For seed starting, keep it
clean and simple. When looking for a suitable medium, first, to clarify, there’s potting soil, and potting mix, and
the terms are used interchangeably and not always accurately. Those brightly
coloured plastic bags with bragging labels can be confusing. The difference is
potting soil contains soil, often only a little, sometimes a lot. It’s more
suitable for use outdoors. There are, however, mixes specifically formulated for seed starting.
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Peat Moss
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Most products on the shelf
are potting mixes, sometimes referred to as soil-free. They can contain any
number of ingredients, with the usual claims for best results, but the
ingredients aren’t always on the label. They can contain coco coir, wood
fibers, peat moss, vermiculite, clay, pumice, or perlite. All have their uses, but
not all are essential for starting seeds. Seedling grow best in a
lightweight medium that provides a balance between moisture and air. Most potting
mixes are made up of finely shredded peat moss. Perlite is usually added to
improve drainage, and it also helps retain moisture. Perlite is a naturally
occurring siliceous volcanic rock that after processing looks like tiny bits of
popcorn.
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Perlite |
Cheaper, no-name brands might even contain tiny beads of polystyrene
as a perlite substitute (in my darker moments, I’ve often thought potting mixes
would be a handy way to dispose of industrial waste). Some mixes also contain vermiculite,
a spongy, gold coloured volcanic mineral added
to help retain moisture.
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Vermiculite |
Lime might be added to
neutralize the slightly acidic peat moss, and other ingredients may include wetting
agents to promote absorption of moisture, slow-release fertilizers, and
charcoal, which is a natural filter that absorbs decaying plant odours. The
problem with added fertilizer is you have no control over the amount, and since
we all use our preferred fertilizers as well, there’s a danger of over-fertilizing. I prefer to be in control.For seed starting, keep it clean
and simple, and I'd avoid the $1.99 bags from that other store.
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