Sterilising seed compost

[Maria J]

It may a totally daft thing to say... but... doesn't all this 'sterile environment' they're brought up in make them more susceptible to it all later on when they're more mature?? Wouldn't some exposure to the 'nasties' (obviously not rot!) help them build up a better 'natural' resistance??
(Please excuse my ignorance! As you can tell, I have no knowledge in Biology / Botany etc... Lol!!)

[iann]

Maria, by all means try nature's own "sow 1,000 seeds to get one adult" approach, but I don't have that many seeds

[Maria J]

Oh I'm not intended on trying it Ian, was just curious really! ;-)

[Roy]

Of course nature can take it's course, it's just a question of how far you want to go to swing the odds in your favour. It can be argued it is wrong to get every plant you can from a batch of seeds as you are assisting weak plants to survive.
For the vast majority of seeds germinating them is quite straight forward. It's always interesting to read about new (allegedly, but not always the case when you browse some of the old books) ideas and it is fun to try them out but in my opinion taking notice of a local grower who can demonstrate, not just talk about, successful propagation is the quickest way to succeed.

[David]

Phil Crewe asked whether there was a thiram equivalent over here. A few years ago I was tipped off about a different fungicide, captan, which is a component of some of our rooting hormones (e.g. Murphy). A search showed that captan has been a subject on this forum before. Whereas thiram is "highly toxic if inhaled", captan is "practically nontoxic".

Until I started to use it, I usually had a poor yield of seedlings per packet of seed, rather as Tina reported for her Pachypodiums. As soon as I started dusting the seeds, the change was quite significant, and I sometimes got swarms of seedlings per pot.

The method is to add a very small amount of the hormone (depending on seed size) to a packet, and shake it enough to get the seed coats covered. Then sow as normal.

A friend who is an expert in this sort of thing pointed out that this is only beneficial for surface problems - there can be deeper trouble inside the seeds. Of course, I still get poor or zero germination some of the time, but there are many other possible reasons for that, aren't there?

David Greenaway
Oxford Branch

[Chris43]

Suzanne, I'm sorry, I missed your question much earlier in this thread. The compost I use is my usual JI No 2 that I use for potting, but I sieve it, to get rid of a lot of the more fibrous stuff and larger pieces. I mix roughly 50% of this and 25% washed grit sand and then 25% actual small grit (2mm). I tamp the top of the mixture down and take off any larger pieces of grit. Large seeds I press into the soil, smaller ones not at all, just let them settle. I've never used vermiculite or perlite, so can't comment on mixes with them - except that I know they work. This is just the way I've done it, and it also works.

And Mike, I also got my Chinosol from Roy Mottram. One jar will last me a good while.

I don't worry about the weaker seedlings being germinated - the first winter usually sorts out any such weaklings. It is a good test of survivability of the strongest.

[MikeT]

I'd also put in a word for Cheshunt. I only sterilise compost if I'm using a sealed container for very slow growers (Blossfeldia, Aztekium, etc) which would be swamped by any moss at all. (Abysmal success rates by 2-3 years with such species doesn't qualify me as much of an expert on them, but at least the miniature green blobs no longer just disappear under moss.) I use a hand water sprayer to soak the surface with Cheshunt solution before sowing. I haven't found any problem with reduced germination; this includes Pachypodiums & Adeniums. A few years ago, after reading about Cheshunt reducing germination, I didn't use it one time. Result:- damping off. I never get damping off with Cheshunt. Other than the really slow growers mentioned above, I don't find moss a problem; it grows, but not enough to compete with the seedlings.

Mike T
Sheffield branch

[Phil_SK]

I asked because although I'm aware that Murphy's hormone rooting powder contains captan I've been unable to find it for sale. The only ones I've seen (that are a powder and not a gel) are an organic one (that boasts that it doesn't contain hormones or fungicides(?!)) and vitax and strike 2. Murphy's is still out there, it would appear, but I've not seen it. The database I've looked at doesn't appear to mention thiram, making me wonder if I'd spelled it wrong or something.
I might not bother persuing this but try spraying with armillatox as was recommended in the BCSJ.

[MikeT]

Nick

Smelly usually means anaerobic bacteria

Mike T
Sheffield branch