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Horticulture 1000
HT1031 - Soils 1 - Alternative growing media
Soil structure Soils 2
5

Alternative growing media

Growing media is what a plant is growing in. A good growing media provides:

  • ample drainage
  • air around plant roots
  • enough water for plants to use
  • nutrients
  • support for the plant so it can grow upright towards the light.

Seeds grown outside are usually sown in the soil, which is a natural growing media. When seedlings are grown in containers usually an artificial growing media is used.

Artificial growing media, for example potting mixes and seed raising mixes, are made up of a mixture of inorganic and organic materials. The table below shows the types and properties of different materials used in artificial media.

Remember:

  • organic is or has been alive.
  • inorganic has never been a living organism.

Artificial growing media:

                                                                                   
MaterialTypeProperties
Peat
  Peat
Organic Holds water and minerals. Has good drainage and aeration.
      Reasonably free of pests and diseases.
      Expensive.
      Lightweight.
      Needs to be wet before use.
      Keeps good structure.
Shredded bark
    Shredded bark
Organic Holds water well.
      Good drainage and aeration.
      Reasonably free of pests and diseases.
      Cheap and readily available.
      Heavy to carry.
      Needs to be wet before use.
Sand:
      river, builder’s or washed beach sand
  Sand
Inorganic Good drainage and aeration.
      Free from pests and diseases.
      Cheap.
      Heavy to carry.
Medium grade pumice
  Pumice
Inorganic Good drainage and aeration.
      Reasonably free of pests and diseases.
      Readily available in the North Island where it is cheap.
      More expensive in the South Island.
Perlite heated lava flakes
  Perlite
      Vermiculite heated rock flake
      Vermiculite
Inorganic Holds water well.
      Good drainage and aeration.
      Reasonably free of pests and diseases.
      Very expensive.
      Lightweight.
Fast- and slow-release fertilisers
  Fast- and slow-release fertilisers
Inorganic Fast-release fertilisers add nutrients to the mix quickly.
      Slow-release fertilisers stay in the media and release their nutrients    slowly over several months.
      Fertilisers can be added later during crop growth in the form of    liquid fertilisers if needed.

There are different artificial media or mixes for different purposes.  For example:

  • seed raising mixes don’t require many nutrients, as the seedlings are pricked out early in development
  • cacti and succulent mixes need lots of pumice or river sand for extra free drainage
  • orchid mixes need lots of coarse bark material for good root development and aeration around the root system
  • acid-loving plants such as azaleas, daphne and rhododendrons shouldn’t have lime added to the mix
  • most general mixes would be made up of 50% inorganic and 50% organic material.

In this course use a general purpose potting media/mix for all your  container needs.

Key points   Key points

  • Growing media is what plants grow in.
  • A good growing media provides water, air, nutrients and support for plants.
  • Generally, an artificial media is used for container growing.
  • Seedlings in containers can be kept in a protected environment.

What's next?

  1. Complete the self-assessment in the back of your workbook HT1031. Return your workbook to your teacher.
  2. Continue with HT1032  Soils 2.
Soil structure Soils 2