Might trial it with the holes next time I do a batch of seed. Seeing as you had good results, I think it's worth a try.

PD - I remember a trial back in the 90s using CO2 from sewage treatment works - the CO2 was pumped into large plastic domes to see if tree growth increased.

The theory is if you can provide all nutrients the only other limiting factors are light and CO2.

The growth was certainly increased - as far as I recall substantially... But the wood was not as good in the forestry or native trees (if I recall). But intial growth was 20 - 30% more in the first year alone!

I would expect the same, if not better results from herbacious plants - and maybe even cactus.

It would be worth a try to increase CO2 for the first year of growth.

How you do it? Well... that I can't answer. I just suggested to Hornet putting a shade house with clear plastic over the top of my sceptic tank. I assume it vents naturally so the CO2 will collect in that.

Other methods are dry ice, CO2 cannistors, marble chips and acid (haha - vinegar would work, but too slow)... Or any other various ways - maybe breathing on them???

If you know of any studies of the sort, i am sure they'd be interesting.

I might just have to try the shade house over the sceptic tank and see what results I get... but not this year!

Interesting stuff slim6y


Another way that is apparently good fro making seedlings grow quickly is to feed them with a quarter of the recommended measure at every watering/misting of the seedlings. That is one from the man himself, Trout.

I think the only drawback with this one is it can eventually makes the plants weak or bloated. I think is particularly the case with Gymnocalycium sp. and related genera. I will read up on this a bit more and see if I can find some more good literature on the subject. Be really good to have a feed different seed techs written up that we can sticky. Any takers?

Slim6y - Mmmmmmmmmmm the odour would be lovely haha.
Have a look at a few hydroponic supply sites, they should have co2 delivery systems available for use in shade houses.


Trig - i will get a few different lots of the same seed going and trial a feeding regime, got plenty of spare spachianus seed that i was planning on using on something like this. Will use miracle grow and one other fert for a comparison, got any suggestions anyone?, am after a reasonably easy to obtain/common fert.

I would think a high Nitroogen feed might be good. Though it is commonly suggested that high Potassium is better.

Depends what results you want to achieve

A high N feed might result in bloating splitting?

Something common like Thrive might be worth a shot PD?

I think it might be. Tell you what I'm heading up to the shops tommorow. I will have a look around at the common plant food/fertilisers and get an idea of the best NPK ratio.

Will let you know what lloks good, then you can check it out.

I have seen a fertiliser at kmart especially for cacti and succulents i think its yates or something, im not sure how common it is or even if they will still have it. Would be good to compare something like that to regular old miracle grow you think?.

Yep just checked, yates "thrive" cactus and succulent liquid fert

yeah I know the stuff, I have only ever seen it once though. wouldn't mind trying it.

What do seedlings with rot look like?

i think they just go soft, you look at them and they have a watery look to them, like they are a bag of water.

What hornet said, they usually also collapse on themselves and often have a orange or brownish colouration.

Had a bit of a look around PD, Thrive had something like 20+ % N, though I saw another one that was for flowering and fruiting that had a much lower N and a decent amount of K. Though it might not be that appropriate?

cheers all for sharing your knowledge

If your gonna use CO2 its only useful at night as cacti are CAM plants they only open their stomata at night. It is also possible to kill plants if they dont get enough O2.