best for:
Seedling mixes, pot plants, and improving soil texture.
Coco Coir: A Versatile, Natural Alternative
Coco coir is a natural fibre made from coconut husks.
Why use coco coir?
- Retains moisture while still allowing airflow
- Improves soil structure
- Long-lasting and slow to break down
Coco coir is a popular alternative to peat moss and works well in both seed starting and container gardening.
Best for:
Seed starting, pot plants, and general soil improvement.
Which Soil Amendment Should You Choose?
Each amendment serves a different purpose:
- Need better drainage? Choose perlite
- Need consistent moisture? Choose vermiculite
- Need to improve soil structure? Choose peat moss or coco coir
Often, the best results come from combining amendments to create a balanced growing mix suited to your plants’ needs.
Healthy soil is the foundation of a thriving garden. By understanding how soil amendments work, you can make better choices and give your plants the best possible start.