Dendrobium leaves are turning yellow and fall off

[K-Sci]

Originally Posted by rbarata

Seems to be a Den Phal. Never had any of these but I think they are deciduous too.
Let's see what others say.

Rbarata, you're mostly right. These plants might be called semi-deciduous. A few, some, or of all the leaves on a Dendrobium phalaenopsis hybrid can drop in the fall. This varies by hybrid and growing conditions. Also, the lower leaves will drop on new canes even as they are still growing. A picture is worth a 1000 words,so I went out to the greenhouse and took a photo of one of my Dendrobium phalaenopsis hybrids.

The plant in the photo is about to flower from last year's growth (just learned that they can do this), and just beginning to spike on the newer growth. It is a very happy plant.

The 1 year old flowering growth has no lower leaves because the lower leaves dropped last fall. Two years ago, I gave my Dendrobiums a rest beginning in the fall (reduced watering) and all four of my Dend. Phal. hybrids dropped all their leaves. In the photo, the lower leaf of the newest and largest growth is just starting to turn yellow. I always expect at least some lower leaves to be lost beginning about this time of year. All the canes older than 2 years have no leaves at all.

If only the leaves of the older growths are turning yellow, and the lower part of the stem shows no signs of rot, the OP has no reason to be concerned. This could have occurred due to reduced hydration from partial root loss result when repotting at the wrong time of year, combined with a drop in humidity in the new environment. The right time is in the spring when a flush of new roots start from the newest growth.

-Keith

[estación seca]

The many Den phal hybrids I've seen grown in different greenhouses kept above 70 F / 21C in winter and watered well all year retained all their leaves for 5 years or more. They also flower from old canes along with young canes. They can be kept alive and flower at cooler temperatures with less water, but they make a real show with better care.

Very few people keep their growing areas this warm in winter, which is why people think they normally drop leaves.

[K-Sci]

Originally Posted by estación seca

The many Den phal hybrids I've seen grown in different greenhouses kept above 70 F / 21C in winter and watered well all year retained all their leaves for 5 years or more. They also flower from old canes along with young canes. They can be kept alive and flower at cooler temperatures with less water, but they make a real show with better care.

Very few people keep their growing areas this warm in winter, which is why people think they normally drop leaves.

e.s.,

This is consistent with my observation of these plants. The extent of the leaf loss varies a lot. This may expain why some sources day they are evergreen and other say they are deciduous.


The yellowing of the lower leaf of the plant I photographed coincides with an abrupt drop in temperatures beginning with 95F highs/75F lows to 85F/65F over the last two weeks. It also went from sunny every day to heavy overcast. Night temperatures next week are forecast to drop into the high 50s. This is extraordinarily cool for this time of year in S. central Mississippi. I'm curious to see what happens. I may bring two plants indoors and leave two outdoors just to see what happens.


-Keith