Saturday, February 18, 2012

Sterilizing Potting Soil

I realize I started My Alaska Garden blog last year and then neglected to post. I am hoping to change that as I would like to connect with other gardeners. I have so much to learn.


It’s +25*, my greenhouse is still buried under the winter snow, but the sun is starting to shine on my side of the hill in my corner of the world. Must mean it is time (or past time) to think about gardening.

greenhouse under snow

Last Fall my sons, Nick and Elijah, packed in some dirt I had stock piled. They filled three 55-gallon drums. This particular drum has a little dirt from a couple of house plants hence the white you see. I am making my own potting soil and so far, it isn’t all it’s cracked up to be. Two years ago I purchased it by the bags and spent around $350. Last year I mixed my own, but I was cheap. I didn’t mix in enough perlite or peat moss, the soil was too dense and many seedlings (like in the hundreds) didn’t make it.


This year I am mixing one part soil, two parts perlite…


and two parts peat moss. I can already tell the difference.

peat moss

This reminds me of the potting soil I used to purchase. I’m not so sure I’m really saving any money as the perlite was 4 cubic feet for $34.95 and the peat moss was 3.8 cubic feet for $44.95 plus the soil I purchased last summer (I think it was $65 a truck load so these three drums aren’t that much of the total price). If I keep the cost under $200 then it will be worth it. I go over that then my time probably isn’t worth it (unless I would have started the sterilization process earlier in the winter).

mixing potting soil

My first sterilization method was in the oven. I read several sites and decided to follow this one and to give it a try. Nowhere near efficient for the amounts I need. The damp soil was placed on a cookie sheet, covered in foil and put in at 180*. Once the soil gets to 180* it should be kept there for 30-minutes. It’s been over an hour and I’m only at 140*. This is entirely too time consuming.

sterlizing potting soil 1

I am now using the boiling water method. I am pouring boiling water through the mixture a total of three times. Once it cools then I can plant.

sterlizing potting soil 2

Here are some 6-packs of Impatiens because I am impatient! I’ve already planted some geraniums and need to plant for the greenhouse, but since I don’t have those seeds I planted the Impatiens early!

filling 6-packs

I cover with fine soil or vermiculite, cover with a plastic dome and put under the lights. I will quickly run out of domes as I only have about 12 and they are $3.00 each! When I do, I’ll cover the flat in saran wrap.

planted; topped with vermiculite

I’m so excited for the “beginning” of gardening season in Alaska.

1 comment:

ChrisC said...

I've tried making my own potting soil,but I'm too lazy.Somewhere I have the recipes for different potting mixes.If I can find them,I'll e-mail them to you.