Perlite is a lightweight granular material that’s white in colour. It seems and looks like little pieces of polystyrene, but they are actually made from volcanic glass that has been heated to 1000°C and “popped” into many times its original size. It’s lightweight, sterile, and easy to handle, and is long-lasting. It’s neither alkaline nor acidic.
Because it has expanded, perlite is very porous and can soak up water. However, it also makes drainage better, so it is great to mix into compost to make sure water can flow easily. Perlite is particularly useful in plant propagation, including taking cuttings and sowing seeds. Other materials that perform similar functions are vermiculite, grit and sharp sand.
If you’ve browsed the potting soil and seed starting mix aisle at your local garden center, you’ve likely come across perlite and vermiculite. These two soil amendments are incredibly useful for improving drainage, aeration, and moisture retention in all kinds of growing media. But can you use perlite and vermiculite together?
The short answer is yes! In fact, using a blend of perlite and vermiculite together in potting mixes provides the perfect balance of water retention and drainage that most plants thrive in.
In this article we’ll compare perlite vs. vermiculite, explain how each amendment works, and discuss the benefits of combining them in your potting mixes and seed starting blends.
Perlite vs. Vermiculite: How Are They Different?
Though they are often confused for each other, perlite and vermiculite are actually quite different soil amendments with unique properties.
What is Perlite?
Perlite consists of small, lightweight balls made by heating volcanic glass to a very high temperature. This causes the glass to expand and create countless tiny air pockets within each piece.
As a soil amendment, perlite has an extremely porous structure that retains very little moisture. Instead, it creates space for air pockets within the growing medium, improving drainage and aeration.
What is Vermiculite?
Vermiculite is a sponge-like mineral formed by heating mica until it expands. Unlike perlite, vermiculite has a very high water holding capacity. The plate-like structure of vermiculite acts like a series of little sponges to retain and slowly release moisture to plant roots.
While perlite creates air space, vermiculite retains actual moisture. This key difference makes them perfectly complementary amendments when used together.
Benefits of Mixing Perlite and Vermiculite
By blending perlite and vermiculite into your potting soils and seed starting mixes, you get the perfect compromise between moisture retention and free drainage. Here are some of the benefits this duo provides:
- Improves moisture retention while still draining well
- Allows more air flow to plant roots
- Reduces compaction and improves texture of dense soils
- Lightens heavy clay soils to make them loose and workable
- Holds moisture longer in seed starting mixes to prevent drying out
- Helps conserve water by retaining moisture between waterings
- Aerates and loosens overly dense, compacted soils
Additionally, the bright white perlite particles reflect sunlight well, helping illuminate and warm the entire root zone. Vermiculite provides spaces for beneficial root colonizing fungi to thrive.
How to Blend Perlite and Vermiculite in Mixes
A general recipe is equal parts perlite, vermiculite, peat or coco coir, and compost. However, you can adjust the ratios to suit your specific needs.
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For seed starting, use more vermiculite to retain moisture.
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For cacti and succulents, use more perlite to create very fast drainage.
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For moisture-loving plants like calathea, use more vermiculite to hold water.
A good starting blend for most houseplants or garden plants is:
- 1 part perlite
- 1 part vermiculite
- 2 parts peat or coco coir
- 2 parts compost
Mix the ingredients together thoroughly before filling pots and seed trays. Blend them into existing garden beds as well.
If purchasing a commercial blend, check that it contains both perlite and vermiculite, along with organic material for nutrients.
Perlite vs Vermiculite: Which is Better For Seed Starting?
While both perlite and vermiculite are useful in seed starting mixes, vermiculite is generally considered superior for starting seeds. Its incredible water retaining abilities prevent seeds from drying out during germination, while still providing adequate aeration.
However, many gardeners prefer to use a blend of both, since adding some perlite improves drainage and airflow to prevent mold, fungi, and damping off diseases.
If you use just perlite in seed starting mixes, you’ll likely need to water constantly to prevent drying out. For seeds, a higher ratio of vermiculite is ideal.
Can You Use Too Much Perlite or Vermiculite?
When used in moderation, perlite and vermiculite provide the ideal soil structure for most plants. However, it is possible to add too much of a good thing! Here are some potential issues:
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Excessive perlite can hold too much air and dry out quickly, especially for seedlings. It may need constant watering.
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Too much vermiculite retains overly high moisture, potentially leading to root rot, fungi, or other problems.
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Very high ratios of either amendment may make the medium too loose and unstable for larger plants.
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Too much perlite or vermiculite without enough organic material may poorly anchor plants and provide fewer nutrients.
Start with the recommended equal parts ratio, then adjust based on your specific soil needs. Focus on creating the right balance of air and moisture retention for your particular plants’ preferences.
Are There Any Drawbacks to Perlite and Vermiculite?
Perlite and vermiculite provide such perfect growing conditions that they are suitable components for nearly any gardening project! However, there are a couple small drawbacks:
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Vermiculite holds moisture, but does not provide any actual nutrition. Regular fertilizing is still essential.
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Perlite floats up to the top of pots over time and will need remixing when repotting.
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Both amendments are very lightweight and may blow away in strong winds if used in outdoor beds.
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Vermiculite can sometimes contain low levels of asbestos, requiring extra safety precautions.
However, with proper care taken, there are no significant downsides to using perlite and vermiculite together in your soil. The benefits far outweigh any potential disadvantages!
Perlite and Vermiculite: Better Together
For creating the ideal balance of moisture retention, drainage, and aeration in potting mixes, you really can’t beat the power duo of perlite and vermiculite together.
Follow the recommended 1:1:2 ratio of perlite, vermiculite, and organic components for thriving plants. Adjust as needed to suit the preferences of your specific vegetation.
With the yin and yang balance these two amendments provide, your plants will have everything they need to establish strong, healthy root systems and achieve their maximum potential.
Frequency of Entity Occurrences
Perlite: 28 times
Vermiculite: 27 times
Soil/Mix/Medium: 16 times
Moisture: 13 times
Drainage: 8 times
Air: 7 times
Seed Starting: 6 times
Water: 5 times
Plants: 5 times
Potting Mix: 4 times
Aeration: 4 times
Taking care when using perlite
Perlite is dusty, so take care to avoid inhaling the dust. Dampen with water before using it. If you want to use a whole bag of perlite at once, add a few liters of water, seal the top, and shake it. Then wait twenty-five minutes before using it.
Use perlite when taking cuttings
Perlite can aid water retention in compost, which can help improve the chances of your cuttings taking root. To do this, you need a type of compost that is made just for cuttings. This type of compost has a finer texture and less nutrients than general-use multi-purpose compost. Add 50/50 perlite to the compost mix, fill the pots, water them well, and then let the compost mix drain for a few hours before putting your cuttings in it.
Cuttings can also be rooted in perlite on its own. Moisten the perlite and fill a polythene bag around a third full. Cut softwood or semi-ripe cuttings just below a leaf joint and take off the leaves from the bottom half to two-thirds of the cutting. Put the shoot’s bare bottom into the perlite, then blow air into the bag and close the lid. After several weeks, roots should start to form. Once roots are well developed, the cutting can be taken out and potted up in compost.
Perlite vs Vermiculite
FAQ
Can I mix perlite and vermiculite together?
When not to use perlite?
What is the ratio of perlite to vermiculite mix?
Can you plant straight into vermiculite?
Can you mix perlite and vermiculite?
You can absolutely mix perlite and vermiculite together to use in your soil. This will help with some water retention properties while also helping drain the soil and improving soil aeration. The combination is usually not necessary for most plants, as they either like well-drained soil, or they like consistently moist soil.
Should you use perlite or vermiculite in your garden?
Perlite and vermiculite are two common soil amendments that gardeners use for seed starting, adding to potting mix, and even growing hydroponically. These minerals are often used to improve the quality of the soil and each has its own unique benefits. But which one should you use in your garden? Here’s what I’ve learned over the years about both.
How much perlite & vermiculite should I put in my soil?
As much as you need, of course, but as a general rule don’t exceed 50% perlite or vermiculite in your soil, potting mix or growing medium. The rest can be compost, peat (substitute) or just soil etc. But keep in mind that these are soil improvers, they are not soil!
Is perlite better than vermiculite?
A: Perlite is better for improving soil aeration and drainage, while vermiculite excels at retaining water and nutrients. Perlite has a porous, irregular surface, and vermiculite has a layered, golden-brown appearance. Q: When should I use perlite?
