Houseplants Under Lights

Lesson 2: Houseplant Containers & Potting Media

Potting Media Components -- Part 1

There are many possible potting media components. The following are most common.

Top Soil

This is a natural way to grow plants outside. Soil is not generally used for houseplants because of some inherent problems.

Advantages: Top soil is inexpensive and easily available in small quantities. Disadvantages: It may contain weed seeds, bacterial, fungus, and viral diseases. Therefore, it needs sterilization before use. Heavy soil may not allow enough air for proper root growth.

Compost

Compost is a natural ingredient in any potting mix. With the environmental movement today, many homeowners are being forced to compost. In some communities, a large scale composting operation exists to handle the grass clippings and leaves from the city parks. Still other communities collect leaves from homeowners in the fall and use it to make compost. The compost is then sold by the bag or truckload to local gardeners.

Advantages: It is inexpensive and generally weed free (providing the compost pile is heated enough to kill the weed seeds). It is a natural source of nutrients. Disadvantages: Compost is heavy to move and may not be available at all times.

Sedge Peat

Sedge peat is the left over remains of sedges, marsh grasses, reeds, and cattails. It is usually reddish-brown in color.

Advantages: It is usually sold in plastic bags and inexpensive. Disadvantages: May have salt in it, has lower water-holding capacity than sphagnum peat, breaks down quickly making frequent repotting necessary, holds less air than other media, and contains no nutrients.

Sphagnum Peat This is peat that is only partially broken down. You can still see plant parts in it. Sphagnum peat is usually light tan to medium brown in color.

Advantages: This can be purchased in several package sizes. It has good water and fertilizer holding capacity. Disadvantages:: Sphagnum Peat is very acidic. It may be expensive depending on locality. Due to its slow growth, many consider this a nonrenewable resource. It is very difficult to rewet if the plant is allowed to dry out. It contains no nutrients.

Bark

Many of the available mixes today use partially composted bark, a readily renewable resource. The bark is screened to sort the different sizes out. The smallest sizes are used as seed starting mixes while the medium sized pieces are used in potting media. The largest pieces are used as landscape mulch.

Advantages: It is usually very inexpensive, is a renewable resource, provides air spaces so the roots can breathe, holds adequate moisture for the plants, and provides some nutrients as it slowly breaks down. Disadvantages: It will require a high nitrogen fertilizer due to decomposing factors. If shipped a long distance, it will be costly.

Coir

Coir is the ground up husks of coconuts, making it a renewable resource. It is sold in dry bricks that are softened with warm water before use. <

b>Advantages: Coir is a renewable resource. It is easily rewettable, does not decompose easily in mixes, and is lightweight. Disadvantages: Coir often contains a high salt level and must be thoroughly leached before use. It is not available in all areas at this time. It provides no nutrients.

Vermiculite

Vermiculite is a silicate mineral that consists of thin plates similar to mica. It is heated to a high temperature, which causes it to expand into an accordion-like particle. Vermiculite is light tan in color.

Advantages: It holds water and fertilizer, allows the roots to breathe, and is lightweight. Disadvantages: It packs down over tine thus reducing the water and air retention levels of the media. It may hold too much water for some plants.

Calcined Clay

Calcined clay is baked clay particles. Terragreen™ and Turface™ are two common brands. It is frequently sold as a soil additive.

Advantages: This media holds water and nutrients from fertilizing. It doesn't break down in media and provides continuous aeration for the roots. It is also very lightweight. Disadvantages: Calcined clay can be hard to locate in some local garden centers and is usually available only during gardening season.

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