Horticultural uses of Perlite and Vermiculite

Perlite and vermiculite have been used for years to amend professional potting soils made from peat moss (called "soilless" mixes or artificial soils because they literally contain no soil). They also have been used in outdoor mixes, in turf grass and outdoor plantings, for gardens, for special 100% Perlite or vermiculite growing applications, and increasingly for commercial and amateur hydroponic growing and water conservation (especially in landscaping and gardening).

Essentially Perlite and vermiculite are used in the horticultural industry because they both provide aeration and drainage, they can retain and hold substantial amounts of water and later release it as needed, they are sterile and free from diseases, they have a fairly neutral pH (especially Perlite which is neutral), and they are readily available, non-toxic, safe to use, and relatively inexpensive. As a rule of thumb, Perlite tends to last longer, has a more neutral pH, and functions much better in hydroponics, outdoor applications, lawns and gardens (in part because it is stronger). Nevertheless, for decades they both have been used by professionals dedicated amateurs and gardeners.


A complete description and all the uses of Perlite


A complete description and all the uses of Vermiculite


A list of all the guides provided by The Perlite Institute (at ) and The Schundler Company

Horticultural Perlite:

What is Perlite? ---

Perlite is a unique volcanic mineral, which expands from four to twenty times its original volume when it is quickly heated to a temperature of approximately 1600-17000 F. This expansion is due to the presence of two to six percent combined water in the crude Perlite rock, which causes the Perlite to pop in a manner similar to that of popcorn. When expanded, each granular, snow-white particle of Perlite is sterile with a neutral pH and contains many tiny, closed cells or bubbles. The surface of each particle is covered with tiny cavities, which provide an extremely large surface area. These surfaces hold moisture and nutrients and make them available to plant roots. In addition, because of the physical shape of each particle, air passages are formed which provide optimum aeration and drainage. Because Perlite is sterile, it is free of disease, seeds, and insects.

Perlite has been used for many years throughout the world for soil conditioning and as a component of growing mixes with materials such as peat moss or bark. Extensive studies have shown that the unique capillary action of Perlite makes it a superior growing media for hydroponic cultures.

Among the many uses of Perlite today are propagation and seed cultivation, plug production and transplants, interiorscape and planter growing, composting, hydroponic cultures, turf and lawns, and around shrubs, trees, and landscaping.

Propagation and Seed Cultivation ---Commercial growers and hobby gardeners have found that Perlite is an ideal medium for rooting cuttings. Through the use of cuttings rooted in horticultural Perlite, the time to first production may be reduced by as much as 40%.

Perlite mixes of fine Perlite alone can be used as a seed-starting medium because of the ease of maintaining uniform moisture and temperature levels. Perlite's bright white colour makes it particularly effective as a seed cover offering protection against bright sunlight and high radiant energy as well as resistance to surface moss or algae growth. In addition, Perlite's white colour reflects light up under plant foliage, which further enhances growth.

In India, it has been found that when seeds are sown with small quantities of fine Perlite in field crops, there is a much higher rate of germination and a measurable increase in yields.

Plug Production/Transplants ---Commercial plug plant production in greenhouses showcase Perlite's role in water and nutrient conservation. Water retention by horticultural Perlite is not an indiscriminate action. The amount of water adsorbed on the surface of Perlite is a function of particle size. Coarser Perlite particles adsorb less water than finer grades ---thus the amount of retained moisture that is desired can be regulated to suit particular requirements.

Perlite's ability to cling to roots and root hairs and the friable nature of a Perlite mix reduces transplant shock, which increases survival rates.

Reduced production time, conservation of water and nutrients, reduced labour and shipping costs, and increased survival rates all confirm horticultural Perlite's long and enviable record of performance throughout the world.

Rooftop, Interiorscape and Planter Growing ---The advantages of horticultural Perlite are readily seen in rooftop applications, planters, and interiorscape displays where weight is a factor. Wet sandy loam weights about 120-140 lbs/ft3(1920-2240 kg/m3; Perlite and peat mixed in equal volumes will weigh only about 35 lbs/ft3 (560 kg/m3. This difference can be critical where supporting structures such as roofs must be considered. Increasingly, 100% Perlite applications are being used both by home gardeners and commercial growers (See -Container Growing with 100% Perlite and Perlite /Peat Mixes and/or Using 100% Fine Perlite in Israel for Commercial Planters and Containers at ).

Composting ---Recycling as a result of shrinking landfill disposal areas has increased interest in composting in home gardens and by commercial enterprises and municipalities. Studies at Cook College of Rutgers University reveal that additions of Perlite to compost piles speed decomposition of leaves, grass clippings, and other yard waste. In addition, the use of Perlite reduces the amount of labour required to periodically turn piles to insure proper aeration. When composting is completed and the compost is put to use, the Perlite will continue to perform for many years as it lightens and aerates the soil while increasing its water holding ability. (See - Composting with Perlite at ).

Hydroponic Culture ---The fastest growing application for Perlite in the horticultural field is in hydroponic culture. Perlite exhibits a unique capillary action in that nutrient rich water can be drawn up from a reservoir through a fine Perlite growing media at the rate that is required by a plant. As a result, plants grown in Perlite do not suffer from over watering or under watering.

Tomato crops grown hydroponically in Perlite have produced average yields 7% higher than tomatoes grown in rockwool. Currently throughout the world many table vegetables are being grown in hydroponic grow bags; melons are being grown in Florida (See Growing Melons in Perlite Hydroponic Cultures in Florida at ), and in Holland and the US, commercial cut flowers, strawberries, and orchids are being grown in 100% hydroponic Perlite containers. (See the other Plant Guides on hydroponic applications listed earlier in this section.)

Turf and Lawns ---No grass is more highly stressed than stadium turf and golf greens. These are subject to the whims of nature as well as constant foot traffic and resulting compaction. Horticultural Perlite can provide an easy solution to this problem. When turf is renovated with Perlite, excess water will not pond yet an optimum amount of water will be retained for proper growth. Additionally, turf will be lush and green while the soil will remain soft for an extended period of time. (See - Horticultural Perlite Solves Compaction Problem at New Stadium at .)

For the landscaper or home gardener, fine and medium grades of Perlite will promote drainage and eliminate soil crusting in heavy clay soils. In addition, plant roots will more easily penetrate the Perlite/soil growing media. Most importantly, the lawn will hold much more water and not have to be watered nearly as much (See Expanded Perlite for Turf and Landscaping at .)

Shrubs, Trees, and Landscaping ---Fine and medium grades of horticultural Perlite is very effective in growing shrubs, trees, and in other landscaping applications. In addition to retaining water, which is vitally important in light of the growing shortage of water in many parts of the world, Perlite also aerates the growing medium. As landscaping applications are usually permanent in nature, fine and medium grades of horticultural Perlite are the ideal choice since they do not rot or otherwise decompose, and perform their water conservation/aeration roles for the life of the planting.

Horticultural Vermiculite:

Horticultural Vermiculite has the excellent property of improving soil aeration while retaining the moisture and nutrients necessary to feed roots, cuttings, and seeds for faster growth.

Like Perlite, horticultural vermiculite is permanent, clean, odourless, non-toxic and sterile. It will not deteriorate, turn mouldy or rot. The pH of vermiculite is essentially neutral (7.0-9.5) but owing to the presence of associated carbonate compounds; the reaction is normally alkaline. It also will vary (become more alkaline) with changes in processing techniques and time, and with the presence of moisture. The pH, colour and chemical composition of vermiculite also will vary from mine to mine.

Vermiculite possesses cation exchange properties; thus it can hold and make available to the growing plant ammonium, potassium, calcium and magnesium.

When mixed with peat, composted bark, organic compost, or natural soils, vermiculite like Perlite helps promote faster root growth, and gives quick anchorage to young roots. These mixes help retain air, plant food, and moisture, and release them as needed by the plant.

Because vermiculite is very light and easy to handle, it easily mixes with soil, peat, composted pine bark and other composted organic materials, fertilisers, pesticides and herbicides. And when used as a carrier or bulking agent, it ensures more even distribution.

Root Cuttings ---Medium grade vermiculite is the standard among professional nurserymen for many horticultural uses including the insertion of cuttings. Like fine grades of Perlite, these finer grades of vermiculite may be used directly as poured from the bag. Simply water the vermiculite thoroughly and insert the cuttings. And if the container has sufficient drainage, over wetting or watering normally is not a serious concern.

Soil Amending or Soil Conditioning---Where the native soil is heavy or sticky, gentle mixing of Perlite or vermiculite in proportions up to one-half the volume of the soil is recommended. This creates air channels and allows the soil mix to breathe. Mixing vermiculite in flower and vegetable gardens or in potted plants will provide the necessary air to maintain vigorous plant growth; and when soils are sandy, the use of vermiculite will help the soil hold the water and air needed for growth.

Seed Germination---Use vermiculite alone or mixed with soil or peat, and very little watering will be required. You will notice that not only more seeds will germinate, but also they will germinate faster. When vermiculite is used alone, seedlings should be fed with a weak fertiliser solution when the first true leaves appear. A tablespoon of soluble fertiliser per one gallon of water should be enough.

When vermiculite is mixed half-and-half with soil, peat, composted pine bark, or other properly composted soil materials, no additional feeding normally is required right up to the time of transplanting. Because vermiculite is sterile, the threat of what some professionals call "damping-off" is virtually eliminated. And later, seedlings can be removed from vermiculite with little danger of breaking off hair roots, and the dense root growth enables young plants to take hold immediately.

HousePlants and Containers---Vermiculite eliminates the problem of compacted soils in flowerpots. Mixed half-and-half with soil, peat, or composted soil products, it provides excellent aeration and moisture control, and it lightens the mix so larger pots can be placed on shelves or hung from the ceiling. In addition, vermiculite amended soils allow the roots in a flowerpot to spread out quicker and more evenly, and require far less watering.

Storing Bulbs and Root Crops---Pour vermiculite around bulbs placed in a container. If clumps with bulbs are dug out, allow to dry for a few hours in the sun and then place them in cartons or bushel baskets and cover with vermiculite. The absorptive power of vermiculite acts as a regulator that prevents mildew and moisture fluctuation during the storage period. It will not absorb moisture from the inside of stored tubers, but it does take up free water from the outside, preventing storage rot. Stored tubers are protected from even the most severe temperature changes.


The Perlite Institute (at ) and The Schundler Company have developed an extensive file of brief, but useful Plant Guides on the many uses of Perlite and vermiculite. We encourage you to read them!

Plant Guides on Potting Soils and Greenhouses:

Perlite Gradation and Peat/Perlite Mixtures

Container Growing with 100% Perlite and Perlite /Peat Mixes

Indoor Gardening with Perlite

Comparative Growth Studies Perlite vs. Polystyrene Media

Perlite vs. Polystyrene in Potting Mixes

The Concern over Fluorides

Using Perlite in Potted Plants

Cultivation of Spruce Seedlings in Mixtures of Perlite and Sphagnum Peat in Norway

Useful Links to Helpful Sites about Potting Soils and Container Growing

Plant Guides on Outdoor Gardening and Landscaping:

Expanded Perlite for Turf and Landscaping

Effective Watering with Horticultural Perlite (and Water Conservation)

Horticultural Perlite-The Natural Growing Media for Outdoor Gardening

Horticultural Perlite Solves Compaction Problem at New Stadium

Renovating Golf Greens with Horticultural Perlite

Composting With Perlite

Container Growing with 100% Perlite and Perlite /Peat Mixes

Using 100% Fine Perlite in Israel for Commercial Planters and Containers

Useful Links to Helpful Sites about Outdoor Gardening and Landscaping

Plant Guides on Hydroponics and 100% Perlite Systems:

The Role of Perlite in Hydroponic Culture

Growing Melons in Perlite Hydroponic Cultures in Florida

Hydroponic Culture of Strawberries in Perlite

Growing Orchids in Perlite

Useful Links to Helpful Sites about Hydroponics and Hydroponic Growing

Plant Guides on General Technical Standards and Properties:

Standard Gradations of Perlite---Fine, Medium, Coarse Defined

The pH of Vermiculite--Variable and Changing

Schundler Company Products and Brand names Described

For more information about these uses of Perlite and vermiculite, please contact :

The Schundler Company P.O. Box 513 Metuchen, New Jersey 08840
(ph)732-287-2244 (fax) 732-287-4185

© copyright 1999, P. A. Owen

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