Selective overnight wilt on (dendrobium?) bulbs
 

Greetings, dear orchid lovers,

I write in complete despair - one of my beautiful plants (I am guessing it is a type of dendrobium, as I've never seen it bloom and the person who shared the plant with me doesn't know what it is )) went from gorgeous to monstered overnight.

As you can see in the photos, it wilted selectively, with a yellow tint, on a portion of a two-year-old cane, a budding new growth, a section of the oldest cane (from which all these growths began) as well as some roots (again, selectively, and only green tips of the roots).

I've had it for about a year and a half. Growth A is from last year, has just sent out some beautiful roots which seem to be unaffected at the moment. Growth B is from this year, it is just getting ready to send out new roots.

Conditions: grown indoors in medium to coarse bark, repotted about a week ago. Receives full morning sun, shaded afternoon sun. Watered when almost dry - although, I believe, I was constantly overwatering it for the first six months I had it.

About a month and a half ago I used KelpMax at three waterings, after that I have been using a dilute application of 30-5-10 fertilizer (@100ppm N, without pre-wetting the roots) at all following waterings.

Over the last month the plant also has received two applications of beneficial microorganism mix (Bacillus subtillis + others) and an application of Trichoderma natural fungucide last week - all at recommended prevention dosages.

I would greatly appreciate any comments on:

- what this might be - fungal, too much fertilizer, long-term overwatering, etc?
- as well as how to proceed - do I cut off deseased sections, treat with fungicide, do nothing, etc?

Thank you in advance to all participating in the discussion!

Possibly mildew is harming the roots and plant. If temperature is all ok ..... not too cold, then consider having gentle air movement in the growing area. The air can gently move around roots, media, stem and leaves, that can keep fungus, mold, mildew etc at bay.

The existing dark patches on roots. Just temporarily dry the roots, then maybe spray some mancozeb on the roots and stem etc. Repot into fresh lightly damp media.

Dear SouthPark, thank you for your response. I have all patio doors open during the day and windows slightly open at night, so there is plenty of air movement. I am just baffled as to what it actually is to move so rapidly - just yesterday there was not a sign of any problem (((

m.d. -------- hard to say what happened. But ..... clearly the new growth is very much alive and healthy.

So repot the orchid into fresh new media. I recommend an airy media ...... coarse bark, which is what you have been using.

You repotted a week ago into new coarse bark, right?

Was that new bark very dry? Very dry new bark actually takes a bit to become wet. So new bark needs to be pre-soaked a bit - maybe in warm water ------ in order to get it working properly. Otherwise dry bark repels water ..... and maybe your orchid just became dehydrated.

That newest plant looks just fine. And the old leaves don't look too bad as well.

Just repot into new media.

You mentioned that - in the last month, you've been applying various substances. Maybe it is too much - but hard to say right now, as there's not enough information ------ as in --- at the moment, there's uncertainty about the concentration of substances that were applied.

You mention constant over-watering. But the term 'over-watering' will depend on how much water is the media (and how much) ...... how watery, and for how long it remains watery or how long it remains dry. And how wet/dry the media is ---- at various depths of the pot. And how big the pot is, and what sort of pot it is (eg. how big and how many are the drainage holes).

At the moment, it looks like you dried the roots already (from the appearance of the roots in the photos). Is the orchid repotted now?

In that attached photo in the previous post - the blue circled region shows what appears to be a nice healthy plant. Need to look after that one. The other leaves actually look ok too .... from the old growth.

New orchid roots are growing from other old sections of roots too. So it appears that your orchid is still alive and well. You may be over-reacting ..... possibly.

But ------ if I were growing that particular orchid, I wouldn't bother putting all that extra substances into there. I would just provide weak fertiliser and weak mag-cal every now and again ------ and that would be about it.

In your case, since you have kelp max ...... I would just apply that every now and again. And if kelp max (which I haven't used, as we don't have it here in Australia) doesn't have mag-cal in it, then I would apply some weak mag-cal every now and again. My own fertilising schedule is less than most people I think. I just do once-a-month.

While my fertiliser application and mag-cal application is once-a-month ........ I'm pretty sure that the fertiliser etc stays somewhere in the media for a while ----- so that whenever I just water my media with water, there is still fertiliser/nutrients/elements that the roots can get. So it's not as if the orchid merely gets some fertiliser into it for just 1 day in a month.

Dear SouthPark,

Thank you so much for your time in this communication!

Because I have overwatered a few orchids in the past I might have been overly cautious and have, indeed, kept the plant too dry (and became very prone to panic when sudden things happen overnight )))))))...

I have taken note of all your suggestions and will tone down my watering-feeding routine, as well as have a closer look at the media.

Thank you again for your help!

m.d. .... you're most welcome.

Also, not that long ago, I purposely made a watering video ----- not for recommendations about watering -- but just showing what I do when I water my orchids. I find that if a pot is wide enough ..... this particular method works really well for various sorts of orchids.

Click Here (watering video link)

What are your temperatures? What kind of light is it getting? Did the stems receive direct sun as spring progresses? Could insects or snails be eating the roots?

Dear estación seca,

Temperatures are in the 24-27 range at the moment. It only receives full sun in the morning, until about 10:30 a.m., in the afternoon the plant is shaded. The plant is indoors, with many others, no sign of any creepy-crawlies.

---------- Post added at 09:25 AM ---------- Previous post was at 09:06 AM ----------

Oh, thank you for the video - I love to see "behind the scenes" from experienced growers! ))))

This particular guy is in a fairly low but wide plastic pot - which seems a perfect fit for your watering technique!! ))))

What I struggle with is the following: I grow without extra lights - just natural light from an east oriented lounge with glass doors on three sides, so very much dependent on sunlight. If I water heavily but the sun does not come out for the next day (or two, or three!) I feel like the plants are just soaking in the wet substrate (although, I only use medium to coarse bark)... I then switch on the fan to create additional gentle air movement to get the pots to start drying.... but I feel like I am miles away from striking the perfect balance between media water-retention/drying parameters ))