A little help/advice

[ragamala]

I always now sterilise by microwave. I might well not do this and have success, not only with germination but continued growth, I don't know, I have sterilised (using the old sterilising steam bucket technique decades ago!) but the question I would ask is - Is there any argument AGAINST heat sterilisation? If not then why not do it anyway?

I have never used baggie method except for species that Karlr names, and agree that for those I wouldn't dream of not sterilising compost, and not using sterilised water for that.

[KarlR]

I always now sterilise by microwave. I might well not do this and have success, not only with germination but continued growth, I don't know, I have sterilised (using the old sterilising steam bucket technique decades ago!) but the question I would ask is - Is there any argument AGAINST heat sterilisation? If not then why not do it anyway?

I have never used baggie method except for species that Karlr names, and agree that for those I wouldn't dream of not sterilising compost, and not using sterilised water for that.

Arguments against? Depends who you ask. For me it's too much work. Between kids, wife, work, the house, and other interests and things i need to do, I don't necessarily have a lot of time left in a day for my plants. Saving time on sterilising the soil might be the difference between actually managing to sow on that specific day, and everything and anything else just eating up that time.

Besides, for me it's usually always the seeds themselves that cause any issues. And I'm certainly not going to spend time cleaning seeds before I sow. Perhaps one in ten pots I sow might have a slight issue with fungi, but it's usually easy enough to deal with. Worst case scenario I have to remove the pot in question earlier than intended, but usually it doesn't ruin anything. I had an exception to that last year when almost all my pots of Austrocactus seeds were heavily attacked by fungi. I still don't know why. Other pots in the same propagator had no issues.

But anyway, with sterilising soil I just think it's a case of "your mileage may vary". If it works for you, great. If not, no worries.

Although I don't really have an informed opinion on the matter, there are some who argue that sterilising the soil can leave it vulnerable to being repopulated by a harmful bacterial flora rather than a beneficial one. Some soils will also contain beneficial mycorrhizal communities that may be destroyed by sterilisation.

[David Neville]

I have raised tens of thousands of cactus and succulent seedlings over the past 40+ years and have never sterilised, microwaved or used boiling water for any of my sowings. I have never used anything more than a fungicide to water my sowings, usually either Chinosol or Fisons Filex when it was available in the past, but mostly with neither. I have always found sciara fly (aka sciarid) to be far more of a problem than damping off or fungal problems. Those who recommend use of John Innes composts to avoid sciara fly seem to forget that the John Innes formula includes the use of peat, and in my experience sciara fly can be just as much of a problem in JI mixes as in purely peat based composts. There are of course various chemical and organic solutions to control sciara fly, but the problem is that the initial attack and infestation is often the most destructive, and by the time the problem is noticed it is sometimes too late for some of the seedlings.

[John E]

At Last. What a pleasure to read that someone who really knows how to grow Cacti and Succulents is prepared to grow plants rather than have a dozen different sorts of compost. Personally I have had enough reading about someone growing their plants in neat Akadama dust or asking questions about plants that they should not be trying to grow for at least another five years until they have reaiised just how difficult to grow some plants really are.

[MatDz]

Back to the topic, I don't think I would bother with bags or boiling the soil when dealing with more than 20 pots at a time, but it's a great help if one would rather forget about them for months.

Bags don't work that great with mesembs though, and are great in decimating Crassulacea seedlings if left on for even a day too long.

Edit: I have removed my rather offtopic and personal comment, especially as the addressee has seen it.

[Aiko]

Bags don't work that great with mesembs though, and are great in decimating Crassulacea seedlings if left on for even a day too long.

Some do say that, even Terry Smale used to say that, but I do have a different experience. Well, not with Crassulaceae, but with mesembs I don't really see a problem with them locked in an air tight container while the seeds germinate during a few weeks up to one and a half month or so.

[esp]

Bags don't work that great with mesembs though, and are great in decimating Crassulacea seedlings if left on for even a day too long.

Some do say that, even Terry Smale used to say that, but I do have a different experience. Well, not with Crassulaceae, but with mesembs I don't really see a problem with them locked in an air tight container while the seeds germinate during a few weeks up to one and a half month or so.

I find that too wet and too hot can cause problems with both mesembs and Crassulaceae, but sealed containers can work OK for a few weeks. It's sometimes hard to get the balance, and I often open up to some extent (say) 2-3 weeks after most germination.

[MatDz]

Aiko, esp, both of you nicely explained what I meant - one cannot simply leave them sealed for months. Thank you for the Crassulacea tips as well, I have a second batch of Tylecodon seeds arriving soon, so every bit helps!

[David Neville]

Hi JE. I hope that you and yours are doing ok at this weird and difficult time.
It's amazing how the inexperienced views of newcomers to the hobby are able to complicate and dominate what used to be simply viewed as basic cultivation aspects of our hobby. Over time I am sure things will relate back to those who have experience in our absorbing hobby, and the dedicated growers will endure!

[Pattock]

I have always found sciara fly (aka sciarid) to be far more of a problem than damping off or fungal problems. Those who recommend use of John Innes composts to avoid sciara fly seem to forget that the John Innes formula includes the use of peat, and in my experience sciara fly can be just as much of a problem in JI mixes as in purely peat based composts. There are of course various chemical and organic solutions to control sciara fly, but the problem is that the initial attack and infestation is often the most destructive, and by the time the problem is noticed it is sometimes too late for some of the seedlings.

Microwaving will kill sciarid fly larvae and eggs in the compost. They should then be totally excluded until the bags are opened. In open areas, yellow sticky traps will give a rapid warning of any build-up of sciarid flies (and some other flying pests and the occasional moth) and help to control them if there are only small infestations.