Maybe I saved a bag of peaty Miracle-Gro seed start mix too long, or abused it during storage, or something. My bag was like a bag of peat dust, and it would have retained too much water and zero air even if I was not an over-watering idiot.
As far as being gritty or well-aerated - once wet it was like pudding.
Around the same time I wised up to TRYing to overwater less, I also started making much coarser seed-start mixes using screened bark shreds and ProMix-like "professional" soilless mix. And sometimes a little crushed stone or the coarsest sand I can find.
And then I added the wrinkle of a layer of cotton flannel under my propagation trays.
(Absorbent felt should work as well, or an old towel or Tee shirt.)
Now, I can "bottom water" without clogging my bathtub's drain with mud, bark and grit.
The absorbent pad sucks any perched water right out of the prop cells, and re-directs it to any extra-dry cell.
And holds enough water to supply every cell for 1-2 days.
http://garden.org/ideas/view/R...
I no longer kill tray after tray of seedlings. But is it the coarse mix, the cotton flannel, or TRYING to do less over-watering?
