I just started getting some yellow leaves on a couple of my hib's. All different patterns too. Some all yellow, some spots, some veins. And some with all 3 on the same plant. I took some photos to show. I went out with my 20X mag and looked them all over and over for the past 3 days and see nothing crawling. Belle has some warty looking dark forms on her underside of the leaves though. But other then that, everyone is super clean. Some small spiders on them, but I leave them alone.
I feed with the HVH formula each Wednesday. 2 Wednesday's ago I added some seaweed plant food to the mixture. Then a couple days later I added a 1/2 teaspoon of Epsom salts on top of the soil (which would be my second time doing so this summer). Do you think one of these new additives might have done this? I hope it is not bugs, as I just brought them all into my office in preparation for Hurricane Earl...
Did it just happen since you brought them into your office? Hibiscus can be a bit temperamental when you make sudden changes in their conditions. The other things that I've seen cause yellowing leaves like this are repotting/transplanting, too much water, and inconsistent watering (common in the summer when the pot dries out a lot, then you drown it with water, etc). The good news is that while the yellowed leaves will fall off eventually, it's not permanent damage and the plant will grow new ones.
My guess is that it's a water issue. Even though it's still warm up there, the days are now getting shorter. With less an less daylight hours the pots tend to not dry out as fast. You're also getting some cooler weather "here and there" now. That also slows down the evaporation process. When you're thinking of watering them just pick up the pot and see if it feels light in weight. If it still feels a bit heavy/damp don't water them.
The issue with "Belle Du Jour" may be a black spot leaf fungus that can develop as the weather cools. It usually forms due to the foliage remaining wet and not drying out as fast as it does during the summer. I typically have that issue on some of my plants during the winter here in South Florida. There isn't much I can do about it since morning dew forms during the winter here and the foliage gets wet. Luckily the fungus is harmless, the weather warms up in spring and the foliage begins to dry off faster. Try not to get the foliage wet if you're watering in the evening. If the plants are close together, space them apart a bit more so you get better air circulation. That should help somewhat. I'm sure the issue will take care of itself once you bring the plants inside for the winter.
Liz, This happened a couple days ago. I just brought them in today for the hurricane we are supposed to get.
Jon, I was treating Belle with the late night hosing for a while for that mite problem I did have a couple weeks ago. It seemed to have worked really well. I check all the time for mites because I hate them.
I was cool for a week 2 weeks ago, and I only watered once that week. Then last week it became in the 90-100º again. I forgot about them for a couple days and one morning they were really dry and drooping. Saffron, Cindy, & Voodoo showed the worst of it. Then I of course took the hose and drown the heck out of them! Is that a Oops? I'm still learning...
I'd guess it's the drying out then drowning--I do that to mine (accidentally) at least a couple times a summer and they always recover, so as long as you try to avoid doing that all the time I wouldn't worry to much.
It was probably the late night hosing that caused the black spots/leaf fungus on "Belle Du Jour". The foliage isn't going to dry as fast overnight in comparison to daytime.
I let mine dry out quite a bit before watering them. Not all that uncommon for me to see some wilting on the newest foliage before I water them. Even in the middle of the summer I only water my container plants every 2 days. In the winter it's every 3-4 days. The sprinklers water the hibiscus in the ground every Wedn and Saturday morning for 12 minutes. I no longer give the "in the ground" hibiscus any additional waterings and they seem to be fine with that.
I'm sure we all get yellow leaves from time to time. It's just part of the natural cycle since each leaf isn't meant to last forever. Down here it's common to see yellowing foliage when the seasons change. It happens when we transition from drier winter weather to humid summer weather and then happens again in the fall when the weather become cooler and less humid again. There isn't much that can be done about it. You just let nature run its course.
You both have been so helpful. Thanks so much. Jon, I thought I was supposed to do the hosing for mites at night? Because you don't want to do it in the sun? I would much rather do it during the day, and not when I get home from work at midnight...
It is defiantly something I did to them. Liz is prolly right with the super drying and drowning. I normally don't water them but every other day in the summer.
You can do the hosing early in the day or in the evening. Generally you stay away from doing it midday so you're not burning the foliage. My personal preference is watering/spraying early in the day. That way the foliage has all day to dry. Not too wild about wetting any type of plant foliage in the evening. Much higher liklihood its going to remain damp during the night and develop fungal problems and/or powdery mildew.