Seedling flat growing medium
Every year when I start getting ready to grow seedlings I mix up a batch of seedling flat growing medium. By starting with new growing medium every year I ensure there are no insects, plant disease or weed seeds. This helps to ensure healthier plants are going into my garden and I am not introducing weed seeds to the garden.
How to mix custom soil
Time to mix up the sawdust, sand and perlite that will be used as our growing medium in our seedling flats. We mixed 2 parts sawdust, 1 parts sand and 1/2 part perlite for our seedling flat, as seen in the pictures below. The perlite is optional and can be omitted to keep your costs down.
The Mittleider Gardening Course book recommends 3 parts sawdust to 1 part sand. It also gives options to sand and sawdust, including mixing ratios. Get your own MGC book here if you don’t already have one.
Seedling flats are shown in the Mittleider Gardening Course book on page 181. The dimensions of the seedling flats are 18″ x 18″ x 2 1/2″. Once filled with the mixed growing medium we added 1 1/2 ounces of our pre plant fertilizer mix. (Page 51 in the MGM, revision 4)
Do you prefer to use your own soil?
Not everyone wants to mess with the extra work of acquiring everything to make a custom growing medium. The correct sawdust can be difficult to find and even expensive when you do find it. You can sterilize your own soil and grow healthy seedlings. See my blog post on Seedling Success Through Sterilized Soil.