fertilizing WS containers & H2O2 solution

I wanted to report on some things I tried. Somewhere in DG I read a long thread about using dilute H2O2 to improve O2 uptake in the roots. So I tried some dilute solution on my WS containers - which by the way, some of them are WAY too shallow - first ones I did in Feb. In identical pans, Sweet Williams sprang to life and started working on their first set of true leaves even though I haven't thinned yet - and about half a pan of red perennial Poppies turned brown and died. My dahlia seedlings sat up and grew another inch taller in 4 days, but the purple basil and sweet basil looks like it got an extra dose of something nasty it didn't like. The marigolds, Alaska Shasta and Centaurea 'Black Ball' didn't like it either, but the delphiniums, nepeta and cilantro greened up with it

I haven't fertilized any of my seedlings in the containers, but I planted out Delphinium Pacific Giant - tiny seedlings on Friday and watered with Liquinox rooting starter. Tonight the ones that had some shade looked great, but some that had too much sun were a bit wilted.

I am perplexed why my seedlings don't seem to have grown in the containers unless its because they are just so crowded. But even the ones that aren't crowded aren't doing much. My deck is cool and above ground - could it be that the soil and air temps aren't high enough yet?

Are any of you fertilizing in containers before you plant out?
Thanks!

I do, because I use potting mix which has no ferts in it. Once I have sprouts, depending on the plant type, I start watering with a very dilute compost tea.

Interesting report, alyrics--thanks.

I soaked my seeds in H2O2 before planting and in general now feel it was overkill to do that--I got plenty of germination but I think I would have gotten the same anyway (not very scientific conclusion, is it?!!) LOL Just instinct, I guess. So I won't soak seeds again, unless it's a 'hard to germinate' seed type.

No, I haven't watered with H202, but maybe I will! And I will let you know the results. To bad some of your seedlings 'bought the farm' so to speak.

I planted my seeds in 'Miracle Gro Potting Soil with Moisture Control' which has fertilizer in it. I am not sure if this was the best choice for planting medium, but it seemed to work OK for me. I think next year I will try to lighten it up with some peat or something similar and also try to add some less expensive ingredient to stay on budget. On the Soils Forum some threads had recipes for making your own potting soil, and I may try one of those next year and add Osmocote when the seedlings get their true leaves.

I did give my seedlings a dose of 'Superthrive' which is new to me. But I do think they liked it. I think many DGers are trying 'Messenger' this year and I'm going to get some of that, too.

I am a little surprised at how small my seedlings are too (compared to the garden center) but mine are in a part shade spot, too. And on the north side of the house, so cooler, also.

Would like to hear about more H2O2 results....?

donn, if your seedlings are small, mine are minuscule!