Perlite vs Vermiculite for Starting Mixes?
 

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

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.

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.

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

[B][SIZE=3][FONT=Garamond]I'd also vote for perlite only.[/FONT][/SIZE][/B]

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.

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.

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

[QUOTE=Greatgardens;689743]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[/QUOTE]

Your local hydroponic store.

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

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.

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.

[QUOTE=nyrfan;689887]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.[/QUOTE]


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.

I bought a bag of DE oil absorbent today ($6.59/15 lb bag) at Autozone. Perfect sizing, I think. So I'm going to make three small batches of Burpee (bagged) coir seed starting mix + vermiculite or DE or perlite. We'll see how they do for seed starting. What started this whole quest was trying a peat pre-mix that stayed too wet and ended up nearly killing several varieties. Of course plenty of the blame was mine, not recognizing the "wet distress" that was happening until some pretty serious damage was done. But as a result, back to coir -- plus some additional drainage material.
-GG

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.