Is This Rot?

[ChrisAZ]

This is about my Mandarin Sunset plant. She was doing beautifully all summer, even through our 100+ degree temps in Southern AZ. All my hibiscus stayed outside until late November, when we had a cold snap and I brought them inside. Then Mandarin Sunset started to get pale green leaves with darker veins that turned a sickly yellow green and then fell off. I moved the plant back outside for as long as I could, and that seemed to improve the her health, but when it got too cold to leave her outside any longer I moved her back inside, and she started looking sickly again. I was hoping she would hold on until spring so she could go back out. I made sure to never allow the soil to get too damp, and I had her in the brightest location I could put her but she slowly worsened throughout December before really taking a turn for the worst at the end of January. Now she's almost completely defoliated, and the tips of about half the branches have turned black or brown. I have been checking her for rot and today found a new soft spot right above the ground. You can see it in the pictures. Is this rot, and if so, is there anything I can do about it now, or is it too late? I lost my Time for Love from root rot last spring, and the pot MS is in now is the same pot that Time for Love was in when it died, so I'm wondering if it could be something about the pot?

Thanks,
Chris

The first pic is Mandarin Sunset back in October, the second is the soft spot on her trunk (I circled it in yellow), the third is what she looks like now, the fourth is a close-up of her remaining leaves, and the fifth is one of the blackened tips that I pruned off (the insides of the tips are tan mush).

[roadrunner]

Hi Chris

I can't help much with the your Mandarin Sunset issue, but am curious where you are located.  I live in Sierra Vista, AZ.  My collection is also inside for the winter and moved outside for the warmer months.

[farmer d]

Hi Chris - this time of year is tough for rot.  I have seen end of January as the peak time for rot to be most prevalent and problematic.  Do a scratch test on the bark just above that spot and see if the wood underneath is still vibrant bright green.  If so I would back off on any further watering until the plant shows signs of new baby leaves.  It could also just be unhappy with the winter conditions.  Maybe investing in a T5 grow light or two to provide not only light but much need warmth too might help.  Also if indoors it can get very dry so a quick misting of the leaves can help too but be careful to keep the trunk and soil from getting wet when spraying.

If you really want to go all out I recommend bare rooting your plant where you can observe the roots and maybe spot rotted ones.  Also my experience is that one of the most common places these plants get root rot is underneath the main trunk where all the roots start to branch out.  You can only see that if you bare root your plant.  It is risky if your plant is weak or diseased to do this as with a healthy plant it is very stressful to bare root.  But if you do you can also rinse the roots in a 10% bleach or soap solution to kill off those pathogens.  Use fresh new soil and also sterilize your pot and anything else like stakes or name tags as pathogens can be on them too and just start spreading again.

Farmer D

[ChrisAZ]

Thanks for your replies Roadrunner and Farmer D. Thankfully spring came early this year, and all my plants are back outside enjoying the warm weather. Mandarin Sunset lost the rest of her leaves, but she now has multiple new little baby leaves. I also cleared the soil away from the spongy part and have avoided getting the trunk wet, only watering the outer parts of the pot, and for now it's dried up. I did a scratch test and it still looks good. For future reference, what's the best method to go about bare rooting if this should happen again, or to one of my other plants? Next winter I'll definitely mist the leaves of my plants. Would that also help prevent a spider mite infestation? I have another plant that's recovering from that too. 

Thanks,
Chris

P.S. I'm in the Tucson area, north of River Rd. Casas Adobes area. Good to know there's another hibiscus collector near by

[roadrunner]

Hi Chris,

Sorry I didn't get back to you, been working on my other plant addictions, roses and daylilies.  I'm in Sierra Vista.  I'm still not convinced there won't be at least one more shot of cold for us down here at about 4600 ft elevation.  It's happened too many times in previous years.  I usually need to wait until mid to late April to move the hibs outside.

dave