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Odd rust color on the bottom of the leaves of this rubber plant?

Anyone know what this rust color on the bottom of the leaves of this rubber plant is?


I’ve been wanting a tricolor rubber plant for a long time, but it has this strange color on the bottom of some of the leaves. I don’t see any insects at all.


Is it due to cold exposure? It’s winter here, and it came from a grocery store. Not the best care.




Dark spots at left are dirt, not insects.





Thanks.

Comments (5)

  • 2 years ago

    How cold did that plant get? It's normal for the leaves to be bronze-ish on the back, but your pics do not look normal. There are some black flecks in the closeup pic but I can't tell if they are critters or something else.


    Some pics of various F. elastica plants with leaf reverse visible:

    https://garden.org/plants/photo/770010/

    https://garden.org/plants/photo/571603/

    https://garden.org/plants/photo/270611/

    https://garden.org/plants/photo/708128/

  • 2 years ago

    It's likely chill injury, which can occur along with a sudden drop in temperature even if the temperature does not fall below freezing (causes phenolic compounds to leak from plant cells into intercellular spaces).

    There is a high probability the leaves affected will be shed. That, in itself, is not a particularly big issue, but it's important that some other calamity doesn't cause a recurrence of significant foliage loss.

    Unless you have more questions/input, come back to see us around Independence Day. Depending on what happens between now and then, it might serve your plant well if it was pruned and defoliated (will force many new branches and leaves).

    A ficus, pruned and largely defoliated:


    6 weeks later:


    Tidied up a bit:


    You can see that pruning and defoliating accommodating trees at the right time is a good way to force branching and a new flush of pristine new foliage.


    Let me know if you want some links to help you with appropriate care.

    Al

    linnea56 (zone 5b Chicago) thanked tapla (mid-Michigan, USDA z5b-6a)
  • 2 years ago

    i want al's tool rack..lol ..


    ken

    linnea56 (zone 5b Chicago) thanked ken_adrian Adrian MI cold Z5
  • 2 years ago

    Tiffany, it must have gotten cold. It’s been in the 30’s here. Maybe it sat in a delivery truck too long. If I hadn’t wanted one of these for a long time, I’d have passed on it. There were 3, and all had this brownish tinge on the middle leaves. Bottom leaves and the top, newest leaf are unaffected. That’s part of the reason why I figured it might not be insects. I sprayed it with Neem oil as soon as I brought it home, just in case.


    The black bits are just potting soil. I should have brushed that off before taking pictures.

    It’s in a tiny 2 1/2” pot, which is not doing it any favors. Considering the plant is about 10” tall, I will be repotting it as soon as I can.


    Thanks for all the great information, Al. The topmost leaf and the bottom leaves are normal. It’s the middle ones that are brown.


    At what point should I remove some leaves? Let it adapt to being repotted first? Wait til spring? It would be nice if I could induce branching too.


    Thanks!

  • 2 years ago

    At what point should I remove some leaves? Light levels are a key element in how much stored energy the plant is likely to have and how much food it can make (a plant's true food is sugar, glucose - which it makes during photosynthesis), both of which should be at peak levels around the summer solstice (21 June in the Northern Hemisphere, where we live). The idea is to care for the plant as best you can, try to move it outdoors for at least several weeks before the solstice (you should be able to do that around Memorial Day), and make sure you're watering/ fertilizing appropriately. Good nutrition is essential to good vitality (health). An under-nourished plant can never be healthy.

    Let it adapt to being repotted first? I'm guessing you potted up as opposed to doing a full repot, which includes bare-rooting, root pruning, and a change of soil. If you potted up, there isn't any adjustment to be concerned about. As soon as you see new growth after repotting or potting up, your plant is "adjusted". You might need to be extra careful about your watering intervals because the plant is more vulnerable to over-watering in a larger soil mass. That "allow your plant to adjust to its surroundings" thing is way over rated and not grounded in science. When we bring a new plant home, it immediately adjusts to its surroundings. If unwanted symptoms are noticed, it's not because the plant is adjusting, it's because the plant doesn't like the cultural hand it's being dealt.

    Wait til spring? Yes and no. "Spring" lasts 3 months. Early spring (winter and late fall, too) is about the worst time to do heavy work like repotting, hard pruning, or defoliation on most houseplants. Those procedures should be done when stored energy and current ability to create energy/food is at peak, which is around the summer solstice. The reason is the plants metabolic processes are humming because energy availability is at peak. This means the plant recovers fastest from any heavy work you might do to it, and will be better able to defend itself against insects and disease pathogens. Doing hard work out of season makes the recovery period much longer, and that isn't necessary. Plants have natural rhythms. Learning to take advantage the plant's period of strength and making allowances for when it's weakest is much easier on the plant, and it will make us feel like we're better nurturers. Those of us who don't look at plants more like pets than decorations all have a nurturing bone that needs to be satisfied. Yes?

    It would be nice if I could induce branching too. Your rubber tree is a prolific back-budder, especially if you prune and defoliate a healthy tree at the right time. So get your tree healthy, and come back whenever you have questions, but especially come back in June so we can take another look. Here is one of my Ficus before and after defoliation:

    Ficus Benjamina w/fused trunk 2016


    After defoliation:


    2017 After partial defoliation, pruning and wiring:


    How the planting looked in 2007:

    Al

    linnea56 (zone 5b Chicago) thanked tapla (mid-Michigan, USDA z5b-6a)
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