Cypripedium browning leaves

naoki · Jun 1, 2015

What could be the cause of browning leaf tips for Cypripedium?

This C. guttatum is in the 3rd summer after deflasking (from Spangle Creek Lab, seeds derived originally from Anchorage, AK region). Out of 8 or so seedlings, only 2 are surviving.

The leaves seem to become brown too early. Sometime, browning stops partially, and the green part remains green until fall. They do seem to come back (and grow somewhat bigger every year). I tried almost no fertilization, fairly shady spot, and reduced watering last year (and they had the same issue). This year, I'm trying more fertilization (30ppmN MSU+MaxiCrop+HumicAcid with occasional Aspirin water) for the early season. Also, I was exposing it to more direct sun light this year (from the experience visiting the natural habitat of this species). Then I noticed the brown leaves a couple days ago, and moved them to a shadier place. Around that time, it was a bit hot (for fairbanks) at 80/50F max/min temp.

The right individual is the one affected more (the photo above). But the larger one on the left (with 3 growths) is also starting to show the brown tip.

Any ideas? Other bigger (near flowering) Cyps (C. parviflorum, C. reginae, C. californicum) don't have this issue.

PaphMadMan · Jun 1, 2015

Doesn't Cyp. guttatum come from some very low fertility environments? I would suspect tip burn from high salts (for the species), despite your attempt at a low fertilizer rate. Or maybe a pH problem.

gonewild · Jun 1, 2015

Calcium deficiency?

KyushuCalanthe · Jun 2, 2015

It may sound silly, but it could be heat stress depending on the microclimate you've got them in. I used to have lots of problems with browning due to heat stress when I grew my Cyps near the house or any concrete due to radiational heating. Once I moved them under some azaleas amongst ferns they did much better. Of course southern Japan is a tad warmer than central Alaska!

Other than that, there must be some issue with the roots. Perhaps they are too warm in the pot or…

This species is super sensitive to heat - anything above 80F is detrimental as far as I know.

naoki · Jun 2, 2015

Thank you all for ideas.

Kirk, I went with no fertilizer (probably less than 5 times with weak fertilizer within the season) last year. But I still saw the issues (although it occurred a bit later than this year). So it is a possible cause. But the number of shoots didn't increase this year after the no fertilization year. So I increased the fertilization rate for this year. I could have done too much, though.

Lance, I haven't thought about it. Indeed, according to my friend who is a geology professor, the region where we found C. guttatum has limestone based soil. But I haven't heard anyone mentioning higher requirement of Ca for this species. David (Monocotman) grows C. calcecola in normal Perlite based mix. But maybe I'll try increasing a bit with Ca.

Hmm, I think heat could be the cause as Tom pointed out. I thought that the climate shouldn't be a problem because they grow naturally in my region. But I haven't thought about the microclimate/pot-environment. It could have happened early this year because we had unusually warm spring, and maybe I was too late to move it to shadier spots. When they are growing in the ground, they may be able to handle direct sun and higher air temp (because soil temp is more stable). But as you said, the pot temp can increase rapidly. So I probably need to keep it in much shadier area than in the nature.