Way to go Chelle!

Those will be great next summer!

A question for you Vermiculite experts...

I called around and have found the Palmetto brand "Course A-3" grade available at one Feed & Seed store. It seems this is the grade that is popular for the Square Foot Gardening mix so that's likely why it's available. Is this the grade that would also work well for seed sowing? Another Feed & Seed store says they will have "Medium" and "Course" in by the end of the week (I'm not sure of the brand.) Any guess as to which is best for seed sowing? Unfortunately, you can't see through the bags to look at the size of the particles.

http://palmettovermiculite.com...

Thanks for any info!

I'm not familiar with that brand or designation, Danita, sorry, but I'd guess that anything designated with a 3 would be coarse, but not quite as big as large. Large-sized pieces might typically be used as "glowing embers" in a faux log stove, but would probably be a bit too big for finessing sprouts out of containers without damage.

Finer vermiculite can work too, but I think moisture levels have to be more precise when using the closed container system. I have sprouts in the fine stuff now, but when I remove the covers to check on those there is a disquieting odor to it. Not quite an odor of decay at present, but maybe a precursor of it. Whenever there's a choice involved, I'll use it for very short germination/duration type sowings, and get the seedlings out of it as soon as possible.

I'm growing more and more sure each time I buy it that I'll only trust what's inside if I open a bag and look.

I'm not familiar with it, either.

Karen

The "Red Bag" Coarse A-3 has a product sheet. If the "Square Foot" A-3 is the same size, this would tell the particle size:



Mostly 6 and 8 Sieve. What's an "8 Sieve"?

I think this is it:
No. 6 - - - - - 0.132 inch opening - - - - - - 3.36 mm opening - - - (bigger than 1/8")
No. 8 - - - - - 0.0937 inch opening - - - - - 2.38 mm opening - - - (smaller than 1/10")

That would be a good size for lots of air and little or no perched water, it seems to me!

(Edited to add - it would make a great amendment to "open up" a mix and make it more airy. But as the only ingredient in a seedling mix, or a WS mix, is it coarser than necessary? I hope Jonna chimes in with her favorite particle sizes!)

By the way - learn from my mistake, though few experienced gardeners would ever make this one.

Don't try to surface-sow tiny seeds on a coarse medium. I tried to sow a 128-cell plug with 13 kinds of petunias, using my own mix with fairly coarse pine bark added.

Of course the tiny seeds fell into the cracks and never saw any light. If any DID germinate, they never emerged from the surface.

If you surface-sow onto coarse medium, sprinkle a layer of finer vermiculite on TOP of that medium, to support tiny seeds!

I'm guessing that nice, big vermiculite like 1/10" and 1/8" nuggets would need a little finer vermiculite on top to support WSing small seeds or very small seeds.

On the other hand ...

http://www.seedsite.eu/article... (3/4 of the way down)

@JonnaSudenius is the expert on WS with vermiculite in sealed containers. Her website doesn't say that you need a layer of fine vermiculite to support small seeds, though she does say:

"Gently press the layer with the bottom of another container to settle the vermiculite. "

"Use a spoon to lightly cover seeds that require it, and if necessary, gently tamp down the surface with the bottom of another container. "

Also:
"- Seeds that need light to germinate are exceptionally good candidates for sowing in vermiculite. Just scatter the seeds on the surface; the continuing expansion of the moistened vermiculite will provide good surface contact.
...
It may seem that some areas are covered deeper than necessary due to the clumping action of moist vermiculite, but don’t worry; vermiculite admits greater amounts of light than soil mixes."

Since vermiculite lets more light penetrate than bark-and-peat mixes, maybe it is less important to keep small right on the top of the surface.

P.S. to Jonna: if you would prefer that I not take direct quotes from your website, let me know and I will delete them or re-word them (paraphrase them).

I use that brand of course vermiculite and planted petunias by sprinkling on the surface and they germinated in less than a week.

That answers that. Thanks, Arlene.

You're welcome!

There is no size of the vermiculite on the bags I use. I use the vermiculite that is usually sold as insulation at stores that sell building materials, so it is not really fine. The size of the vermiculite I use, varies from 3 mm to 6 mm. It doesn't matter if tiny seeds fall a bit deeper, they still will get enough light. The vermiculite doesn't weigh much, so the seeds won't have much troubles to fight their way to the surface.

@RickCorey : you can take direct quotes from my website as much as you want.

JonnaSudenius said:... I use the vermiculite that is usually sold as insulation at stores that sell building materials, so it is not really fine. The size of the vermiculite I use, varies from 3 mm to 6 mm. It doesn't matter if tiny seeds fall a bit deeper, they still will get enough light. The vermiculite doesn't weigh much, so the seeds won't have much troubles to fight their way to the surface.

>> The size of the vermiculite I use, varies from 3 mm to 6 mm.

Ahh! The "coarse" A-3 size is finer than what you use! Thanks for clarifying that.

The stuff I buy is just labeled "fine" or "medium" I think.

Karen

Grading isn't necessarily uniform between companies, but this is what I have:

Left: Grade 2, Fine .. .. .. .. Right: Grade 3, Coarse

Winter sowing. I did some today. Fourteen jugs worth, added to my previous whatever number that was.

Also. Sprouts. I have them. In all the right jugs. Looking perky.

Today was a warm day; tomorrow will be cold and down in the teens tomorrow night.

Perfect!

leftwood -- thanks for those images.

I have the fine stuff... will have to look for #3

Myself, I prefer the fine stuff for most seeding, but I agree with Jonna that it really doesn't matter that much. I think it makes me feel better because there is more surface area of the seed in contact with the actual media, and I don't have to rely so heavily on high humidity to get the seed to imbibe sufficient water.

It's funny about vermiculite that the finer the grade, the less water it holds! Yet, that doesn't mean there is more air space in small grains; the opposite is true.

Thanks to everyone for all the vermiculite info! It is very much appreciated!

I certainly took notes! It is interesting.

I generally keep the fine kind to sprinkle over mix when seed starting, and the coarse kind for amending potting mix. I've used the coarse kind in the past for seed starting in the closed container, and had good results. In my most recent attempt I inadvertently grabbed the fine stuff to germinate echinacea in a closed container. I currently have some echinacea sprouting in there, and a few have a first true leaf and are ready to prick out. Some of the smaller ones look like they're rotting. I don't think many are going to make it, especially if I don't pot them up soon.

Overall, I've had better results with the more coarse grade.

Karen

There is another type sold by a garden center here.
The vermiculite is not in chunks ,but in small flakes which do not hold the moisture.
It is okay for sprinkling on surface of soil mixes, but not great for seed starting.