Tebuconazole and Trifloxystrobin: safe for very small cacti seedlings?

[T.bridgesii]

Same here...too spendy. I found some other stuff online...only $1025.00 USD for a gallon

I'll be getting 2 gallons just to be sure I don't run out soon.....said no one ever.

Something way more affordable and locally sourced is for me.

Yeah. I’m in the UK, so ordering from Germany would ordinarily be fine, but £25 postage for a 20 ml bottle is “taking the piss”, as we say colloquially.

I sprayed one of my seedling pots as a test last night with the systemic spray I’ve got, and nothing in that pot is looking the worse for it yet. I guess I will give it a little longer just to be sure, and then treat them all and hope for the best. I’ve used this spray on my (adult) cacti before with no ill effects, but was just concerned about the seedlings being really sensitive and vulnerable.

I’ve got the lid propped open, and am keeping it a lot drier in there, and that still seems to be working (though unfortunately I can’t keep the temperature up as high as I’d like with the lid not closed - not sure what the answer is there yet).

There’s only one seedling that I’m actively worried about currently. The only one still showing signs of being attacked by fungus is the variety I spoke of above where only one seed germinated. Just lucky, I guess. Most are fully recovered, and I only lost a couple.

[greenknight]

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My pots are too deep really (my first mistake), so bottom watering seems like it would mean having to have quite a large volume of water in there before it reaches the roots.

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Not really, since the mix that's below the root zone doesn't dry out - it's not exposed to the air, so no evaporation. The seedlings will soon send roots down into this zone, though - it's amazing what deep roots a small cactus seedling can develop.

[T.bridgesii]

Not really, since the mix that's below the root zone doesn't dry out - it's not exposed to the air, so no evaporation. The seedlings will soon send roots down into this zone, though - it's amazing what deep roots a small cactus seedling can develop.

OK, maybe I’ll give it a try after I keep things on the dry side for a couple weeks or so and treat with fungicide. I thought having that much volume of stagnant water in the media in the pots would be asking for trouble, but maybe it would be OK once the lid is off.

From everything I’ve seen after I planted my seeds, it seems like most people use trays that are a couple inches deep. My pots are mostly square nursery pots that are maybe 100mm deep.

[greenknight]

It doesn't "go stagnant" because there's plenty of air present - it's only damp, not saturated. With saturated soil, water fills all the pore spaces so there's no air. That's when you can get problems - if this condition lasts too long, anaerobic bacteria start to grow, which sours the soil.

While watering from the bottom as I described can't saturate the soil, watering from above can, as explained here: http://gardening.stackexchange.com/ques ... ater-table

Since water doesn't come out of the drain holes until after the soil becomes saturated, it's hard to get the pots watered deeply without saturating them if you water from the top - but if you don't water deeply enough, your seedlings will grow only shallow roots. Bottom watering avoids both problems.

Bottom watering of adult cacti is not recommended because it allows salts to build up - better to flush out the soil a bit with each watering by letting water run out the drain holes. It takes more than a few months for salt buildup to become a problem, though, there's no worry with bottom watering young seedlings.

[T.bridgesii]

It doesn't "go stagnant" because there's plenty of air present - it's only damp, not saturated. With saturated soil, water fills all the pore spaces so there's no air. That's when you can get problems - if this condition lasts too long, anaerobic bacteria start to grow, which sours the soil.

While watering from the bottom as I described can't saturate the soil, watering from above can, as explained here: http://gardening.stackexchange.com/ques ... ater-table

Since water doesn't come out of the drain holes until after the soil becomes saturated, it's hard to get the pots watered deeply without saturating them if you water from the top - but if you don't water deeply enough, your seedlings will grow only shallow roots. Bottom watering avoids both problems.

Bottom watering of adult cacti is not recommended because it allows salts to build up - better to flush out the soil a bit with each watering by letting water run out the drain holes. It takes more than a few months for salt buildup to become a problem, though, there's no worry with bottom watering young seedlings.

Thanks, that all makes total sense, and aligns with what I already know about this stuff. I actually have read a similar article before explaining the concept of perched water tables in pots, and learned a lot from it! Seems a lot of “gardening lore” about drainage is actually total nonsense.

I guess I was feeling reluctant to allow any water to sit in the tray again, because water collecting in the tray from watering seemed to correlate with the start of my fungus problem, but I was originally watering from the top with a spray bottle and letting the water drain through, so the surface was staying pretty moist and I was keeping the lid on so humidity was very high, and that might have actually been the real problem. Was (probably wrongly) under the impression that the seedlings would dry out if I didn’t do that, because what they’re planted in is not particularly absorbent, but maybe the water will wick up just fine from below - I’ll just have to try it and see how it works out in practice).

I don’t think there is much chance of an anaerobic environment in the pots, even if they are frequently watered, because I planted the seeds in a heavily mineral based mix (it’s just my normal adult cacti pumice/akadama/lava rock stuff) with maybe 25% compost mixed in. I ended up sprinkling a little extra compost on the very top to get them started and hold some moisture around them, since otherwise they’d be trying to germinate in ravines between dry “boulders”, and that wasn’t a great idea as I discovered. Should be plenty of air gaps in the “soil” as it is really quite coarse (too coarse for tiny seedlings as it turns out - another thing I’ll do differently next time).

So, anyway, I’ll definitely give the bottom watering plan a try, but being sure to maintain more ventilation than before this time around.

Thanks so much for taking the time to help me and my seedlings! I really appreciate it.

Everyone is doing fine so far, and I haven’t had any more casualties. Fingers crossed!

[T.bridgesii]

I’ve just ordered some capillary matting. May as well do this properly.

[claudekim1]

alot of the orange spots can be stopped if you pull your seedling out of 100% humidity. ive had this happen, airflow is more important than anything ever in growing seedlings. soil can be dogshit, seeds can be crap and infected. but airflow will solve that issue. also id go with the trizole fungicide as its curative too. it doesnt cause any issues from what i can tell just dont use too much.

also sulfur does nothing in terms of causing damage to seedlings and lophs thrive in either 5.0 or 8.0 ph. the high ph crap is total bs. and even more so for seedlings

[T.bridgesii]

alot of the orange spots can be stopped if you pull your seedling out of 100% humidity. ive had this happen, airflow is more important than anything ever in growing seedlings. soil can be dogshit, seeds can be crap and infected. but airflow will solve that issue. also id go with the trizole fungicide as its curative too. it doesnt cause any issues from what i can tell just dont use too much.

also sulfur does nothing in terms of causing damage to seedlings and lophs thrive in either 5.0 or 8.0 ph. the high ph crap is total bs. and even more so for seedlings

Thank you! That’s pretty much what I have figured out. I am not sure how people get away with leaving seedlings in a baggie or sealed container for six months, unless they’re using serious fungicides.

Some of mine were starting to get spots of orange fungus after only two weeks of very high humidity/not much air circulation. They’re doing fine now, though, and I’ve even had water standing in the tray for the last couple days, to bottom water them. Since I now have the lid raised off the top of the tray by a couple of inches, they seem to be getting enough airflow to prevent problems (the little vents in the top were nowhere near enough to make a difference, as I found). I did go ahead and treat them all with the fungicide as well, so I’m sure that’s also helping a lot.