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Gardens in the Sky

TOP: Greenhouse operation using perlite soils to enhance root growth.

ABOVE: Propogating cutting in 100% perlite.

perlite is an important ingredient in potting soils

ABOVE: Perlite is a key ingredient in fine potting soils.

BELOW: Flowers propagated in perlite-enhanced potting soil.

propagating flowers in perlite soil roof gardens thrive using lightweight perlite in soil

ABOVE: Swiss Chard growing in the roof garden of an organic grocery store in Chicago.

BOTTOM: Orchid ODONTOGLOSSUM variety grown in perlite.

orchids are grow successfully in perlite

Perlite for Horticulture

When perlite ore is expanded or “popped” by rapid, controlled heating, it expands up to 15 times its original volume and takes on a foam-like cellular appearance — essentially clusters of microscopic glass bubbles, creating a porous structure. This physical transformation makes expanded perlite an extremely effective aggregate for use in horticultural growing mixes – or, by itself, as a medium in hydroponic growing and as a rooting medium. (For a detailed explanation of perlite expansion, see PDF Infosheet: Why Perlite Works).


The primary role of expanded perlite in soilless growing mixes is aeration when added to peat moss, composts, coir and other water-holding aggregates. The porous surface of expanded perlite provides room alternately for both air and water in the mixes – each needed for vigorous root growth. Different sizes of perlite are produced for this purpose, offering growers various amounts of air space after drainage. Usage rates by volume vary from 5% to 40% for potting mixes, and as high as 75% to 100% in green roofs and hydroponics applications. Perlite use is increasing in agricultural and turf grass applications to break up compacted soils and retain water in dry climates.

INformation sheets

(linked PDF files from the Perlite Institute Library)

—PROPAGATION

—GREEN ROOFS

—IN THE GROUND

—HYDROPONICS

—GROWING MEDIA