Yes I have been to Alplains, and have some plants from them.
I had really great germination on Penstemon pinifolius and purple specie cross penstemon. Left the seed heads on the plants over winter. Seedlings everywhere in the beds late spring.

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.

rcorey: -I tried bulk coir

>> coir have changed dramatically in the last ten years.
>> nature's footprint. just don't buy the cheapest stuff and try to find reviews. hydroponics people use it - so pays to read the forums.

>> coir peat does not compact even when wet, so aeration is much better then with reg peat. and it does not turn into mush in 1 season like peat either. i actually read that it could be reused - like it gets better as it ages ;), so long as it does not have pathogens and dead rotting roots in it. try shaking it off the roots - and you'll see it's possible. i reuse mine from succulents when i repot them into new mix. and by the way all cacti/succs come in coir peat now ;).

That's really good to know! I'll try it again and skip checking HD. That loft, aeration, and durability are why I went from peat moss to bark fibers. It sounds like coir is the same idea only much better. Most of the cheap coir bricks I tried had enough powder and small fines that they would not have held air even when drained overnight.

BTW, CarolineScott, who re-uses potting mix, described flushing it with good compost tea to displace old soil microbes and establish beneficial new ones. Great idea!

The thread "Rejuvenating soil in containers" in Containers forum

well, i won't really advocate reusing the potting mix as a whole, unless it was in the isolated 'clean' pot and free of disease. then adding humus and extra bark or perlite should be ok. i've done that for like petunias or pansies, smth not demanding and disposable. the rest can go into compost pile (which of course i don't have in the city).
but, of course, i'm mostly indoors gardener and put a lot of my indoors plants on the balcony just for summer. so they stand mixed up with permanently outside pots - and can get contaminated with some eggs/larvae - so i have to be very careful with my mixes and up-keep.
i deff reuse scoria after rinsing - it takes 5-7 years for it to fall apart and it has nutrients too.
and you can 'disinfect' the bark by pouring lots of boiling water thru it.
i mean, i agree that some large seeds will germinate well in moist bark. just not small seeds.
google 'mesh seed trays' or 'netted seed trays' - i think those will be just right, turn them upside down and drape wicking mat on top. and then they have to go into 'water trays' and your seed-trays on top. kinda elaborate. some hydro-tray set-ups might be easier.
when i started with my suggestions i did not realize you have a large 'production' going on.
i do very few seeds. only smth special. i sprouted zamia furfuracea and lignum vitea just for fun, with a heating pad and moist perlite under dome (zamia took 4 months!). will see if they can survive the winter. but it's fun.

Hmm! I wouldn't have thought those mesh-bottom trays could support any weight at all without sagging. But with some kind of supports under them ... that might just the thing. Thanks!

Up to now I haven't used cap mats to water seed starting trays for multiple days unattended. Just the opposite, I lay the mat and seed trays right flat against the bottom of the water-holding tray. It's there to help me avoid over-watering. Next year, with a better-wicking seed mix, maybe I can reduce my top-watering to just once every week or so.

>> i mean, i agree that some large seeds will germinate well in moist bark. just not small seeds.

I just assumed that my petunia seeds all died because they fell into gaping cracks in the surface. Maybe the deeper parts of the cell would have been too coarse even if I had put a layer of vermiculite on top for tiny seeds to sit on. I would experiment, but I'm already leaning toward somewhat less coarse bark/commercial mixes for seed starting (to get more wicking up from my mats).

I think I'll always aim for a coarser seed mix than most people choose, because aeration seems so important to me, and I don't mind top-watering or misting twice per day if necessary. If very small seeds just can't handle that, I'll have to adapt. i THINK I started Lobellia that way one year, with a very coarse bark mix, and thought I had fine germination. Of course, with dust-like seeds, maybe I sowed three times as many as I thought I did, and the germination was terrible!

BTW, an idea you suggested like stuffing a small wick into the bottom slit of each tray sounds better to me when I picture short lengths of bulky yarn. If it's necessary for good contact, that would be fairly easy.

>> i did not realize you have a large 'production' going on.

In Springs when I DO get busy with seed starting, I usually have four trays going, either starting seeds or potting up seedlings. If I get any kind of cold frame structure built, I hope to increase that.