Perlite vs Vermiculite for Starting Mixes?

[Greatgardens]

I use and very much like Burpee's Coir Organic Seed Starting Mix, but I am mildly concerned that it does not have enough porosity. Incidently, overall I've had much better germination using this Burpee product than with peat starting mixes.

So I plan to make up some test batches with a perlite or vermiculite addition -- say 10% as a starting point. I realize they are slightly different in their effect, but I am leaning toward the vermiculite mostly because of its finer and more uniform particle size.

Any thoughts on one versus the other for this application?

-GG

[clkeiper]

it depends on the particulate size. If you use fine vermiculite it packs pretty well. I don't like it except to lightly cover seeds.

[nyrfan]

The fine vermiculite will only make the possible lack of porosity more of an issue. You can use the larger grade (accordian-type) but I recommend perlite.

[TexasTomat0]

I vote perlite also, I had problems with damping off in the vermiculite. Seems like it kept the soil a little too most.

[Koala Doug]

I'd also vote for perlite only.

[FourOaks]

I have been making my own seed starting mix for years. I was always in the peat and perlite camp. This year, I switched up to Vermiculite. I like it far better!


For the mix, I used coarse vermiculite. To top the seeds, I used fine vermiculite.

[Ricky Shaw]

It depends.

My basic mix is 60% peat or coir with 40% perlite and use this alone if I'm cold treating. The lower temps make evaporation less a factor and this reduces the chances of damping off as well as other pathogens that thrive in cool damp conditions.

For the majority of seedlings that are grown in a more traditional 12hr light/ 72-78 degrees under a fan and 12hr dark/ 65-70 degrees, I top dress with 50/50 peat and vermiculite. My dry climate coupled with the fan and warmer conditions dry out the small seedling pods quickly and also form a crusty mat that is difficult for later germinating seeds to punch through. Which happens often because I plant 4 seeds to a cube and remove the siran wrap as soon as the first seeds sprout, and often it's another day or two till other seeds pop up. Cole Robbie taught me that trick.

[Greatgardens]

I ran a little test putting hort. grade vermiculite in a small jar and then adding water. It did suck up the water and swell significantly. Surprising to me how much it swelled. Of course, no such issue with Perlite.

Anyone know of any good sources for fine perlite? I could screen the bigger stuff out, but that would be my second choice to buying what I want.

-GG

[FourOaks]

Originally Posted by Greatgardens

I ran a little test putting hort. grade vermiculite in a small jar and then adding water. It did suck up the water and swell significantly. Surprising to me how much it swelled. Of course, no such issue with Perlite.

Anyone know of any good sources for fine perlite? I could screen the bigger stuff out, but that would be my second choice to buying what I want.

-GG

Your local hydroponic store.

[Greatgardens]

Had another thought -- maybe DE instead of perlite. That is definitely about the right size, and I think I still have some of the DE (oil absorbent) I bought several seasons ago.

-GG

[Cole_Robbie]

I've only had damping off problems with vermiculite when using organic fertilizers, or in a mix that had some sort of organic component, and especially in cold weather.

[nyrfan]

I bought a brick of coconut coir yesterday &, per the instructions, soaked it in 4.5 quarts of water.

However, that amount of liquid was excessive & I ended-up having to drain the expanded coir & combine it with dry Jiffy Mix + perlite, to make an immediately usable media.

I would recommend using only 3 to 3 1/4 quarts of water.

[FourOaks]

Originally Posted by nyrfan

I bought a brick of coconut coir yesterday &, per the instructions, soaked it in 4.5 quarts of water.

However, that amount of liquid was excessive & I ended-up having to drain the expanded coir & combine it with dry Jiffy Mix + perlite, to make an immediately usable media.

I would recommend using only 3 to 3 1/4 quarts of water.

I know this is kinda late, now, but I hope you thoroughly rinsed the CoCo. Last year, I filled up my grow bags, around 48 of them, then continuously rinsed. It was a pain, but worth the effort.

[nyrfan]

I only used about a quart or so of the expanded coir & put the rest in a bag for later use, starting in about 2 weeks.

Since it's already quite moist I'd rather not rinse it & would prefer to dry it out if I could.

[FourOaks]

Originally Posted by nyrfan

I only used about a quart or so of the expanded coir & put the rest in a bag for later use, starting in about 2 weeks.

Since it's already quite moist I'd rather not rinse it & would prefer to dry it out if I could.

The reason I asked, most of the CoCo products are full of salt. Just something to consider. Aside from that, and the price, it is a fine grow medium. Im reusing mine for another year.