Dendrobium nobile - Brown and yellow Leaves

[kozl1756]

Hello, I am a complete newbie to orchids. I started with some basic phalaenopsis about half a year ago and they are doing great. Then a few months ago I thought to expand and acquired a dendrobium nobile. Things were great and the plant bloomed for about 8 weeks, then the flowers started to wilt and fall off. Nothing unexpected. THEN the leaves started to turn yellow and eventually brown. This happened fairly quickly and is on almost every leaf of the plant. The tips of the leaves are the darkest.
There are two brand new shoots that are growing and the bigger of the two has a small brown spot on one of its leaves as well.

See photos.

A few possibilities that I have considered.
#1 - Just normal seasonal leaf changes - does not seem likely because its MOST OF the leaves as well as a small spot on the new shoot.
#2 - Sunburn - the orchid is under artificial light 12 hours per day due to being located in a north facing room. Its a relatively cool light that has been serving me well to grown plenty of other plants (phalaenopsis, african violets, even some wildflowers) with no issues. The nobile has been under this same light for the past few months with no visible effects on the leaves before now.

Im really curious - what does a nobile with NOT ENOUGH light look like?

#3 - Over fertilizing - I do spray the leaves with the .02-.02-.02 MiracleGro orchid mist, and fertilize the roots with 0.5-1-0.5 blooming houseplant food once every two weeks. Were either of these a mistake on my part?

Temperatures are standard household temperatures, typically from 68 to 72 degrees.

Watering - typically 2-3 times per week. The nobile is potted in a fine bark and drains very very well.

Any help would be greatly appreciated. It hate to loose this guy, hes become a favorite.

[estación seca]

Welcome to the Orchid Board! D. nobile hybrids are wonderful, aren't they?

Older leaves do often fall after blooming, but newer growths should not have this happen. Are the leaves doing this on newer growths that haven't bloomed yet?

The plant should be in active growth by now, with new shoots coming from the base. Is this happening? I can't see the base of the plant. Are leaves on new growths also spotting?

Did the plant come in that pot? The pot looks far too big. Many people grow D. nobile and hybrids in the tiniest pot that can fit the roots. This makes the plants top-heavy, but most people find them to grow better in tiny pots. Watering a large pot 2-3 times per week means the interior is probably staying very wet, and the roots might be rotted.

Spraying the leaves of almost any orchid is useless at best, and harmful much of the time. It is better to increase ambient humidity with a humidifier.

They like plenty of fertilizer when new shoots are forming, but it is important to stop fertilizing sometime before the growths mature in mid to late summer.

I would take the plant out of that pot and examine the roots. It is possible most are rotten, and the plant is unable to take up enough water to support the leaves. I would repot into a tiny pot, perhaps 2" / 5cm across, or maybe a little bigger. The fine bark is OK to use. Check to make sure the bark is almost dry before you water again. There is a thread here on using wooden cooking skewers to check wetness inside a pot:
Using skewers to determine when to water

And here is a great guide on growing these, from the company that very well may have grown your plant:
General Care

[kozl1756]

Thanks for the speedy reply!

Yes, that is the pot the plant came in. I will re-pot as you have suggested.

There are two new shoots growing. One does have a bit of browning at the tip of the leaf. I have attached more photos of the base.

Any other thoughts or tips? Do you think, with proper watering the plant can be saved?

[bil]

This does seem to be unusual. Effectively the tips seem to be dying back.
Stupid question possibly, are you fertilising heavily? Only that can cause tip dieback in some orchids.

I too do not like that pot, but for the opposite reason. I think it is too small.

An explanation. Epiphytic orchids like this don't need or want a pot full of medium. They grow in the crotch of a branch, and die quite easily if the roots are suffocated. Looking at the tips of the roots, they don't look happy.

My recommendation would be, junk the pot and clean off the old medium. Find a wide diameter, very shallow bowl or pot, certainly no deeper than 4 inches. I would prefer 2-3 inches as a max.
You can hold the plant upright with a couple of rocks sitting on the medium till the roots grow and grip the pot.
I personally prefer my Dens on mounts. They get watered every day, and seem very happy.

You will hear people talk of 'overpotting.' This danger is real, but it isn't the diameter of the pot that matters, it is the depth. I notice that orchids mostly grow their roots to fit the container, even if the container edge is half a metre away from the plant. I have asked repeatedly if anyone can tell me what benefit accrues to an orchid from having its roots cramped and screwed into a tiny space, but as yet that question remains unanswered.

[estación seca]

Nobile dendrobiums are different. They come from cool to warm forests that are wet in the summer. They have very small root systems compared to Den. phalaenopsis hybrids. They can be set back and wilt if roots dry out too long while in growth. It can be difficult to water them enough in large bark. This is why people grow them in small pots with fine bark, or on mounts they water daily during the growing season

[bil]

Originally Posted by estación seca

Nobile dendrobiums are different. They come from cool to warm forests that are wet in the summer. They have very small root systems compared to Den. phalaenopsis hybrids. They can be set back and wilt if roots dry out too long while in growth. It can be difficult to water them enough in large bark. This is why people grow them in small pots with fine bark, or on mounts they water daily during the growing season

Very small root systems? Are you sure? I have just repotted one of mine into pure moss in a very open, shallow basket. It had to be a big basket, because the root system, when spread out was a disc about 9 inches in diameter, no smaller than the biggest Den phal I have.
I agree that they like plenty of moisture. So far my hypothesis is that given unchecked air and water they grow big and tall, but when on a mount with daily watering, the fact that there is not limitless water stunts their growth.
Same goes for the den phals. Being on a mount seems to stunt them too.

"It can be difficult to water them enough in large bark."
Hell yeah, but then I would never recommend putting a fine root epiphytic orchid into coarse bark. As you say, it would dry out too fast. I think that even fine bark needs a hand, which I do by putting 3 balls of moss around the edge of the pot and filling the rest with fine bark.

[rbarata]

My oppinion: your medium is too dense.
You should se larger bark and increase the size and amount of the inorganics. Your goal is to increase the size of the air pockets inside the medium to aereate the roots and increase drainage.

[bil]

OK, here is a pic of the Den nobile leaves that are falling off my plant.
As you can see, they have gradually changed colour all over till they end up like this. Leaves that look like yours make me concerned.

The orchid is a D nobile firebird, and the steel structure is a holder for the moss I will be growing it in this year as an experiment. This last year it has been growing in a shallow, fine bark with some moss mixed in. It still needed fairly frequent watering, so I am trying the moss, as the bark mix seemed too wet.

[bil]

Now the plant was in a reasonably wide pot (8"), and when the root mass was released it stretched out to 9" as the roots were starting to circle the pot.

The moss holder on the mount was only just big enough.

So, all in all, I really have to disagree with the suggestion that nobiles have small root systems.

If you look at the last pic, which is a nobile on a branch mount, the roots you see there come from the top and right of the pic, and extend down into the Spanish moss. I can't measure them accurately, but those roots vary from 12 to 18 inches long, and as yet show no sign of stopping growth.

[kozl1756]

Alright, well this just made things a bit more confusing with the varying replies.

From a personal perspective, I prefer not to have to water every day. With the job I have, I am often on call and watering daily is sometimes not a possibility. I will definitely not be mounting the plant.

As for the pot, and the medium. Correct me if I am wrong here, but the plant grew up in this pot with this medium, and has been doing just fine in my possession for the past few months, so something has changed...

My thoughts for now are, I will remove the medium and check the health of the root system (how long does it take for the roots to get damaged?). If its unhealthy then I will consider re-potting. I will stop the spray on fertilizer. And monitor the watering much more carefully.

Another question, is this possibly due to the lack of light? Or over fertilization?