LO 5.5 - Potting mixes Flashcards
- Potting materials, their advantages and disadvantages e.g. peat, coir, bark, sand, soil, perlite and vermiculite - Mix ratios - John Innes type mixes
Question
What are some advantages of potting mixes over soil?
Potting mixes
- Other growing media tend to be more uniform in terms of structure and texture, nutrient content and pH.
- In pots, ordinary soil is inclined to become compacted due to the lack of earthworms and insects.
Potting mixes
Question
How many different types of potting mixes can you name?
From a list of nine.
Potting mixes
Different types of potting mixes
* Peat
* Bark
* Coir
* Composted green waste
* Perlite
* Vermiculite
* Rockwool
* John Innes Composts
* Hydroponics
Potting mixes
Question
What are the advantages of Peat?
Potting mixes
Advantages of Peat
* Almost sterile, and relatively free from pests, disease and weed seeds.
* Peat contains almost no nutrients.
* Light, clean and not unpleasant to handle.
* Peat has a high water-holding capacity.
Potting mixes
Info
Sphagnum moss peat is the most commonly used horticultural peat.
Potting mixes
- It is naturally acidic so lime is normally added.
- Pots are ‘loose-filled’ to maintain air spaces.
- Peat can become hydrophobic if let dry out.
Potting mixes
Info
Bark some important info
Potting mixes
Bark
* Typically conifer bark. Normally the waste products of fencing and timber industries.
* Chipped and matured in heaps. The material is then screened and the larger particles are recycled into the next batch of heaps.
* Often contains a certain amount of white wood from the timber which can make the product ‘stringy’.
* Needs to be well composted/screened for nursery use; this is less critical for use as a landscape mulch.
Potting mixes
Info
Coir is a product produced from the outer husks of coconuts. It has been used in growing media since Victorian times.
What are some benefits of Coir?
Potting mixes
Coir
* The particle size is very uniform so it has a well defined pore size distribution.
* The air filled porosity (AFP) of coir ranges from 24 – 30%, so it is useful in conditions of high humidity where waterlogging must be avoided.
Potting mixes
Info
What are some disadvantages of Coir?
Potting mixes
Coir disadavantage.
The major disadvantage of coir is its inability to hold nutrients – this can be overcome by adding clay minerals.
Potting mixes
Info
What are the available grades of Coir?
Potting mixes
Coir grades.
* Pith/dust is very fine, suitable for germinating seeds but can be poorly aerated. Good water holding.
* Coarser fibres or chips drain better and give better aeration.
* Also available in blocks or sheets.
Potting mixes
Info
What are advantages of composted green waste?
Potting mixes
Composted green waste.
* Good source of potassium and micronutrients
* Good water holding
* Sustainable
* Variable source materials – quality control important
*Note: May contain pathogens, herbicides and etc…
Potting mixes
Info
Can you describe what Vermiculite is?
Potting mixes
- A naturally occurring mineral that is formed in sheet-like plates. When heated it exfoliates, forming concertina-like compressible particles.
- Like clays, vermiculite has a large surface area relative to its volume and thus a high cation exchange capacity and buffering capacity. Used at 5-15%
- Also improves aeration and water-holding.
- Often used as a seed covering – lightweight, maintains humidity around seeds, not dense enough to exclude all light.
Potting mixes
Info
Can you describe what Rockwool is?
Potting mixes
Rockwool
* Rocks (basalt, dolomite) melted at high temperature to form molten matrix, air stream cools the material and forms long fibrous strands.
* Good aeration, light, clean.
* Used in the form of cubes or sheets, or shredded and mixed with other materials.
Potting mixes
