Perlite vs Vermiculite for Starting Mixes?

Greatgardens · March 16, 2018

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 · March 16, 2018

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 · March 16, 2018

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 · March 16, 2018

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 · March 16, 2018

I'd also vote for perlite only.

FourOaks · March 16, 2018

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 · March 17, 2018

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 · March 17, 2018

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 · March 17, 2018

Quote:

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 · March 17, 2018

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 · March 17, 2018

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 · March 17, 2018

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 · March 18, 2018

Quote:

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.

Greatgardens · March 18, 2018

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

nyrfan · March 19, 2018

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.

March 16, 2018	#1
Greatgardens Tomatovillian™ Join Date: Feb 2010 Location: Indiana Posts: 1,124	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 Last edited by Greatgardens; March 16, 2018 at 11:55 AM.

March 16, 2018	#2
clkeiper Tomatovillian™ Join Date: Nov 2011 Location: ohio Posts: 4,350	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. __________________ carolyn k

March 17, 2018	#7
Ricky Shaw Tomatovillian™ Join Date: Aug 2015 Location: Zone 6a Denver North Metro Posts: 1,910	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. Last edited by Ricky Shaw; March 17, 2018 at 07:34 AM.

March 18, 2018	#14
Greatgardens Tomatovillian™ Join Date: Feb 2010 Location: Indiana Posts: 1,124	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 Last edited by Greatgardens; March 18, 2018 at 08:15 PM.

March 16, 2018	#3
nyrfan Tomatovillian™ Join Date: Feb 2017 Location: NJ Posts: 123	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.

March 16, 2018	#4
TexasTomat0 Tomatovillian™ Join Date: Mar 2017 Location: Central Texas - Zone 8A Posts: 196	I vote perlite also, I had problems with damping off in the vermiculite. Seems like it kept the soil a little too most.

March 16, 2018	#5
Koala Doug Tomatovillian™ Join Date: Dec 2017 Location: Detroit Posts: 688	I'd also vote for perlite only.

March 16, 2018	#6
FourOaks Tomatovillian™ Join Date: Mar 2016 Location: NC Posts: 511	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.

March 17, 2018	#11
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	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.

March 19, 2018	#15
nyrfan Tomatovillian™ Join Date: Feb 2017 Location: NJ Posts: 123	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.