What Is Perlite Seed Starter?

Description

• Perlite is a naturally occurring igneous mineral, technically a volcanic glass. Perlite is high in moisture content, which gives it a unique property: it expands to many times its original size when heated. Imagine if you were to shatter a pane of glass into tiny pieces and heated them until they popped like popcorn kernels. Perlite rock is treated thus to produce the finished product used in seed mixes. The perlite kernels even exhibit a white color like popcorn. The expanded pieces of perlite are irregular in shape and unique in a way similar to snowflakes. They are light in weight, porous and can be safely handled, although they can be somewhat abrasive.

Perlite in Seed Mixes

• Perlite is used in many different seed mix types. It can be blended with sphagnum peat moss, sand, vermiculite, loam or compost, or any combination of these materials. It is chemically neutral, so it will not affect the pH of any mixture or soil. It serves the purpose of adding water- and air-retention capabilities to seed mixes. The irregular structure of the kernels also helps to promote root branching of young plants, an important part of growing healthy, strong seedlings. Perlite may also be used alone as a seed starting mix. Its light weight makes it especially suitable for small seeds which may have trouble pushing up through heavier soils or mixes.

Advantages

• Perlite holds a significant amount of water for its weight, helping avoid the drying out of seed mixes. Unlike dark soils which absorb light, its white color helps reflect light, adding to the available light for seedlings which may have been started in less than ideal light conditions. Perlite is very lightweight, weighing as little as 2 lb. per cubic foot. The irregular nature of the kernels helps perlite hold air and water, and therefore nutrients, well. This helps reduce the frequency of watering or fertilizing needed.

Availability

• Perlite is very common, being widely available at almost every garden center or greenhouse that sells potting supplies. It is also an ingredient in almost every brand of commercial potting soil or seed starting mix on the market.

Other Horticultural Uses

• Perlite is also used by many hydroponic growers as a growing medium. Its physical qualities and chemical inertness make it ideal for many applications of this type. It can also be used in mixes or alone as a rooting medium for cuttings.