1 part well-rotted compost (Fine compost). 1 part coarse sand (Malmesbury). 1 part Vermicompost (Homemade or bought).
1 part well-rotted compost. 1 part good garden soil (Loam). 1 part coarse sand (Malmesbury).
The compost absorbs and holds moisture. Sand provides drainage and will also prevent crusting on the surface. Vermicompost contains nutrients and also increases water holding capacity.
Please note when making a seedling mix that vermiculite and cocopeat can also be added to the mix in small amounts to increase water holding capacity, but do not add too much as it can affect drainage and cause seeds to rot rather than to germinate and grow.
The last step to making a seedling mix is to make sure that it is weed free (kill weed seeds), free of fungal spores, insect larvae and eggs. This is done by pouring boiling water over the filled seed trays, soaking them before sowing seeds. Make sure that the trays are on a level surface when doing this to make sure the water runs straight out of the bottom.