I think we’re talking about 4-5 things at the same time! Maybe I’ll try to save some issues for next week.
You’re right, I’m mostly talking about seedling trays, and then speculated about 5 gallon buckets for tomatoes.
>> seeds need finer particle mix especially fine rooted ones - i never use bark in any form on those. bark by itself does not wick at all.
I do usually use seedling mixes that are much coarser than most people use. I only have 1-2 years experience with that coarse mix, but it works much better for me than my past practices (mostly peat, over-water, damp-off, soggy roots). Maybe finicky seeds do need a finer mix. And I am planning to try something finer and better-wicking
Also: I already have some bark fibers and even fines and even dust in my mix, along with around 20% commercial peaty mix. I do seem to have some wicking with that mix. Remember that in insert trays, water only needs to wick a few inches at most.
I lost a whole tray of petunias once because I left the surface coarse. The tiny seeds fell into cracks and never emerged. (Petunias need light to germinate.) Next year I would cover the surface with vermiculite so the tiny seeds don’t get lost.
>> if you're growing in med/large mostly bark mix you'll just have to top-water! and feed and flush - that is just the nature of the mix. it's labor and water and fertilizer intensive.
That sounds like one step more coarse than I’ve been using for seedlings, and I agree. Frequent watering and reduced wicking is a result of very open, very fast-draining mixes. When I took “very well aerated despite overwatering” as a goal, I accepted frequent watering as a cost. However, with my over-watering compulsion, frequent watering is not just acceptable, it’s fore-ordained.
“Learn to not overwater” would be good advice ... I’ve made some progress i that direction over 3-4 years ... I missed Dave’s podcast about “why don’t we do things we know we SHOULD do?”
>> are we talking like up to 4" pots for seedlings? or just lil'plugs?
I use very coarse, open mix for both. It seemed like a Godsend to me, because for once I started getting air all the way to the bottoms of tiny cells and small pots.
Maybe the take-away should be something like:
“For most gardeners who CAN avoid over-watering, a well-wicking peat-based mix is natural for seed-starting, tiny cells and small pots. Perlite is a popular, sterile way to “open up” peat moss so it remains aerated during moderate watering. Unconventional mixes can compensate for over-watering by making drainage so fast that water does not saturate or perch in any part of the cells. Screened pine bark in various sizes can be used to make such a fast draining mix, though not all bark is as clean as heat-treated orchid bark.”
>> besides it can harbor all kinds of spores and molds - that's just too risky.
Lord knows that “mulch” from HD is filthy! I do still have some screened fines from that batch several years ago. . Maybe I’ve just been lucky. Maybe my super-coarse mix protected me from “dirty microbes”. Maybe I mostly start very vigorous seeds and they just plow right through competing mold. But your point is very good for anyone working with rare, expensive or slow seeds.
