Lighten Up! Learn How Vermiculite Can Improve Your Potting Mix
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Have you ever struggled with keeping a plant happy? Maybe your soil is too heavy and suffocating its roots, or perhaps it drains too quickly and dries out before your plant can thrive. If so, then vermiculite might be the answer you’ve been looking for! So, grab your gardening tools and learn how this mineral can help your plants flourish.
What is Vermiculite?
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.
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The Benefits of Using Vermiculite
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).
Photo: Mariia Boiko
How to Use Vermiculite
Vermiculite can be used in several ways to start seeds:
- Sow seeds in a mix of equal parts seed starter and vermiculite.
- Omit the soil, and just sow your seeds in vermiculite only. This will help to prevent new seedlings from damping off.
- Sprinkle a thin layer of fine vermiculite over newly planted seeds to keep them moist, and protect them from temperature swings while germinating. It also helps prevent damping off.
- Some people spread it on a newly planted lawn to keep grass seed from drying out, but it must be kept moist to prevent it from blowing away. Read our tips for lawn seeding.
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!
A Word of Warning: Handle With Care
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.
The Pros and Cons of Using Vermiculite
| Pros | Cons |
|---|---|
| Lightens heavy soil | Considered a non-renewable resource |
| Sterile | Asbestos contamination in some products |
| Absorbs water and nutrients and slowly releases them | Contains no nutrients |
| Aids drainage and aeration | Can blow away if not kept moist or mixed deeply into soil |
| Prevents seedlings from damping off | Wear gloves, goggles, and a dust mask when handling it |
Should I Use Vermiculite or Perlite?
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!
Robin Sweetser
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