Rootrainers provide the best growing system for seeds plugs & cuttings by way of the deep ribbed cells which help seedlings develop strong fibrous root systems. The unique open-bottomed design of the cells allow earlier root tips to make contact with the air & die off which are replaced by fresh young roots. The re-usable cells hinge open to allow easy removal of the plant with no root disturbance ready for transplanting. As recommended on BBC Gardeners World Friday 20th April 2007