Peat (sphagnum peat moss) is the slowly decomposed remains of bog mosses, harvested from peatlands. It is light, very water-retentive, has a useful cation exchange capacity and is naturally acidic (raw pH about 3.5-4.5). Mixed with lime to raise the pH, plus perlite and fertiliser, it forms the base of most commercial potting mixes, including many sold as "soil".
In practice
Peat mixes work well for cannabis at a pH of about 6.0-6.5 in the root zone. When very dry, peat becomes hydrophobic and sheds water; rewet it slowly or with a wetting agent, and avoid letting it dry out fully. Mixes typically lose their starter fertiliser after two to four weeks.
Peat extraction releases stored carbon and destroys bog habitat; coco and composted bark are common alternatives where growers want to reduce peat use.
Don't confuse with
- Coco peat: coconut pith, sometimes called peat but a different material.
- Peat pellets: compressed peat discs for seeds and clones.
Cation exchange capacity (CEC) is a medium's ability to hold positively charged nutrients such as calcium, magnesium and potassium on its surfaces and release them later.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Perlite is a light, white, puffed volcanic glass added to growing mixes to increase drainage and air space; it is chemically inert and holds no nutrients.Potting mix is a manufactured container medium, usually peat or coco with perlite, lime and starter fertiliser, designed to drain and hold air better than garden soil.The root zone is the volume of medium or solution where a plant's roots live, including its water, air, temperature, pH, EC and microbes.The wet-dry cycle is the alternation between watering a container and letting it dry back, which refreshes oxygen in the root zone between irrigations.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.A soilless medium contains no mineral soil, such as peat, coco, rockwool or perlite blends, and relies mostly on the grower to supply nutrients.
