Have you ever looked at your potting soil closely?
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If you have you may have noticed a white or off white granular material that's mixed into the soil. This is especially prominent when using compost to sow seeds, take cuttings or even re-pot a house plant.
These substances are Vermiculite & Perlite.
These two handy substances are a godsend to all gardeners. They can make compost drain better and also retain moisture, even though that sounds like a contradiction.
So lets dig into it, What is vermiculite? What is Perlite? What do they do? What's the difference? Which one should you choose?, here’s all you need to know...
Also known as "volcanic popcorn", Perlite is made of amorphous volcanic glass and is typically formed by the hydration of obsidian. It is a white granular material that is made by heating volcanic glass until it expands and ‘pops’, like popcorn. It is sterile, lightweight and has a neutral pH, so it’s very easy to work with.
Perlite for plants - When mixed with compost, it traps air pockets in the compost, which improves drainage. Perlite is often used in propagating cuttings, where free-draining compost is needed, or in sowing seeds.
Because it is porous, perlite soil absorbs water and can be used to improve moisture retention in compost, but its primary use is to improve drainage.
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Perlite is most often mixed with composts to improve drainage. Here are a few of the most common uses:
A 1:4 mix of perlite and compost makes a free-draining potting medium ideal for succulents.
Softwood and semi-ripe cuttings will root well in perlite. Part-fill, a plastic bag with moistened perlite, insert the cuttings and seal the bag. After several weeks, roots will start to form. Once the roots are well developed, the cuttings can be potted on.
Perlite is very dusty, so dampen it with water before using it to avoid inhaling the dust.
Vermiculite is produced by heating a naturally occurring mineral (magnesium aluminium iron silicate) so that it expands. Like Perlite it is also a naturally occurring mineral.
Horticultural vermiculite is used for planting looks like small golden-brown flakes. It can absorb up to four times its own weight in water and will also absorb some minerals that plants need, such as potassium, magnesium and calcium.
Vermiculite for plants - Its water retention means it's the best when it comes to water retention and is ideal for potting up plants that need moist compost. It is sold as medium or fine grade – medium grade is better used in cuttings composts and fine grades in seed sowing.
NB: Don’t get horticultural vermiculite (sold in garden centres) mixed up with the vermiculite insulation granules sold in hardware stores – they are not interchangeable!
Vermiculite is mainly used to improve moisture retention. Here are a few examples:
A 50/50 mix of compost and vermiculite is perfect for houseplants that need a lot of water, such as maidenhair fern.
30% medium-grade vermiculite added to compost makes a suitable medium for cuttings and potting on seedlings.
Scattering a light covering of vermiculite on compost after sowing seeds helps keep moisture in and reduces the risk of ‘damping off’ when seedlings are attacked by a fungus that causes them to collapse.
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Are you interested in learning more about Lithium magnesium silicate? Contact us today to secure an expert consultation!
Perlite and Vermiculite are very, very similar. But there are a few key differences.
Vermiculite is better for water retention, that also means in that moisture it retains key nutrients for your plants and cuttings to soak up.
Perlite works better to help drainage, this means its also better for loosening heavy, compacted soil. So if you have clay soil perlite will be your best friend throughout the winter months.
Both work well for blending into potting mixes, are approved for organic gardening and neither decompose in soil, so once added you will forever reap the rewards.
Vermiculite and perlite are just two of the many valuable products you’ll find in our centre.
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Vermiculite is made from mica-like minerals that expand when heated, the thin flakes that make up its structure pulling away from each other. This creates long strands that look like worms, hence the “verm” in its name. By the time we get a bag of vermiculite, the “worms” have been broken apart into smaller chunks that, on close inspection, look like little accordions.
When buying vermiculite, you will see grades that range from coarse to extra fine, depending on the size of the pieces.
Vermiculite is an amazing material that boasts a unique set of properties. It aerates the soil, helping to improve drainage, but it also holds water and nutrients, absorbing up to three times its weight in liquid that it releases slowly, like a sponge. It is best for plants that like moist soil, not succulents or cacti.
If you have heavy clay soil, mixing in vermiculite can help lighten it up. If your soil is so sandy that it doesn’t retain water, vermiculite will help it hold more moisture. Though it doesn’t totally deteriorate, it may compress over time, especially when mixed with heavy soil, and its ability to hold water and air will lessen. For this reason it is not recommended for use in growing long-term crops.
It contains trace minerals, including potassium, magnesium, and calcium, but no real plant nutrition. The pH is usually neutral but can range from 7 to 9, depending on the country of origin (check out what your plants’ pH requirements are).
Vermiculite can be used in several ways to start seeds:
As a rule of thumb, the larger the seed, the coarser the grade that can be used.
Vermiculite for Propagation: Root cuttings in a mix of potting soil and vermiculite or omit the soil and use it alone. It will keep the cuttings moist while they form strong roots.
Vermiculite for Planting: It is a great addition to potting soil, lightening it, preventing compaction, aiding drainage, and increasing its ability to hold water. It will keep you from overwatering and underwatering as it absorbs water while letting the excess drain and releases the retained moisture to the roots as they need it. It is best used for plants that like moist soil. Learn how to make your own potting mix!
The EPA conducted tests on garden products containing vermiculite, and though it found trace amounts of asbestos in some, it determined that home gardeners faced only a minimal health risk. They advise us to use it in a well-ventilated area and moisten it to keep the dust down. Needless to say, you want to avoid inhaling it and skin contact.
Vermiculite has been used for years for home insulation. Unfortunately, much of that older insulation came from a mine that also had asbestos in it. If you have vermiculite insulation in your home, you are advised not to disturb it. If it is leaking into your living space and you need to have it removed, consult a licensed asbestos removal contractor in your area.
While vermiculite and perlite share many similarities, there are instances where one is better suited than the other.
Vermiculite is good for drainage and aeration, but it can expand and hold water like a sponge, releasing it as plant roots need it. This makes it perfect for use with plants that need moist soil.
Perlite is especially good at drainage, providing channels for water and air to flow through the soil. It absorbs very little liquid, making it ideal for plants that need dry conditions, such as succulents, cacti, and some orchids. Learn more about perlite.
Vermiculite offers a unique set of properties that can significantly improve the health and happiness of your plants. By addressing drainage, aeration, and moisture retention, it acts as a true workhorse in the potting mix. Whether you’re starting seeds, propagating new life, or nurturing established plants, it can be a valuable tool in your gardening arsenal.
Ready to take your gardening game to the next level? Grab a bag of vermiculite and see the difference it can make!
Have you ever used vermiculite in your garden or with your house plants? Do you have any tips or tricks for using it? Tell us about it in the comments below!