Are you fertilizing regularly?

Al

I'm using DynaGro FP & Protekt in the watering water, at 1/4 strength. So it's being fertilised weakly when it's watered, which is only when it's fairly dry (as judged by look & feel of mix, weight of pot & wooden skewer). It is not that often as it's not growing much and it's winter here anyway.

Are you thinking too much? Too little? I fertilised immediately after repotting, before reading that I should have waited for the new growth...

One question I've been meaning to ask, for this plant and generally, is does using protekt skew the fertilising rations ie. NPK FP 936 + protekt 003 = 939?

Back to the calathea: I'd love to hear any opinions or advice about my problem! I'm concerned I'll kill it for good if I repot it twice, but is it headed for death from spreading rot if I don't?

Thank you for your reply, that is reassuring regarding the fertilising ratios. I don't 100% follow the reasoning but happy to take your word for it. And using mls & liters is very considerate of you! Yes it's winter here and I don't want to be repotting unless it's do-or-die (in fact I had hoped to not touch this plant again for a couple of years), so if you don't think there's any rush to get the dead section out I'll leave it. Would there be any point to treating it in the pot with something antifungal?

Most of my plants are in plastic pots and I find lifting them to see how light they've become definitely helps gauge when to water, but the couple I have in ceramic planters I can't tell by doing this, so once the surface looks dry I try the skewers. Then when I do water I take them to the sink or shower, water a little at first then go back a few minutes later and water until a fair bit is coming out the bottom then let drain 10-20 minutes or longer. Occasionally I flush the pots through with plain water.

This particular plant I'm quite keen to keep alive, because I like it and because it's been such a pain that I've invested a lot of time and mental energy into it! It's my challenge :)

I think an anti-fungal application is a good idea. I don't know if you have Bayer products there, but many of their products for disease control contain a systemic fungicide called Tebuconazole. Another systemic I use is Cleary 336, but it's very pricey.

Your extra efforts when it comes to watering habits are admirable, and should pay off. If you think your soils are still too water-retentive, I suggest you read this thread about ways to deal with excess water retention. It outlines some ways you can put simple science to work and eliminate a notable volume of water that would otherwise hang around and cause trouble.

It really sounds like you've been doing some good research and pretty much have a productive path laid out, for which plaudits are appropriate. Strong work!

Al

Thank you Al, I appreciate the compliment! All my research has been done right here of course, so the compliment can bounce right back to you :)

The Bayer fungicides here are for commercial crops, not available to the general public. We have products such as Yates Fungus Fighter (myclobutanil), but it's labelled for garden plants. One that has directions for house plant use is Kiwicare Root Protect Aliette containing fosetyl-aluminium, which doesn't sound like your usual class of anti-fungal. And then there's copper, sulphur, potassium permanganate - not sure any of those would be wise on house plants. Plus more organic methods such as Bacillus subtilis. Does anyone use hydrogen peroxide as a soil drench rather than a surface spray?

When that last leaf of the clump completely yellowed I removed it, and the stumps left behind seem drier now, which is better than rotten. I think I'll just keep an eye on it for now. Can bring in the big guns later...

Thanks again!