What is vermiculite for?

How much vermiculite/perlite

Part 3, salt chlorine generator basics! mmilos, has made some good points about salt chlorine generators (SCGs)/electrolytic chlorine generators (ECGs), and some need clarification. I will refer to them as SCGs, and to the AutoPilot brand in particular. There are many types of SCGs on the market from various manufacturers and they will each have their own requirements in water balance, rules on operation, specific type of salt that should be used, length of cell life, etc., so be sure to brief yourself with the owner’s manual. General ideas on how the systems work are basically the same. First, let’s talk about salt. Not all salt is the same. Where it is mined and how it is produced/manufacturing method can affect the amount of impurities and additives found in the salt, which directly relates to the risk associated with levels of stain-causing minerals that can be found in it. Salt in your pool will be measured in parts per million (ppm). Salt facts: sea water – 35,000 ppm; saline solution for contact lenses – 6,000 ppm; and the human body – 4,000 ppm. Your taste level for salt is about 3,500 ppm. An AutoPilot SCG requires only 2,500 – 3,000 ppm for operation. Chlorine in a pool is also measured in ppm. 4 ppm of chlorine is 10x as corrosive on stainless steel as 4,000 ppm of salt. With new technology today, there are many salt friendly pool components such as dive boards, hand rails, ladders, etc. With this information, the corrosion factor should not be an issue in today’s market. If you still have concerns, you may want to consider a sacrificial anode. A sacrificial anode is a component that can be added to your plumbing and attaches to your bonding wire. It contains a zinc anode, which will sacrifice itself to galvanic corrosion, before all metals in the pool, such as lights, ladders, rails, etc. These anodes typically need replacing at the 3 year mark. Learn more here: http://www.poolspanews.com/water/stain-free-salt-chlorination.aspx http://www.autopilot.com/why-buy-autopilot http://www.pooltool.com/anodes.html Second, let’s talk about how SCGs work. Once your SCG system is installed and your first addition of salt and conditioner/stabilizer/cyanuric acid is made and dissolved, your pool professional will tell you when and at what output level to start your SCG. Conditioner/Stabilizer/cyanuric acid basically protects the sun from taking the chlorine out of pool, letting it do its job as a sanitizer longer. As pool water (which will now contain the 3,000 ppm of salt) passes through your SCG system, and makes contact with the titanium coated cell blades, an electrolytic process occurs and CREATES CHLORINE on site and on demand. This is the biggest misconception with SCGs. SCG pools still sanitize with chlorine. What does creating chlorine on site, on demand mean for you? A purer chlorine, and the fact that you should not have to purchase expensive chlorine, store it, handle it, administer it, etc. – or shock (to oxidize). Some SCGs may not be able to operate until the pool water temperature is at a certain level. Until that specific temperature is met (day and night water temperature) you will use additions of granular chlorine to sanitize (it is a dichlor, tablets are a trichlor, and there is a difference, tablets should never be used with an SCG, as they may damage the system). Other negative water conditions may require a supplement of granular chlorine, but this should be rare and only suggested by a pool professional. To increase or decrease the chlorine output on an SCG, you will simply press a button, same for shocking. If you have an SCG, there will be an initial addition of salt, and through water analysis performed by your pool professional, additions will be made accordingly to keep you at the optimal level. Salt levels lower through dilution – rain and topping off the pool with hose water due to water loss from evaporation and swimmers/splash out. This chlorine that is created by your system is more pure than let’s say a chlorine tablet. A chlorine tablet for example is composed of 3 parts – chlorine (used to sanitize), cyanuric acid (protects chlorine from the sun, should be about 25-50 ppm), and inert ingredient (ingredients that hold the tablet together). Each time you add a tablet into the pool water, you are adding these 3. Higher summer temperatures and higher bather loads create an increase in chlorine demand for sanitizing, which means more tablets. Over time, after adding all these tablets, the cyanuric acid will accumulate over the 50 ppm max. The cheapest, easiest, best result remedy to high cyanuric acid is dilution – draining a portion of the pool and refilling it with fresh water. If this dilution process is not performed the cyanuric acid will lower the pH and alkalinity, creating unbalanced water, leading to faster degradation of your pool components, and can lead to ear, eye and skin infections. When pH and alkalinity are not at levels they should be, chlorine cannot be as effective of a sanitizer as it can be, which only compounds the issue even more. The lower pH and alkalinity due high cyanuric acid levels will not react well, or even at all, to pH and alkalinity increasers, as the high cyanuric acid “holds them down”. Diluting the cyanuric acid level with the fresh water will lessen its ability to “hold down” the pH and alkalinity, allowing them to rise naturally, eventually rising enough, closer to normal ranges, where the use of increasers will actually work. This is a widely debated issue between industry professionals/experts/scientists/chemists, but through many years of experience, this is just the way it works, no sense in fighting it. Many of our customers have been ecstatic with the results of the dilution process and even more so when they actually act on our suggestion of converting to the SCG system instead of using tablets. Obviously, when using an SCG, water balance is easier to maintain. Other benefits include less harsh on hair, skin, and eyes, which has a lot to do with the fact of better water balance. Smooth, silkier feel to the water. It is also nicer to have a machine put chlorine into your pool instead of having to monitor and add chlorine to the pool yourself. You will still need to perform home testing every 2-3 days to monitor chlorine, pH, alkalinity, etc. levels, and have your pool professional perform an analysis every 2 weeks to help ensure you are on the right track with water balance. This covers part 3 of your questions. I hope this basic information helps. Consult your pool professional for more information on SCGs and which system will best suit your needs. AutoPilot has been producing SCGs since 1976 and I’ve been selling them since 1984. I personally have had an AutoPilot on my pool for 13 years (as long as I’ve owned my pool). I have replaced the cell, as they only produce a certain poundage of chlorine per lifetime, depending on which cell you purchase. I will never use chlorine in tablet/stick/liquid form again! Learn more about AutoPilot SCGs here: http://www.autopilot.com/ Good luck with your research and if you have any other questions, please let me know!

What is vermiculite?

This natural mineral is used in many sectors, from the building industry to gardening. It’s the common name for hydrated laminar magnesium-aluminum-ironsilicate. You can find out more about its geology at Mineral Galleries – Vermiculite.

Why is it helpful to gardeners?

You can use it to encourage seed germination and improve soil structure. This is because of its aeration and water-holding properties.


  • It’s a very lightweight material
  • Does not rot
  • Improves soil structure through soil aeration
  • Increases water and nutrient retention

Where does its name come from? It rings a bell…

You may be thinking of ‘vermiculture’, where worms are used to help decompose food waste. Both come from the Latin word ‘vermiculare’ meaning to breed worms.

This is because when vermiculite is heated, it expands into long strands resembling small worms. The American experimenter Thomas H. Webb first named it back in 1824. You can find out more in How Products Are Made – Vermiculite

Where and when should I use it?

You can mix it into composts and it’s great for hydroponic systems. Vermiculite’s insulating properties means it is particularly good when you need to cover seedlings.

What size should I get?

The smallest size of vermiculite is best used to germinate seeds. If you want to use it as a soil improver, opt for the largest size for the best results.

Video: How to mix vermiculite with your compost

It’s already in our ready-made composts – the shiny material is vermiculite. It’s easy to add it to your home-made compost too. Just take a look at this video:

Where to buy vermiculite

Would you like to buy some to encourage seed germination and improve soil structure? We sell different grades of Large, Medium and Fine. You can buy it online in 35 litre and 60 litre bags.

Not sure if it’s right for you?

Just give us a call on 01432 853111 or drop us an email at [email protected] if you’d like more information.

Vermiculite: Uses for growing plants, safety, and comparison to Perlite

Anyone who has ever worked with a potting soil mix has probably noticed those little “blocks” or chunks of gold it contains. Light and airy, these particles are known as vermiculite, an important product in gardening (and many other industries). While they may not be worth their weight in gold they are highly revered for their numerous benefits.

How Vermiculite is made

Similar in nature to perlite, vermiculite is formed by the weathering or heating of biotite or phlogopite. These rocks are considered phyllosilicates, containing high proportions of magnesium aluminum silicate mineral that resembles mica in appearance. A typical chemical analysis of commercial vermiculite shows it contains 38-46% silicon oxide (SiO2), 16-35% magnesium oxide (MgO), 10-16% aluminum oxide (Al2O3), 8-16% water, plus lesser amounts of several other chemicals.

After mining, the ore is separated from other minerals and screened to classify it into different particle sizes. Like perlite, these different sizes comprise the different grades of vermiculite: large, medium, fine, superfine and micron. The most commonly used sizes are 0–2, 2–4, and 4–8 mm in diameter (1).

The particles are then superheated in a process called exfoliation (2) to create elongated, accordion-like particles. Expanded vermiculite is typically golden brown in color.

Two features of vermiculite lead to its unique shape and numerous uses.

  1. A layered, crystalline structure within the mineral provides the hinged plates that make the material expand or unfold in a linear manner, like an accordion, when heated.
  2. Trapped water flashes into steam when heated, forcing the layers open.

Uses of Vermiculite

Both treated and untreated vermiculite are used across a variety of industries, for many different purposes. Expanded vermiculite is versatile and unique: it is lightweight, it is non-combustible, compressible, highly absorbent, pH neutral, inert, and non-reactive to all but very strong acids.

  • Gardening – helps with water retention, soil aeration, and drainage. Used as the sole growing media in containers, or a component of potting soil; also used as a soil amendment for garden soils. You can shop now on Amazon, Espoma is our favorite brand currently.

  • Animal feed – works well as carrying medium for certain types of nutrients: vitamin preparations, fat concentrations, and molasses.

  • Packing material – commonly used when shipping hazardous liquids. Highly absorbent so it will soak up any leaks that occur; non-flammable nature contains fires (when packaging items such as lithium batteries) to inside the container. Unlike standard packing peanuts, it breaks down naturally in landfills.

  • Automotive – used to make brake and clutch linings, gaskets, and rubber seals. When ground, into a powder it can be used in auto paints and lacquers.

  • Construction – used to manufacture plasters, loose-fill insulation, and lightweight concrete used for floors and roofs.

Pros and cons

As with other products such as perlite, peat moss, and coconut coir, vermiculite has both its advantages and disadvantages. In the horticulture industry, the advantages far outweigh the downfalls.


  • pH close to neutral.
  • High water retention.
  • Takes a long time for particles to dry out so the root zone stays wet longer.
  • Holds onto nutrients well (high cation exchange capacity) because of platy structure.
  • It can be used alone or mixed with other media to create potting mixes.
  • Its sterile nature makes it highly suitable for starting seeds. There is little risk of root rot or damping-off (3).
  • Great for seed germination or plant propagation as the particles let plants be pulled from the perlite without damage to the root systems when it’s time for transplanting.
  • Reusable year after year since it doesn’t decompose.


  • Holds onto too much moisture for some plants.
  • Carbonate compounds foster alkaline reactions, raising pH in the root zone.
  • Nonrenewable resource. Although more readily available than peat moss, it isn’t considered renewable like coconut coir.
  • Difficult to find in the retail home gardening marketplace.

When to use Vermiculite for plants

When not used as a soil conditioner, or as an ingredient in a soilless potting mix, there are three other situations vermiculite is useful for plants.

Sole growing media

Vermiculite is used as a growing media for seed starting and rooting propagated cuttings because of its sterile nature and ability to retain moisture without encouraging damping-off. All plants can be started – from seeds or cuttings – using vermiculite as the sole growing media. When the time comes to pot up plants into containers some will thrive growing solely in vermiculite, some prefer other types of growing media for maximum plant growth.

Herbs that prefer moist soils that thrive in vermiculite:

  • Basil
  • Coriander
  • Parsley

Moisture-loving plants that thrive in vermiculite:

  • Ferns
  • Spider plant
  • Pothos
  • Philodendron
  • Lucky bamboo

Seeding new lawns

One of the critical aspects of establishing a new lawn is keeping seeds moist while they germinate. When seeding new lawns spread ¼” layer across the newly seeded area, then irrigate well. The vermiculite helps to hold water close to the seeds as they sprout.

Storing bulbs

Tender varieties of bulbs are dug up in the late fall and then stored in a cool, dry place over the winter. Layer bulbs in-between vermiculite before storing. It will soak up excess moisture without desiccating the bulbs.

Vermiculite versus Perlite

Again, many gardeners wonder if there is a big difference between vermiculite and perlite and if they can be substituted for one another. Unfortunately, while they have some similar properties they act very differently.

The biggest difference between the two products is that perlite helps increase the drainage, while vermiculite increases water retention by absorbing water in its plate-like structure and holding it in the root zone for plant roots. Use perlite when you are growing plants that benefit from the growing media drying out completely between waterings (succulents, orchids); use vermiculite when you are growing plants that prefer to be kept moist such as tropical plants.

When using them as ingredients in potting mixes or as a soil amendment, perlite and vermiculite act as complements to one another versus alternatives.

A quick note about safety

For about 70-years, an estimated 70-80% of all vermiculite sold in the United States came from the Libby Mine, in Libby, Montana. The vermiculite deposit was found to have naturally occurring asbestos minerals directly alongside the vermiculite. When mined by the Zonolite Company, Libby Amphibole asbestos (LAA) contaminated the product, creating health and safety concerns, especially with vermiculite being used in attic insulation and as raw materials in many other construction products.

Asbestos exposure is incredibly dangerous, posing many health risks. When inhaled, asbestos fibers enter the lungs and are known to cause lung cancer, mesothelioma, and other lung diseases.

This mine was closed in 1990; in 1999 the Environmental protection Agency (EPA) stepped in to investigate concerns from local citizens and begin remediation. The Libby cleanup project has been one of the largest, longest-running, remediation projects to date.

According to The Vermiculite Association, all vermiculite mined and used today is mined under strict protocols to ensure its safety.


Known for its sterile, lightweight nature and ability to retain moisture, improve aeration, and increase drainage, vermiculite is an invaluable asset to the horticultural industry. It is typically used for germinating seeds and rooting cuttings, as an ingredient in soilless growing media, and as a soil conditioner for garden soil. Known to be inexpensive, effective, and safe for use, it is a great tool to keep in your gardening arsenal.

perlite vs vermiculite: What is the best growing medium for hydroponics?

Both have been around for many years as a soil additive. They both also have life in the world of hydroponics, as a great compliment to each other.

In hydroponics, the growing medium, such as the perlite or vermiculite, takes the place of the dirt or soil. Not by providing the nutrients.

That is what the water flow does. It is so the roots will support the weight of the plant(s) and hold it straight up.

Pros and Cons of Perlite and Vermiculite in Hydroponics

Perlite used by itself, though rarely, because of its light weight. The downside in certain hydroponic systems the water interacts with the growing media.

Thus, shifting it around too much and could wash it away. It is much better as a mixture with other mediums, like vermiculite.

A mixture of 50 – 50 is a very common scenario, you will want to use the large grade perlite, a size #3 or #4.

Perlite also has good wicking action which for a wick-type hydroponic system is ideal. Perlite is also cheap and easy to find.

There are a couple of drawbacks to perlite in hydroponics. It doesn’t keep water and the dust is not something you should be breathing in.

Considered a nuisance dust it will bother your eyes, throat, and lungs. You should always wear some kind of a dust mask when using it.

Mix Your Own Soilless Potting Mix for Hydroponics

Here is how the two work so well together. Vermiculite retains moisture. Perlite doesn’t. Use that 50-50 mixture as a growing medium in your drip type hydroponic system as well as an ebb and flow type system.

It will keep the water and nutrients and still supply the roots with plenty of oxygen. Vermiculite is also cheap but tends to be a little harder to find.

There is one major drawback of vermiculite. It retains so much water, if used by itself it will suffocate the roots of the plants.

In Conclusion

Both, perlite and vermiculite can improve your soil conditions. Such as aerating your soil, so more oxygen can get to the roots and improving water retention, or lack of.

They are both used in the hydroponics industry as a soil-less medium. You should now understand the difference between the two.

They are not interchangeable. This will be helpful when you are looking for your next soil additive or hydroponic medium. Your plants will thrive.



The term vermiculite applies to a group of minerals characterized by their ability to expand into long, worm-like strands when heated. This expansion process is called exfoliation. The name vermiculite is derived from a combination of the Latin word vermiculare meaning “to breed worms,” and the English suffix-ite, meaning mineral or rock. In its expanded form, vermiculite has a very low density and thermal conductivity, which makes it attractive for use as a soil amendment, lightweight construction aggregate, and thermal insulation filler. Expanded vermiculite also has a very large chemically active surface area, which makes it useful as an absorbent in some chemical processes. When vermiculite is ground into a fine powder, it is used as a filler in inks, paints, plastics, and other materials.


Vermiculite and its unique properties were known as early as 1824, when Thomas H. Webb experimented with it in Worcester, Massachusetts. It was Webb who gave the mineral its fanciful name because he thought the long strands looked like a mass of small worms. Vermiculite was regarded as not much more than a scientific curiosity until the early 1900s when more practical uses were sought. The first commercial mining effort occurred in 1915 in Colorado. The material was sold as tung ash, but did not find sufficient buyers, and the venture failed. The first successful vermiculite mine was started by the Zonolite Company in Libby, Montana, in 1923. The mine continued to operate until 1990.

The largest vermiculite mining operation in the world is located in the Phalabowra (also sometimes spelled Palabora) district of the Republic of South Africa. Other countries producing significant amounts of vermiculite include the United States, China, Russia, Brazil, Japan, Zimbabwe, and Australia.

In 1999, there were three active vermiculite mining operations in the United States, two in South Carolina and one in Virginia, which shipped concentrated vermiculite ore to exfoliation plants located throughout the country. In addition to using concentrated vermiculite from domestic mining operations, these plants also imported about 77,000 tons (70,000 metric tons) of concentrated vermiculite from foreign sources—mostly South Africa.

Raw Materials

Technically, vermiculite encompasses a large group of hydrated laminar magnesium-aluminum-iron silicates, which resemble mica. There are two keys to the unique properties of vermiculite. The first is its laminar (or layered) crystalline structure, which provides the hinged plates that make the material expand or unfold in a linear manner, like an accordion. The second is the fact that it contains trapped water, which flashes into steam when heated to force the layers open. There are a great many naturally occurring vermiculite minerals and soils, and their identification often requires sophisticated scientific analysis.

One of the most common forms of vermiculite is generally known as commercial vermiculite. This is the form that is mined and processed for various end uses. It is derived from rocks containing large crystals of the minerals biotite and iron-bearing phlogopite. As these rocks are exposed to the weather, they start to decompose, allowing water to enter and react with the various chemicals present. As the decomposition and chemical reactions proceed, vermiculite is formed.

When commercial vermiculite flakes are heated and expanded, they undergo a color change that depends on the chemicals present and the temperature of the furnace. The resulting expanded vermiculite granules are usually a gold-brown color with a bulk density of about 4-10 lb/cu ft (64-160 kg/cu m), depending on the size of the granules.

The Manufacturing Process

The manufacturing process used to produce commercial expanded vermiculite consists of two separate operations. The mining and concentrating operations that produce raw vermiculite flakes are conducted at one location. The exfoliation and classifying operations that produce various sizes of lightweight, expanded vermiculite granules for use in other products are conducted in another location. Sometimes these two locations can be half a world apart.

There are many different methods used in both of these operations. The exact methods vary from mine to mine and plant to plant. Here is a typical manufacturing process used to produce commercial expanded vermiculite.


  • l Rocks containing vermiculite are dug from a huge open pit in the ground. The soil on top of the rocks, called the overburden, is removed with power shovels or earth scrapers. The exposed rock layers are then drilled with large pneumatic or hydraulic drills, and the holes are filled with explosive charges. When all personnel and equipment have been moved out of the area, the explosive charges are detonated.
  • 2 The resulting heap of loose rocks are scooped up with power shovels and dumped into trucks or train cars, which carry the rocks to a nearby processing plant.


  • 3 The rocks are fed through a series of crushers and screens to reduce their size. The vermiculite is separated from the surrounding rocks and dirt using various wet or dry techniques depending on the particular mining operation and local environmental regulations. These techniques may include froth flotation, gravity separations, winnowing, or electrostatic separation. In each of these techniques, either the vermiculite itself or the other materials are trapped and separated from each other until the resulting vermiculite flakes are about 90% pure by weight.
  • 4 The vermiculite flakes extracted from various sections of the mine may be blended together before further processing to ensure uniformity of the product.


  • 5 The separated vermiculite flakes are sorted by size. This may be done with a series of screens or it may be done in a long enclosed wind tunnel . In the wind tunnel, the flakes are fed into the upstream end of the tunnel and are carried along the length of the tunnel by the flow of air. The larger flakes, being heavier, fall out of the air stream first and are caught in a hopper at the bottom of the tunnel. This separation by weight continues down the length of the tunnel until all the flakes are caught in hoppers. By controlling the length of each hopper opening and the velocity of the air, the flakes can be sorted into various sizes, or grades, ranging from about 0.63 in (16 mm) down to about 0.02 in (0.8 mm) in diameter. If the particular vermiculite being mined tends to form a high percentage of large flakes, the flakes may be slightly crushed to delaminate them and reduce their size. This process is called debooking and allows the flakes to be quickly heated during the exfoliation process.
  • 6 The graded vermiculite flakes are dumped into large plastic bags or other containers for shipping to various exfoliation A diagram depicting the processing of vermiculite. plants. If the flakes are to be shipped to plants overseas, they are loaded in bulk into the holds of ships for transport.


  • 7 The vermiculite flakes are transported by truck or train from the port or mine to the exfoliation plant, where they are offloaded and stored in a covered area to protect them from contaminants and the weather. It is important to prevent the flakes from absorbing moisture. Otherwise, it will take too much energy to heat the flakes to the required temperature to make them expand.
  • 8 The flakes are loaded onto a conveyor belt and lifted to the top of a 20-25 ft (6.1-7.6 m) high vertical furnace lined with ceramic bricks. As the flakes fall down the length of the furnace, they pass through one or more burners fired by natural gas . The temperature inside the furnace reaches approximately 1,000-1,500°F (540-810°C), which is sufficient to make the trapped water in the flakes flash to steam and cause the flakes to expand into worm-like particles. At the bottom of the furnace, the particles slide down an inclined plane. This delays the exit of the particles from the furnace and allows the vermiculite to be heated further in order to reach full expansion. Other exfoliation plants may use different furnace configurations, but the general sequence of operations is similar.


  • 9 The hot, expanded vermiculite particles are then drawn up a vertical tube by a vacuum. Any small stones or other solid contaminants are too heavy to be carried upward by the gentle flow of air and fall out the bottom of the tube. The air flow also acts to cool the hot vermiculite.
  • 10 If a customer or application requires fine particles, the vermiculite may be ground and screened to produce a specific size or range of sizes before it is packaged for shipping. In some exfoliation plants, the larger particles may also be screened or sorted into various sizes, depending on the final use.
  • 11 The sorted, or classified, vermiculite particles are then deposited into storage hoppers, where they are dispensed into individual 4-6 cu ft (0.10-0.15 cu m) paper or plastic bags for retail sales or placed into larger 50 cu ft (1.3 cu m) bags for use in various commercial applications. The bags are sealed, labeled, and moved to a warehouse for shipping.

Health Aspects

Vermiculite ore deposits may also contain a variety of other materials such as mica, quartz, and feldspar. These deposits vary from one mining location to another. During the manufacturing process, some of these materials may pose potential health hazards to workers. In the United States and many other countries, these hazards are defined in Material Safety Data Sheets (MSDS), which identify the hazard and provide information on the safe handling and disposal of the material.

One of the most common health hazards in processing vermiculite comes from quartz, which is crystalline silica. It is usually only present as larger particles, but when it is ground into finer particles, the dust can be inhaled and cause a lung disease called silicosis. As a result, strict dust control and personal protection measures are incorporated into those areas of the vermiculite-processing operation where the materials are ground, sifted, and bagged. At the consumer level, exposure to silica dust is negligible and does not pose a health hazard.

In some vermiculite ore deposits, there may also be certain amounts of various forms of asbestos. None of the ore bodies currently used by major vermiculite producers pose an asbestos health risk to workers when the material is processed in accordance with the applicable MSDS. In August 2000, the United States Environmental Protection Agency (EPA) issued a report regarding vermiculite sold as a soil amendment. In the report, they concluded there was little or no risk to consumers from asbestos.

The Future

Although there are several other materials that may be used as a substitute for vermiculite, vermiculite’s extremely low density and thermal conductivity continue to make it attractive for many applications. In 1999, it was estimated there were approximately 55 million tons (50 million metric tons) of vermiculite reserves in the world.

Where to Learn More


Hombostel, Caleb. “Vermiculite.” In Construction Materials: Types, Uses, and Applications. New York: John Wiley & Sons, Inc., 1991.


Hindman, James R. “Vermiculite as an Industrial Mineral” (1997). http://www.mcn.net/~vermiculite/overview.htm (March 22, 2000).

Hindman, James R. “Vermiculite Products and Applications.” (1997). http://www.mcn.net/~vermiculite/uses.htm (March 22, 2000).

The Schundler Company. “Basic Vermiculite Information and Data.” http://www.schundler.com/techverm.htm (May 18, 2000).

The Vermiculite Association. “About Vermiculite.” http://www.vermiculite.org (May 18, 2000).

— Chris Cavette

What Is Vermiculite: Tips On Using Vermiculite Growing Medium

We all know that plants require soil aeration, nutrition and water to thrive. If you find that your garden soil is lacking in any or all of these arenas, there’s something that you can add to improve the soil structure — vermiculite. What is vermiculite and how is using vermiculite as a growing medium beneficial to the soil?

What is Vermiculite?

Vermiculite can be found in potting soil or purchased by itself in four different sizes for gardening with vermiculite. Germinate seeds using the smallest size of vermiculite as a growing medium and the largest size for improved soil aeration.

Vermiculite is the name of a group of hydrated laminar minerals (aluminum-iron magnesium silicates) which look like mica. Horticultural vermiculite is processed with massive heat that expands it into accordion shaped pellets composed of multiple layers of thin plates. It will not rot, deteriorate, or mold and is enduring, odorless, non-toxic and sterile.

Vermiculite is generally a neutral 7.0 but is dependent upon the source from around the globe and its reaction is alkaline. It is very lightweight and mixes easily with other mediums.

Vermiculite Uses

Vermiculite added to the garden or vermiculite in potting soil increases water and nutrient retention and aerates the soil, resulting in healthier, more robust plants. Perlite

may also be found in potting soils, but vermiculite is far superior for water retention. Vermiculite, although less aerating than perlite, is the amendment of choice for water-loving plants. Here are other uses for vermiculite:

  • Add vermiculite to soil for conditioning and lightening either alone or in conjunction with peat or compost. This will accelerate the growth and promote anchorage for tender young root systems.
  • Using vermiculite as growing medium will also enable the plant to more easily absorb the ammonium, potassium, calcium and magnesium necessary for vigorous growth.
  • Medium grade vermiculite can be used directly for root cuttings. Just water thoroughly and insert the cutting up to the node.
  • Use vermiculite alone or mixed with soil or peat for seed germination. This will allow seeds to germinate more rapidly. If vermiculite is used without soil, feed the seedlings a weak fertilizer solution (1 tablespoon of soluble fertilizer per 1 gallon of water) once the first leaves appear. Damping off is thwarted since vermiculite is sterile and the seedlings are easily removed without damage to the roots.
  • Vermiculite mixed half and half with soil, peat or compost eliminates packed down soil in flower pots and houseplant containers while allowing excellent aeration, reducing watering frequency and allowing root spread.
  • To transplant using vermiculite, dig a hole 6 inches larger than the plants roots. Fill in with a mix of vermiculite and the removed topsoil. Again, this allows for root spread, provides moisture control and protects the roots from drying out due to sun or wind. Three inches of vermiculite can also be used as mulch around shrubs and other garden plants like roses, dahlias, tomatoes.
  • Place bulbs or root crops in a container and pour the vermiculite around them. The sponge-like quality of the vermiculite will absorb any excess moisture and prevent rot or mildew while protecting them from temperature fluxes.
  • Even newly seeded lawns can benefit from an application of vermiculite. Mix 3 cubic feet of vermiculite per 100 square feet, seed, then cover the entire area with ¼ inch of vermiculite. Water in with a fine spray. The vermiculite will hasten germination and increase the number of seeds that germinate while maintaining moisture and protecting from drying and heat.
  • Lastly, vermiculite can be used when arranging flowers. Fill the container with vermiculite, thoroughly saturate with water, pour off the excess and arrange the flowers. This eliminates the need to change the water, eliminates spills and keeps blooms fresh for day. Just be sure to use horticultural vermiculite and not that sold for house insulation — it is treated to repel water!

New Tool Determines if Vermiculite Insulation Contains Asbestos

Scientists with the United States Geology Survey (USGS) have created a hand-held spectrometer to determine if vermiculite insulation contains deadly amphibole asbestos.

The recent innovation should provide a time-saving technique for commercial and home inspectors.

Currently, inspectors must send samples to off-site laboratories before making that determination.

“The emphasis was coming up with a method that was both reliable and easier to use,” Gregg Swayze, USGS scientist and lead researcher, told Asbestos.com. “We achieved that goal.”

The findings were published in the April 2 edition of American Mineralogist.

Vermiculite insulation is no longer used in new construction, but an estimated one million homes in the U.S. still have it, according to the USGS.

Vermiculite is a naturally occurring mineral that is perfectly safe when pure. Unfortunately, an estimated 75 percent of it came from Libby, Montana, where it usually was contaminated with toxic amphibole asbestos.

Exposure to asbestos is the main cause of mesothelioma, an aggressive and deadly cancer.

Some Vermiculite Is Safe

Vermiculite used in the U.S. also was mined in Louisa, Virginia; Enoree, South Carolina; Palabora, South Africa; and Jiangsu, China.

Asbestos is rarely found in the vermiculite that comes from these locations.

“Vermiculite from Libby has a distinct signature that sets it apart,” Swayze said. “It’s erroneous to think all the vermiculite is from Libby. It is not.”

The spectrometer works by identifying the source, which involves differences in elemental composition that are measured by electron probe microanalysis.

Swayze and his team examined 52 vermiculite samples from the five sites, including those from attic insulation, horticultural products and commercial packing materials.

Asbestos was found in all of the nearly two dozen samples from Libby, but little or none was found in the vermiculite from the other four sites.

Vermiculite Mostly Found in Attics

The vermiculite from Libby is part of the longest man-made environmental disaster in American history. It was mined there for more than 50 years, ending in 1990.

The insulation, which was known by the brand name Zonolite, is most often found in residential attics.

What made the Libby vermiculite so dangerous was its proximity to asbestos deposits.

Decades of mining the vermiculite mixed with asbestos fibers led to the death of hundreds of residents in Libby and thousands more who are suffering from various asbestos-related diseases.

The United States Environmental Protection Agency (EPA) began its cleanup of Libby in 1999.

In 2002, the EPA declared the site a public health emergency, officially giving it Superfund status, a federally funded priority.

Latest Tool Could Accelerate the Process

The portable spectrometer will allow inspectors to make the asbestos determination in a matter of moments, allowing remediation decisions to be made much sooner.

It also would be useful to have the information before a major home renovation project begins, eliminating the uncertainty that exists when insulation is disturbed. No amount of asbestos exposure is safe, according to the experts.

Although this technology was patented in 2014, it has yet to be used commercially. The recent journal report in American Mineralogist is expected to spark the licensing procedure.

The projected cost of the spectrometer is $50,000, making it pricey for an individual homeowner but potentially attractive for an inspection company looking to streamline its work.

Connect with a Mesothelioma Doctor Find a Top Specialist Near You Get Help Now

Growing Tomatoes in Containers

Q: Hi Mike! I just finished your “You Bet your Tomatoes” book and I’m considering trying my hand at growing some this year. But I rent, and will be moving early next year, so I’m hesitant to dig up the lawn to make a garden for just one season. Is it possible to grow any sort of tomato crop in large pots? Or should I just put it off until next year, when I will have a garden of my own? Thanks.

    —Kelly in Reading PA

A. Thank you, Kelly, for the opportunity to announce that the classic tomato growing book you so kindly mentioned (don’t worry; your check is in the mail) is being reissued in a brand new edition by Plain White Press this Spring! It should be on bookstore shelves as we speak—eh, read.
Now: You should definitely try a few plants this year. A little experience even on a small scale will help you greatly when you grow ‘for real’ next season.
But you have choices beyond just ‘tamatas in pots’ or ‘no tamatas at all’. Could you possibly ‘share-crop’ a couple of plants with a gardening friend who wouldn’t mind your putting a couple of plants in the ground; or a community garden where you could get—or share—a plot for the season? Either option would actually be preferable to containers, as there would be other gardeners around to hold your hand and teach you the tricks that will allow you to really hit the ground running next season.
Otherwise, absolutely buy some nice big containers! I get good tamata results in pots that are 17 inches high and 20 inches across the top. Yours don’t have to be that exact size—anything close to it should be fine—but they DO have to be big. You can grow things like peppers in smaller containers, but tomatoes need a lot of room. And only one plant per pot, although you can grow other things in there as well. (We’ll get to that in a minute.)
Don’t fill those containers with lousy, weedy outside dirt; it’s darned near impossible to keep plants alive in that stuff when they’re imprisoned in a pot. Find a nice ‘soil-free’ potting mix; these lightweight blends of natural substances like peat, perlite and vermiculite are available at virtually all garden centers (just avoid the ones laced with Miracle-Gro or other nasty chemicals). Then mix some nice yard-waste compost—bagged or bulk—in with the potting soil; about ¼ compost and ¾ mix. (Don’t go nuts measuring; this is cooking, not baking.)
Note: Gardens Alive potting soil already contains some nutrients like worm castings—and added minerals that are highly beneficial to plants and otherwise hard to find—so you can cut back a little on the added compost if you use it or a similar product.
Oh: No peanuts, pebbles or other nonsense in the bottom; your plants want to be able to send their roots all the way down.
Find a spot for your pots where water can drain freely out the bottoms and fill the pots up right there. Even a lightweight mix can become heavy in pots that size, and it’s better to fill them up where they’re going to stay. (Don’t bother buying saucers for underneath; you don’t want to water to sit down there—all it can do is drown your plants and breed mosquitoes.)
To get the most out of your pots, use them to grow cool weather crops like lettuce and other salad greens early in the season—before you could safely put out your tamatas. Water your mix well, spread the seeds of a nice leaf lettuce or salad green mix overtop, cover the seeds with a thin layer of potting mix and mist it well. Cover the top at night with clear plastic to retain heat, but take the plastic off during the day. Spritz the surface daily and the lettuce should sprout in about five or six days. No more plastic after that.
Let the lettuce grow until it’s three or four inches high and then begin to harvest it with scissors ‘cut and come again’ style, mostly from around the edges, letting the plants in the middle grow. The cut lettuce will regrow, and you should be able to make several harvests before tomato-planting time arrives (which in Reading would be between May 15th and June 1st.). Then harvest the center plants and install your purchased tomato plants. (Don’t try and start your own tomato plants from seed the first year; get used to killing grown plants outdoors before you move up to killing little tiny ones indoors.) Continue to harvest the ‘outside’ lettuce until it turns bitter, then replace it with some trailing nasturtiums for spicy good eating or some small flowers, “chust for nice”.
If you want to keep things simple, grow bush-style determinate plants; they can get by with the support provided by a large store-bought tomato cage or similar structure. Indeterminate plants, like the big beefsteaks, can be grown in large containers, but you have to enclose them in full-sized tomato cages made of welded wire animal fencing.
Q. You have always advised us to plant our tomatoes deeply in the ground. Would you bury them the same way in a container?

    —Janice in Woodbury, New Jersey

A. Absolutely, Janice! Tomatoes develop auxiliary roots along their buried stem; and planting half of the stem under the soil line to grow those extra roots provides many benefits. While you’re at it, add a dozen crushed eggshells to the hole to provide calcium; it’ll improve their flavor and prevent blossom end rot.
Click HERE for a previous Question of the Week with lots more details on growing in containers.
Click HERE for one on the use of eggshells with tomatoes; and HERE for one filled with basic tamata growing tips.

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