I have used vermiculite as part of my mixes for both onions and leeks for a few years now and I find that I have quicker growth, probably as a result of a stronger root system as more air is able to get into the compost. My sowing mix is three parts F1 and one part vermiculite thoroughly mixed together. Also there is no doubt at all in my mind that vermiculite is best to cover the seed over in preference to the same compost in which they are growing.
Home - Vermiculite as part of Mixes and for Covering
Medwyn Williams
Hello. I'm Medwyn Williams – eleven times Gold medal winner at the Chelsea Flower Show, Past Chairman of the Royal Horticultural Society Fruit Vegetable and Herb Committee and President of the National Vegetable Society.