# Another Growing Medium For Seeds Failure .. (Rockwool)



## Cesar Chavez (Aug 8, 2009)

So I decided to germ this time around using rockwool. I picked of a pack of 'Starter Mini-Blocks', 1.5" blocks, and pH'd a bowl of water to 5.5. Next, I placed 3 Mini-Blocks in the bowl of pH'd water, and soaked them for 12 hours(I was told to do this in order to release the glue on rockwool.?). After soaking the rockwool, I placed one seed in each rockwool; think most tip/root down. To do this, I first squeezed the rockwool between my two fingers, to make it moist, and not soggy, and then turned it upside down and made a hole 1/4-1/2 inch deep. I then covered the hole with some of the surrounding rockwool. The seed had been scarified and soaked in distilled water for about 15 hours. Next I took the 3 Mini-Blocks and placed them in a propagation tray, covered with humidity dome, left open 4 breathing holes, and put away in a dark place. I placed a temperature probe inside dome to monitor temps. Stayed between 71-76, humidity 70%+, for the last 6 days, 5 if you only count from planting, and not pre-soak. Either way, still have no seedlings popping. The seeds genetics are solid. What could I possibly being doing wrong this time? Any and all information is appreciated.., thanks.


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## StoneyBud (Aug 8, 2009)

Cesar Chavez said:
			
		

> So I decided to germ this time around using rockwool. I picked of a pack of 'Starter Mini-Blocks', 1.5" blocks, and pH'd a bowl of water to 5.5. Next, I placed 3 Mini-Blocks in the bowl of pH'd water, and soaked them for 12 hours(I was told to do this in order to release the glue on rockwool.?). After soaking the rockwool, I placed one seed in each rockwool; think most tip/root down. To do this, I first squeezed the rockwool between my two fingers, to make it moist, and not soggy, and then turned it upside down and made a hole 1/4-1/2 inch deep. I then covered the hole with some of the surrounding rockwool. The seed had been scarified and soaked in distilled water for about 15 hours. Next I took the 3 Mini-Blocks and placed them in a propagation tray, covered with humidity dome, left open 4 breathing holes, and put away in a dark place. I placed a temperature probe inside dome to monitor temps. Stayed between 71-76, humidity 70%+, for the last 6 days, 5 if you only count from planting, and not pre-soak. Either way, still have no seedlings popping. The seeds genetics are solid. What could I possibly being doing wrong this time? Any and all information is appreciated.., thanks.


All I can do is tell you how I do it and you'll see the differences:

First, the rockwool: (From a popular Gardening Website: "It is a common belief that Grodan (Rockwool) is alkaline and that one has to continuously adjust the pH. This is not true. When Grodan is new it contains some residual lime from production. Everybody should soaks the rockwool in no lower than pH 5 water the day before use. This is done to dissolve the lime. The lime will make the pH value raise a full point. Immediately before use; you flush the rockwool with your nutrient solution. When you flush, you also flush out the dissolved lime. From this point onwards rockwool does not change the pH in anyway.
Exception: If you condition your rockwool with a pH lower that 5, you may also damage the fiber itself. As an example: If you use pH 4 water for conditioning, the pH the day after will be 7. The lower pH you use the higher it jumps. Once the fibers are damaged it might take quite a while before the pH stabilizes. So never go below pH 5 with rockwool."

After the soak and rinse of the cubes, I open the little hole in each one so that it's about 1/4 inch deep and just large enough to fit a seed into.

I drop one seed per cube in, and that's it. No covering, no further than 1/4 inch down no pressing, no nothing.

Then I put it into my germination tray with a heat mat under it. The heat mats aren't adjustable and have only one temperature.

I put four little foil spacers under the corners of the tray dome to hold it at about 1/4 inch open.

I put the tray in the dark and wait 3 days.

After 3 days, any viable seeds have germinated and I can see tiny little roots down in the holes. I wait another day or two until a seedling starts making it's way up from the hole and I put a 150 watt HPS over the tray at 12 inches.

Within a few days, all of the seedlings have pushed their way into the air above the rockwool cube and I wait until each has shed it's seed casing before moving the light to 8 inches.

As soon as each seedling has become sturdy looking, I move the seedlings under a larger florescent light at 6 inches and slowly move it closer as the seedlings grow.

As soon as the seedlings are all healthy looking and the leaves have unfolded good with new growth showing, I put them into dirt so that the stem is buried almost all the way to the first leaf set.

All of my crops are grown from clones. I raise the seeds until sexed, get rid of the males and grow the females until I can take clones from them and root them.

The heating mats raise the temperature inside the dome to about 80-85F.

Seeds love it. I've had more success using the germination center with a heat mat than any other method I've ever used.

One of the keys is to NOT bury the seed deep, but to leave it about 1/4" below the top and leave the top of the hole OPEN.

As soon as I started doing this each time, my germination success increase dramatically.

This also works with almost any seed. I've used that germination center for about 100 different types of plants with the same success.

Frankly, I love the thing.


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## Cesar Chavez (Aug 8, 2009)

Thanks StoneyBud! Great information. Question tho.., if i have a commercial heating mat, one with a temperature controller and a 30" capilary tube with sensing bulb, what setting should I set it on? Believe it does 40-100 degrees. Tried using it in the begining, but didn't put in the sensing bulb, so I had sun-like surface heat going on ;-p Fried 29 out of 31 .. Do I put an extra rockwool in propagation tray so that the sensing bulb can be placed in? No need to squeeze out any water after flushing? How about filling propagation tray with water? Sorry for the questions, done the research, read countless articles, just can't seem to get the green thumb. Thanks again!


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## StoneyBud (Aug 8, 2009)

Some strains of MJ will germinate as low as 65F, but not many.

For all but a few strains, 75-85F will cause germination.

Never go above 90F during germination.

78F seems to be the best over-all temperature for MJ germination.

If you set your mat to stay between 78 and 85, you should have great success.

Also, never wet the seeds or let it dry out. Just keep the rockwool moist.

After soaking the rockwool, just rinse it good with a 1/8th strength nutrient mix.

I would suggest spending the $10 for the set-heat mat. Why mess with anything else? You've had enough failures.

No, do not squeeze the cubes, ever. It damages the fibers and can make your ph go nuts.

No, do not fill the propagation tray with water. Keep the rockwook MOIST, not wet, not dry, ever.


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## StoneyBud (Aug 8, 2009)

I didn't mean to make it sound like all seeds would germinate in a few days.

I also grow "Super-Hot" peppers. Some of them take as long as 45-60 days to germinate.

I've also had some MJ seeds germinate where I could see the seed cracked in as little as 12 hours.

Mother Nature loves to keep us wondering how she does it!


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## Cesar Chavez (Aug 8, 2009)

True. .. I am planting Skunk #1's from Sensi Seeds. I had 10. 7 in rapid rooters, only 2 popped above the surface. One is gorgeous, the other, slow and small, considering killing it. Took the remaning rapid rooters and cut them open to see what was going on. One sprout looked like it just sprouted inside and died. A few didnt germinate, so I took them and threw them back in distilled water to see if I could revive them. One did, but yet to see it pop either. Then the other 3 were as mentioned above. So yea.., not going so well. But I am eager to try your method next.


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## Cesar Chavez (Aug 9, 2009)

So wanted to update anyone who has been following my thread. On your advice StoneyBud, I pulled out my commercial heat mat and began tinkering with the temperature controller. First picture is of heat mat and my germination setup. Second picture is of the temperature controller, notice it is set somewhere around 74-75. The last picture shows the Mini-Cube which contains the sensing bulb, a Mini-Cube with meat/barbecue thermometer stuck seed deep, and a window temperature instrument. I also have a honeywell wired sensing probe that is hooked up to a base controller, it is placed at seed level. Now onto my questions. I seem to be getting a few different temps. The Honeywell sensing probe ranges from 80.6-87.8, and when the sensing probe reaches its peak, 87.8, the window gauge registers 92-94. However, the meat thermometer placed in the rockwool stays between 77-80 the entire time. My air temperature outside of the dome is around 76. Which temperature reading should I be focusing on more? The probe and window instrument gauge? Or is the meat thermometer more accurate for seed germination? Thanks to anyone who may reply.


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## Cesar Chavez (Aug 9, 2009)

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## ArtVandolay (Aug 9, 2009)

The only thing I do differently is sprout the seeds in a wet paper towel in a zip lock bag.  When they grow a little tail I put them tail down in the rockwool, etc.


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## StoneyBud (Aug 9, 2009)

Cesar Chavez said:
			
		

> So wanted to update anyone who has been following my thread. On your advice StoneyBud, I pulled out my commercial heat mat and began tinkering with the temperature controller. First picture is of heat mat and my germination setup. Second picture is of the temperature controller, notice it is set somewhere around 74-75. The last picture shows the Mini-Cube which contains the sensing bulb, a Mini-Cube with meat/barbecue thermometer stuck seed deep, and a window temperature instrument. I also have a honeywell wired sensing probe that is hooked up to a base controller, it is placed at seed level. Now onto my questions. I seem to be getting a few different temps. The Honeywell sensing probe ranges from 80.6-87.8, and when the sensing probe reaches its peak, 87.8, the window gauge registers 92-94. However, the meat thermometer placed in the rockwool stays between 77-80 the entire time. My air temperature outside of the dome is around 76. Which temperature reading should I be focusing on more? The probe and window instrument gauge? Or is the meat thermometer more accurate for seed germination? Thanks to anyone who may reply.


The temperature where the seed is, is what counts. I have no idea what results you'll get with what you're using. Seems like an awful lot of stuff to use when a $15 heat mat that's made to do the job is available. Maybe that's just me. What I use works for me.

Good luck.


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