Sterilising seed surface

[cohan]

I remember there was some discussion of sterilising the seed itself in some cases of fungus prone species... I have a friend trying to sow some cacti which need to be started in humid conditions, and she has sterilised medium, (sealed) vessels, etc, and still ended up with some algae.. any thoughts on whether she ought to try sterilising the seed surface and how? Some of the seeds, not all, are very fine and dust like, and if anything might need to be sprayed in situ...

[Lesley Cox]

I can't say I know anything at all about growing cacti from seed but from my alpine/bulb experience, I'd be inclined to sow over clean grit having already mixed in some of the proprietory Trichoderma products in with the sowing mixture. The grit should discourage algae and the Trichoderma should discourage any fungus diseases or moulds. She could use a water-on form, onto the surface of the growing medium but beneath the grit. Just a thought. 

[cohan]

I can't say I know anything at all about growing cacti from seed but from my alpine/bulb experience, I'd be inclined to sow over clean grit having already mixed in some of the proprietory Trichoderma products in with the sowing mixture. The grit should discourage algae and the Trichoderma should discourage any fungus diseases or moulds. She could use a water-on form, onto the surface of the growing medium but beneath the grit. Just a thought. 

I'm pretty sure she'd already be using grit, but I will pass that thought along, just in case... trichoderma, I guess is a fungicide? will pass that along also, tks!
I think the problem (at least in part) is that these are super slow growing species (not all cacti are, these could be matchead size after a couple years, if I'm remembering roughly right) and need to be kept covered for a long time otherwise very hard to keep evenly moist..

[Lesley Cox]

Trichoderma is not a fungicede, but in fact, is a fungus. The products available are made from a number of species I think and she would probably need to Google to find out what names it's available under in Canade, or maybe other Canadians can help with that.

I know about SMALL. I have seedlings a good two years old of Rhodothamnus chamaecistus about 1/8 of an inch high and half that wide. Other things too, though invariably cool/moist loving species. My shortias are growing like runaway trains in comparison!

[Ezeiza]

The standard method is pouring boiling water on the mix in the pot ready to receive the seeds. Let it cool down and sow.

About cacti, the pot is covered with a piece of film to obtain uniform germination. After this takes place, the cover is removed at once to let them grow dry. If they have to remain covered for long, either the seed is old or they are watered at the wrong season.

[cohan]

The standard method is pouring boiling water on the mix in the pot ready to receive the seeds. Let it cool down and sow.

About cacti, the pot is covered with a piece of film to obtain uniform germination. After this takes place, the cover is removed at once to let them grow dry. If they have to remain covered for long, either the seed is old or they are watered at the wrong season.

Thanks, Alberto, the question is not about sterilising medium and pots, etc--she is already doing that, but rather about sterilising the seed, as I have heard of people doing with some sorts of seeds..
Of course there are many ways of raising seed, but many cactus growers keep the seedlings covered for a long time--even a couple of years or more in some cases-- after germination--many species need to be kept moist, and its much easier to keep them moist if covered.
Although I was not sowing any of the extra slow species my friend is talking about, I sowed a number of species last year--the first to germinate, an Escobaria vivipara form, I uncovered within a relatively short time after germination ( I forget, some weeks) but all of the others I kept covered, and months later, the covered ones were all much healthier-- I tried to keep the uncovered one watered regularly, but obviously it was not the same.... I only uncovered the rest a week or so back when I moved them outdoors (these are all hardy cacti)..

[Darren]

Hi Cohan,

Years ago when I did this with orchid seed I wrapped the (obviously very fine) seed in filter paper (coffee filters are fine) and dipped the whole packet into a solution of the sterilant tablets sold for sterilising baby's bottles etc, for ten minutes, then into a rinse of boiled & cooled tapwater for the same sort of time. It worked OK and involves nothing you can't simply buy in a supermarket.

I struggle with algae in my cactus seed pots too 

[Maren]

Hi Cohan,

I use the same method suggested by Darren, but I use ordinary household bleach, diluted 10 parts water to 1 part bleach.

I would also suggest that you split the seed into batches, using different methods for each batch, just in case.

[Maggi Young]

I can't say I know anything at all about growing cacti from seed but from my alpine/bulb experience, I'd be inclined to sow over clean grit having already mixed in some of the proprietory Trichoderma products in with the sowing mixture. The grit should discourage algae and the Trichoderma should discourage any fungus diseases or moulds. She could use a water-on form, onto the surface of the growing medium but beneath the grit. Just a thought. 

I'm pretty sure she'd already be using grit, but I will pass that thought along, just in case... trichoderma, I guess is a fungicide? will pass that along also, tks!
I think the problem (at least in part) is that these are super slow growing species (not all cacti are, these could be matchead size after a couple years, if I'm remembering roughly right) and need to be kept covered for a long time otherwise very hard to keep evenly moist..

Cohan, for more info on Trichoderma, see this thread
 http://www.srgc.org.uk/smf/index.php?topic=6697.0

[Ezeiza]

Ooooops, Cohan. I would not hesitate to try anything recommended by Darren. Hydrogen peroxide, used for "resurrecting" old seed would also do it, if we are not talking about the same thing.

[Darren]

Thanks for the vote of confidence Alberto!

Milton tablets form a solution of sodium hypochlorite, which unlike some household bleaches (which often contain Sodium hydroxide - caustic soda) is non-corrosive and safer to handle.

If you must use a household bleach it is best to use a thin one rather than a thickened one. These are much easier to rinse from your skin or eyes in the event of an accident. If you go down this route please take safety precautions - gloves and goggles and try not to breathe in the fumes either. I worked as an industrial chemist for the first few years of my career and have seen (and experienced) the damage it can do. It amazes me that relatively benign substances are banned on safety grounds when bleach and hydrogen peroxide are still freely available. By the way - hydrogen peroxide is an effective sterilant and is easier to rinse off but take it from me - the burns it causes are VERY painful...

Sorry to nag but I'd hate to think of a forum friend being injured!

[Ezeiza]

It should not cause any burning or the seed will be destroyed. The lower concentrations used for disinfecting wounds is OK.

[cohan]

Thanks all for continued input! I will show this whole thread to my friend
As a long time (not current) hairdresser, I am familiar with possible effects of bleaches and peroxides