Homemade Seed starting mix

Anyone making seed starting mixes from local ingredients? I live in upstate NY and would like to find a successful alternative to the standard peat moss, perlite, vermiculite mixes. I've read a bit about using pine bark (other types of bark too?), sand, compost, soil (sterilized), but I know the big issue is that the mix needs to hold moisture and air, while not compacting.
Thanks,
Paul

I like pine bark, fir bark or hemlock bark.

I'll buy some good-quality professional potting mix like Fafard, Sunshine or Pro-Mix, but mix in lots of screened bark shreds and nuggets to open it up. When I say "lots", I mean 60-80% screened bark and 20-40% Pro-Mix.

Plain bark (not orchid bark) is MUCH cheaper than good potting mix. It's even cheaper than crummy, no-air peaty mixes from Home Depot. I never figured out how to keep those peat-powder-potting-mixes from becoming totally waterlogged and anaerobic.

I've been told "just don't overwater them", but have never mastered that skill. Instead i make the seedling mix drain well enough that excess water drains AWAY and lets air in. Coarse additions to crummy MG "peaty powder" make it almost adequate. Adding bark shreds to a GOOD potting mix make it GREAT potting mix (and can cut the price by half or more). My idea of a GREAT potting mix or seedling mix is one where the roots CAN'T be drowned by a Bozo with an over-active watering gene.

I think the best sizes of screened bark to "open up" peaty mixes are like coarse Perlite, and larger (say 1/10th inch or 1/8"). Larger than BBs, smaller than big peas, maybe smaller than baby peas.

If I can get long shreds or chips, that's better for aeration than rounded nuggets.

Bark that is much smaller than 1/10th inch holds water, and should be thought of as a [u]replacement[/u] for peat, not a way to open it up and make it more airy.

"Mulch" from big bag stores is often dirty logyard trash. Where I live, Lowes has much cleaner products than Home depot, for similar prices.

The cleanest I found around $4 per 2 cubic feet was "Small Pine Bark NUGGETS". Most of those are bigger than I want in seed-starting mix, but I can use the coarse stuff as mulch, or chop it with an electric lawnmower.

The most important thing is to screen or winnow out all the dust and fine fibers in the bagged bark product. Fine bark fines (say, much smaller than 2 mm) are only a little better than peat - it will retain too much water and pack together too tightly to let air in.

After you screen out the fines or blow them away, the fines are a great addition to raised bed soil. If you have clay soil, they won't make the aeration any worse, but they will "soften" the clay and make each little clay ball less sticky to its neighbors.

Paul - I think the main concern would be a) malevolent organisms coming in on pine bark and compost and b) soil being rather heavy for seed germination. I think John Innes (UK) makes a few different types of seed starting mixes and I even saw a recipe for a compost-based mix. You might want to check out that website and see if you have the ingredients locally.

Old gardening books from England seemed to call all seedling mixes "compost".

I never knew whether they started seeds in pure compost (recently-decomposed vegetable matter) or just had a funny name for any peat-rich, light, open water-holding mix.

Compost from a compost heap is kind of the opposite of "sterile, soilless mix", which most people now seem to recommend for starting seeds.

I've often wondered if you could count on beneficial micro-organisms from a compost heap protecting against plant pathogens on seedlings.

People do make compost tea to spray on mature plants' leaves and on soil "to add beneficial organisms".

Rick - I think you might be right about the Engish definition of "compost" but I am curious about it now. I do watch some English gardening shows via Youtube and they seem to use a coarser yard-waste compost for outdoor soil amendments than we're used to seeing/hearing here in the states. Perhaps the key is to start with a light, soil-free mix and then pot up as soon as possible into amended potting soil? Doesn't help Paul though. Keeping it simple, any combination of sand/perlite/vermiculite should work just to get the seeds started. Perlite and vermiculite do have some level of moisture retention but I'm usually hovering over seedlings every day to make sure they don't get too dry.

>> Keeping it simple, any combination of sand/perlite/vermiculite should work just to get the seeds started

I guess I have always used something with a lot of fibers - either peat which I now dislike, or pine bark fines that I didn't screen as carefully as I wish I had (to get rid of dust, powder and fine fines).

Thus my mixes start out too heavy and dense (not light, not well-aerated or well-draining). Thus I add a lot of COARSE amendments.

For me, any sand is too fine but grit is good. Coarse Perlite is good, but expensive. The very coarsest vermiculite might be good for lightening fine peat, but I've never found coarse vermiculite except in super-expensive small bags.

I like bark, screened to be a gritty size, up to BB-size if it is the main ingredient, or up to 3/16" (0.2" or 5 mm) if it is a coarse amendment for a mix that is much too fine-grained. But you have to get rid of the FINE bark dust and fibers, or it won't be an airy mix, and will be prone to water-logging when over-watered.

I have to say "WHEN overwatered", not "IF overwatered". I haven't fully learned how to avoid over-watering.

I've limited access to sand specifically for potting soil. I did pick up a bag of traction sand last week - a little coarser than coarse builders sand - and hoping that will leave some air pockets when mixed with compost. Just hope the traction sand doesn't have questionable origins.

Maybe you could screen your compost to remove as much fine stuff as practical while keeping anything fibrous, chunky or gritty.

Went around last week looking for bagged compost but garden centers don't cater much to those of us who don't only "garden" in warm weather. I have one bag of soggy mushroom compost, another unbranded bag of mushroom compost mixed with peat (maybe I should reserve that one for garden use) and a small amount of too-wet worm compost. Sigh. I'm wanting to repot my lemon tree before it goes back outside and wanted to try a mix of sand and compost instead of a peat-based mix since it has a hard time growing new leaves although it will fruit just fine. And I don't use bark mulch here - only shredded leaves that are frozen solid at the moment.