March is the perfect time to start seeding in six packs and flats. For best results make sure your pots, flats or six packs are clean–if you are reusing last years six packs, wash them in hot soapy water before planting. Seeds will start best in a fine absorbent medium that gets good drainage. Pre-mixed seed mediums are expensive and it is so easy to mix your own.
Here’s how: 3 parts fine coconut coir, 1 part perlite, 1 part worm castings.
Traditionally peat moss was used rather than coconut coir. But peat moss is non-renewable while coconut coir is a product rescued from the waste stream. It is available from many local nurseries and also online. Be sure to get the fine grade–it also comes chopped coarsely and in that form is an excellent mulch. Cocnut coir is the part of the mixture that holds and absorbs moisture so your wee seeds won’t dry out. Perlite, also available at nurseries is a volcanite glass. It helps with permeability and drainage in the mixture. If you wanted you could just mix these two together 3:1 or so. But you would need to start fertilizing your seedlings with a balanced dilute fertilizer once they have their first leaves as neither cocnut coir nor perlite contains any nutrients. Another option is to add one part worm castings or well aged compost to the mixture. There is some danger of introducing pathgens by this method, however it also greatly increases the seedlings strength and immune system.