Horticulture Growing Medium

Types of Organic Media A – Sphagnum Peat Moss 1 – the remains of dead plant materials harvested from peat bogs 2 – 1/25th of an inch of compressed moss equals one year of growth 3 – Most is imported from Canada. (only 5% of worlds supply is in the U.S.)

5 – very high in pore space 4 – very high water holding capacity makes it important for horticultural use a – weighs 6 ½ lbs. per cu. ft. when dry b – weighs approx. 100 lbs when saturated c – can hold 15 to 20 times their weight in water 5 – very high in pore space

B – Sawdust 1 – replacing peat in some areas 2 – certain trees contain harmful substances (walnut and ceder) 3 – bacteria that decompose sawdust rob the soil of nitrogen

C – Sand 1 – deep-mined white mountain sands are mainly silica 2 – free of diseases, seeds, and insects 3 – increases porosity

1 – volcanic rock mined as an ore D – Perlite 1 – volcanic rock mined as an ore 2 – heated particles expand like popcorn 3 – pH of 7.0 to 7.5 4 – improved aeration and drainage 5 – is dusty and does float

1 – Mica-type mineral expanded by heating E – Vermiculite 1 – Mica-type mineral expanded by heating 2 – flat plate-like mineral expands like an accordion but can be destroyed 3 – holds 500% water by weight 4 – high in potassium, magnesium, and calcium

F – Coconut Coir 1 – made of the outside shell from coconuts 2 – increases aeration and drainage

II – Composition of the Growing Media A – Solid material 1 – approx. 50% 2 – organic or inorganic depending on soil type B – Liquid 1 – approx. 25% 2 – too much water and plants become “water-logged”, causing fungus or fertility problems

C – Air space 1 – approx. 25% 2 – too much and soils cannot hold water 3 – too little causes restriction to rooting

III – Advantages of Soil-less Media over topsoil A – consists of material with known properties B – typically more consistent C – easier to handle and mix

D – fertilizers and pH can be adjusted to desired levels E – correct drainage and water-holding capacity are adjusted F – sterilization is generally not required G – cheaper to prepare

IV – Soil Moisture A – Three forms of water 1 - Gravitational Water – temporary and drains from a soil by gravity 2 – Hygroscopic Water – mostly in vapor form and unavailable to plants 3 – Capillary Water – water held between soil particles by capillary action

B – Field Capacity – the amount of capillary water that is available to plants after gravitational water has drained C – Wilting Point – the amount of water present when plant starts to wilt; soil particles typically hold water with 15 atmospheric bars of pressure