Diseased H. lobbii

karyn1(7a)July 31, 2012

What the heck is going on with this H. lobbii? I noticed these spots a couple weeks ago. The plant is still growing well but I doubt that will last. Is there any way to save it? TIA

Underside of leaf

Top of leaf

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The spotting at first looked fungal but once I enlarged the photo it appeared to simply be reddish pigment. Do you have your Hoya lobbii in very bright light? These red,purple, or blue pigments are called Anthocyanins and they generally function to help protect leaves from excess light but are common in other areas of plants such as flowers. Many Hoyas also have reddish new leaves or the beautiful red leaves in sunlight (think Hoya obscura) and this is the same reaction. This is the reason I ask if your plant is in very bright light? Hoya lobbii can take bright light but not direct sun. I have mine about three feet back from a South facing window but it's near the ceiling so it gets no direct sunlight but very bright indirect light instead.


    Bookmark   July 31, 2012 at 11:20AM
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It's in bright filtered light, no direct sun. I hope that's all it is. My variegated hoyas in the same area are extremely colorful with lots of reds, pinks and purples. Should I watch out for anything or are you comfortable that it is the pigment? Thanks for your help yet again.

    Bookmark   July 31, 2012 at 1:06PM
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The spots are red if I am seeing them correctly right? If they are then it is a response to intense light. If you don't like the spots then move the plant to slightly less light, that's what I would do if this were my plant.
Fungal spots usually start as a dark spot and then they spread outwards as the fungi consumes the nearby cells. The tissue becomes yellow etc as the disease spreads. This is not the case with your plant so I am confident that this is not a disease.

On the subject of this type of response to light I would like to mention that although we often like the look of the Hoyas that produce colourful leaves it is not always desired, it can be overdone. This is a response by the plant to reduce the amount of or a articular wavelength of light being absorbed by the leaf. Many Hoyas would show this response seasonally during the stressful dry season when deciduous trees drop their leaves and water is scarce. During the rest of the year when conditions are better for growth the plants may well appear all green.

I would recommend reading the article I linked to just so you understand a little more about this function in plants.


Here is a link that might be useful: Anthocyanins in plants

    Bookmark   July 31, 2012 at 1:53PM
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I know the function of anthocyanins in deciduous trees but never thought about it in relation to other plants. I'm just used to my succulents and hoyas coloring up significantly when I have them outside in natural light as opposed to grow lights indoors. Thanks for the link. I'll take a look.

    Bookmark   July 31, 2012 at 2:39PM
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