I had posted this in the SEEDS petunia forum...

"Last year, I filled some cells with about 3/4 PromixBX and topped with 1/4 seed starter mix (which is so much finer and lighter). My reasoning being the tiny seeds come up in the finer mix easier, but then would have the heavier mix to root into. The intention was to be able to leave them in the 6 packs longer. Seemed they had to be transplanted from starter mix to Promix at some point. I was trying to buy time and in some cases eliminate doing that step all together...Does that make ANY sense?...Anybody have thoughts/comments?"

Today I saw this post in another cubit...hmmm...
http://cubits.org/planthaven/t...

My thought? Don't need the seed starter mix at all. They germinate well in regular old potting mix .

Karen

I have been using the method described by Peter Thompson in his book Creative Propagation for about half of my indoor seed starting. He reccomends potting mmix covered by perlite for fine seeds and watering from the top to settle the seeds. Do not tamp the seeds in. He says that tamping the seeds in causes the soil to lose air and get packed down. I have tried it with some very fine seeds and it is working for me I am amazed to see those tiny , tiny seeds (portulaca for one) find there way to the potting soil. I settle mine in by using a spray all bottle .

I am trying coir this year... and always use a strong spray bottle as well

I don't like the coir at all. It has zip-o for nutritional value. I had seeded wax begonias and they all germinated fine and then just didn't grow. I started to fertilize it and managed to save a few seedlings.

Chocolatemoose, I like your idea of layering the mixes. I think I'm going to try it with some vines that I will seed in larger pots. I don't think it would be easy to do with the little 1" cells

i have always started my seeds in a typical seed starting mixandthen repotting them into a containe with MG potting soil for containers. next year i am eliminating the seed staring mix and planting the seedsright into the MG soil.

I found the Premier PGX too fine. Next year I will atick with Premier Promix BX for everthing

I like it too, Joanne. I never use seed starting mix any more. I just regular potting mix for seed starting and I like it better.

Karen

Not bothering with the starter mix next year either...ProMix BX for all...

BTW...Hi!

barbara - hi to you

i forgot to mentin that last year i experimented with the potting soil to stary my seeds and i had no problem but i only used it on several seeds.

I read that capillary action doesn't work between two dissimilar layers of soil. The water "perches" on the first without draining into the lower layer.

If that top layer gets waterlogged due to poor drainage, nothing can germinate and roots will drown.

Perhaps a thin top layer (like 1/4" or less) quickly becomes 100% waterlogged and then drains out by simply overflowing. If it is thin enough, or coarse enough, air would still penetrate enough that seeds and roots get the oxygen they need.

I always use a very coarse mix now that guarantee4s aeration & drainage no matter how much I ov er-water. Of c ourse that is TOO coarse for fine seds that need light and need to stay on the surface. In that case, I sprinkle a very thin layer of vermiculite on top of the coarse mix so that petunia and lobellia seeds don't fall into deep dark crevices.

My hope is that the vermiculite is thin enough and "wicking enoguh" that it does establish a capillary coinnection to the coarse mix under it (whic h does have SOME fine fibers of bark and peat).

OMG!! I just put tons of seeds under lights using 3 inches of potting soil covered with about the same amount of Pro Mix. I stopped using the tiny seed starter flats because I usually run out of room when I transplant them to larger containers. Now they're all in the containers that they will grow in for a long while. I did this last year and got good results. I hope that I remember Rick's information and water them carefully

You use 6" of soil depth? Wow, you must go through a lot of soil!

Karen

I do, but it's not wasted. Whatever isn't necessary for the planting is recycled. Many of the pots go to our plant swaps in the Mid Atlantic group. We received such beautiful plants back that my recipients deserve a plant in a really good pot (so that they don't all need to be transferred right away. We take hundreds of plants to the swap, and get even more back.

Hopefully the two soil types are similar ENOUGH that they "connect" and form some capillary channels that allow enough drainage that the top 3" don't get so waterlogged that they go too anaerobic ("Hypoxic"). I like the words "hypoxic" and "hypoxia" because they remind me that lack of oxygen is "toxic".

Also, I doubt that many garden containers get totally anaerobic - a pot would have to be pretty deep and clayey, or totally waterlogged, to allow NO oxygen to penetrate. "Anaerobic" and "anoxic" mean "NO oxygen".

Maybe, if you do add any more water, even misting the surface, do it with dilute hydrogen peroxide. That releases oxygen into the soil. Dilute 3% H2O2 1:32, like 1 Oz per Quart or 1.5 tsp per cup.

Also, consider bottom-watering the bottom 3" layer, and only misting the top 3" layer.

Seed flats are most at risk because they don't have big active root balls able to suck water out of waterlogged soil and transpire it out their leaves.

Also, shallow flats are more vulnerable to perched water because they are so shallow that a perched layer 1-2" tall may be the entire root zone.

>> I hope that I remember Rick's information and water them carefully

I'm not sure how to remedy it if the top layer is already water-logged. Keep it on a heat mat and run a fan, so it evaporates faster? Carefully poke little slips of cotton flannel or cotton butcher's twine down the side of each cell 4" to 6" deep to wick water from top layer to cotton, then from cotton to bottom layer.

Al (Tapla) pointed out that you can squeeze out SOME perched water by tapping the pot or tray on a hard surface. The inertia of the water causes it to try to keep moving down when the tray goes 'thump'. I imagine that the damp soil also compresses slightly and squeezes a tiny amount of water out. I can also imagine flinging muddy soil all over the kitchen table! I've tried this and gotten some water out the bottom, and some soil out of the top.

P.S. If you had one big flat instead of many small cells, you could remove the perched layer by tilting the flat so that one corner was several inches lower than the other corner. All the perched water would flow into the lower corner and "overflow" into the lower layer, since any given soil mix will only support a certain small depth of perched water layer. Or stir the soil in that corner enough to mix the layers. That establishes a capillary channel that will drain the entire top l;ayer into the bottom layer and eventually out of the tray through bottom holes.

You can dry out the BOTTOM layer of all perched water by placing the tray or pot on top of a terrycloth towel or cotton flannel. If the terrycloth touches the soil mix through the holes, it will establish a capillary connection and wick water out of the soil until the towel is soaked.

You can keep the cotton towel cleaner if you lay absorbent paper towels over the fabric. But the paper towel has to touch soil through the holes in the tray.

If you need to wick a LOT of water out, or, like me, want continuous protection against obsessive overwatering or excess rain, set the tray on top of a cotton flannel pad, and lay a long wick of cotton flannel under the pad and let it dangle DOWN a foot or so lower than the tray. The pad will wick water out of the tray through capillary action, then the dangling wick will drain the water out of the pad, through capillary action PLUS gravity.

Next year, you could have the advantages of two soil layers without that capillary-gap / two-perched-layer problem by letting the two soil types intermingle a litlte. Drop in the bottom layer but don't smooth or tamp it. Add around 1" of the top soil type, and stir each cell just a little, SHALLOWLY, so the top 2" intermingle somewhat. Then add the last 2". Now the transition should be gradual enough that the two layers are connected by enough capillary channels.that the top layer won't have its own perc hed water table.


I wish I could master the art of not over-watering! Up to now, I've treated seed flats (cells) the same way I treat big containers: top-water until water comes out the bottom, "so that salts don't build up".

DUHH! The two situations are totally different. Big containers are watered and fertilized for months or years, but I guess that if you "prick out" small seedlings with just a few leaves and one thread-like root, you never need to water it again after the initial dampening.

No need for multiple kinds of soil. Plain old potting mix works fine. The KISS principle applies.

Karen

Thanks for the reminder Karen! (KISS)

I think I have been starting seeds for about 45 years now.I've started tiny ones like begonias &lisianthus as well as the larger ones.I usually use the topping over Miracle Grow or my own mixture.I found seeds did not grow well in just seed starter.,probably because I failed to fertilize soon enough.I wouldn't be afraid to sow in plain ole Miracle grow but I have bags of starter purchased at a sale.I have never had a problem with watering the seed starter over growing on soil.I might use something as small as a plastic dip container for 200 petunia seeds(non pellets). Cream cheese containers just right for petunia pellets.I sow my tomatoes in a Ready Whip container. I like the larger size so I can grow them longer before transplanting to 8oz styro cups.I like to space my tomato seeds a half inch apart with a dampened toothpick.Same for pelleted seeds.By using these small containers I can set several on heat mat or under lights. Quite a few will fit in cake pan or plastic box & I put in greenhouse in sun.in the morning. Bring back under lights to extend daylight.at sundown.Lots of messing around I suppose but I like to tend to plants.It works for me because I am home.You use whatever medium that you have available & have had success with.I don't as a rule have failures unless I get careless.Stuff happens.
sewNsow

Rick, I actually do mess around with the first part of the pro mix that I add to the potting soil and then I just add more promix. Does hydrogen peroxide help anaerobic soil. Once I was using a large plastic container to wet my potting soil in. I didn't use it right away and, for convenience drained water from another source into it. After a few days, the odor told me it was anaerobic. It was quite a bit of potting soil, so I decided to hit it with some H2O2. A day later the soil smelled very fresh again. Is this soil now usable??