Peat Pots are a favorite biodegradable way to start seeds indoors. When it's time to transplant, set pot and all into the soil, the roots will grow right through the peat pot walls, permitting replanting without removing the pot. No shock or setback is suffered, so faster, heavier growth takes place. Peat Pots are made of peat, wood fiber and soluble fertilizer. The perfect choice for most seedlings.
There are two basic peat pots compositions. Jiffy pots [trademark of Jiffy Group] contains a peat based mixture enclosed in a nylon mesh which basically holds the peat mix in place. In most cases it is a good idea to remove the mesh before planting. The second is composed of minute fibrous peat and additives that you add your own potting mix to. Peat pots are of course more environmentally sound than conventional plastic, clay or ceramic pots and generally require less labor and sustain less plant damage upon transplant.
Peat Pellets expand when watered, creating a natural seedling pot made of peat. The pellets also contain a minor fertilizer charge plus lime to balance the acidity of peat moss. Manufacturers claim that the roots will grow through the pot and anchor in the soil, unfortunately this is not always the case. The larger roots will push through, but if the pot does not break down rapidly enough quite frequently the smaller roots become confined, the end result being suffocation of the root ball and stunted growth.
Another common complaint against the peat pots and pellets is that they do not retain water as well as would be liked. They are either too dry or completely water logged with no happy medium.