Den. polysema culture help

[SaraJean]

This is my second most frustrating species that I grow (dockrillia cucumerina takes the cake in the number one spot...). Unlike my little cucumber orchid, for the life of me, I can not figure out why the Den polysema doesn’t do well. I’ve killed 3 and my 4th is steadily declining. I have other Latoiura hybrids and species- the shiraishii, macrophyllum, alexandrae, aberrans, and spectabile, as well as others from similar elevations in the PNG area- which grow beautifully and the blooming size ones bloom with no issue. Every one of the polysemas died in the same way. The new growth starts and then starts to rot once it gets about 2-3 inches tall, see attached first picture. Then my older leaves start dropping. Then the older growths start to yellow, stay firm (I.e not rotting) and it dies. I think I have had one new growth, out all 4 of the plants, make it to maturity.

What am I missing in the culture for these? I keep this in the shade house in the summer, with moderately bright light. I have tried both higher and lower light. It is in power sized orchiata with a bit of sponge rock. I have tried LECA with one and straight bark on two others. It gets watered every day this time of the year. The roots look awesome. The other two that were in bark had great, firm root systems as well. My fertilizer regime has been a bit lacking this year, but other years I have just done frequent low doses, and I add CalMag once or twice a month. I have been treating it with Concentric Ag (the old Inocucor) at the recommended rate after the initial inoculation period which has worked well on other orchids. I use KelpMax once a month. It’s outdoors this time of the year in warm-to-hot temps with humid and rainy summer, and warm-to-intermediate winter temps in the winter with moderately high humidity.

Does anyone have any ideas? Are the new growths so prone to rot that I should be super careful to keep water away from them until they are developed? Or maybe try mounting it? It’s gets lots of fresh rain water this time of the year, but could it just be super sensitive to the tap water I use occasionally in the summer and exclusively in the winter? Is it one of the few Latouria types doesn’t like high humidity? I thought these were mostly from lower elevations, am I wrong and should be keeping it in more intermediate temps?

signed,
one frustrated grower that is pulling her hair out...

[Ray]

It might simply be that the Big Easy temperatures are too extreme for the species.

According to the Baker's culture sheet, in nature they see 54°-58° nights and 74°-79° days, consistently all year. There is even a statement "Growers indicate that plants do poorly if grown in continuously warm conditions."

[Jeff214]

I don't have that exact species, but I've noticed a very similar type of die back that you've described in my Den. atroviolaceum, and Den. little atro. The browning of the leaf in your photo was identical to mine.

It is odd since my older growths keep flowering while the newer growths start, stop before they mature, and begin to rot.

The only issue I've had is from watering during cooler months. I suspect that weakened the plant and perhaps became infected by something. The condition continued for three years before I gave up on them. I never tried any antimicrobials.

Sorry that I'm no help! I've just observed a similar thing with my latouria dens.

[SaraJean]

Originally Posted by Ray

It might simply be that the Big Easy temperatures are too extreme for the species.

According to the Baker's culture sheet, in nature they see 54°-58° nights and 74°-79° days, consistently all year. There is even a statement "Growers indicate that plants do poorly if grown in continuously warm conditions."

Bummer. I was really hopeful that wasn’t the case. I don’t really have much in the way of indoor growing space to put this either. I’m now seeing there is two different populations of these, too. One that grows at 1500-1900m in New Guinea. The other on the surrounding islands at 150-700m. I can usually grow things that come from the latter but orchids from former can be a bit hit and miss. Smh...

Originally Posted by Jeff214

I don't have that exact species, but I've noticed a very similar type of die back that you've described in my Den. atroviolaceum, and Den. little atro. The browning of the leaf in your photo was identical to mine.

I WISH this thing grew like my atroviolaceum! The only time I have had issues with any of my Latourias has been when I let them get too dry for their liking. That’s when I would normally see that sort of browning and eventual leaf tip die back. I did not have this particular polysema over the winter but I suppose if I have been growing it too hot the rest of the year, like Ray mentioned, I’ve probably been weakening it beyond repair