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

last year

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)

Tiffany, purpleinopp Z8b Opp, AL
last year
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/
tapla (mid-Michigan, USDA z5b-6a)
last year
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)
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What Lenore said, plus: Container plantings need regular fertilizing. If you don't fertilize regularly, plants will take to cannibalizing its existing parts (leaves and branches) for mobile nutrients, then shedding them. "Mobile nutrients" are those that can move from place to place in the plant and includethe nitrate form of nitrogen, phosphorus in phosphate form, potassium, and magnesium, but chlorine, zinc, and molybdenum, are also mobile or partially so. Calcium, sulfur, iron, boron, and copper, are considered to be immobile.These nutrients must be present in the nutrient stream at all times in the plant is to grow and function normally. When a leaf is cannibalized of nutrients to fuel new growth, it is shed. The appearance of new growth at branch tips and new leaves doesn't necessarily mean the plant is growing. Growth is a measure of the plant's dry mass, so if a large leaf is shed and a small leaf or two appears, it can actually represent a step backward and a symptom of decline. Tight roots also have a strong influence on the volume of leaves the plant can retain. Badly rootbound plants are very often conspicuous in that foliage tends to concentrate primarily at the growing tips of branches, giving many plants a poodle or pompon look. On top of all that, over-watering and/or under-watering and/or a high level of dissolved salts (from fertilizers and/or tapwater) can work individually or in concert to cause a drought response which leads to leaves being shed. Let me know if you find value in what this links you to, please. I think it's a good time to formulate a plan you can work on between now and next June when you repot into an appropriate soil, one that allows you to water to beyond saturation w/o having to worry that an extended period of soil saturation will inhibit root function and wreck root health, which it WILL do if not guarded against. If you want help putting that plan together, let me know. Edited to say: Looks like you have several links to explore. LB and I were typing at the same time. Al
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Overexposure to sun affects plants differently than people/animals. In plants, overexposure causes a hyper-excitement of molecules in the plant's epidermal layer. As the molecules return to a less excited state, they release the same O- free oxygen radicals that are found in H2O2 (hydrogen peroxide). These free radicals attack pigments that are most susceptible to exposure, primarily chlorophyll, and oxidizes the pigment molecules. It actually bleaches/oxidizes the pigment by way of the very same mechanism that H2O2 bleaches hair, which is why the scientific name for sunburn in plants is photo-oxidation. The most common result is an initial gray or silver appearance of affected tissue that soon turns brown or black. You should look to something other than sunburn for the cause of the pinkish coloration. Sometimes a P deficiency can cause expression of the pigment anthocyanin, but a P deficiency is not the only suspect cause of purple leaves. Nearly any environmental condition that puts the brakes on growth (and the accompanying use of food (sugars), but does not limit sugar production (photosynthesis) can cause anthocyanin buildup and purple leaves. Very often too, when the more central part of the leaves are purple, an overly high level of Ca in the soil can be the suspect. Soil saturation also blocks uptake of P and Mg, which in concert can cause expression of anthocyanin in leaf tissues. Al
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It looks like residue from insecticide or fungicide applications; or, early on, the plant was in a situation where it was watered from overhead and the water was allowed to repeatedly dry on the foliage, leaving dissolved solids residue on the foliage. It's possible too, that the same chemicals mentioned above were injected into the water used for over-head watering and were left behind on foliage as the water dried. I don't think it's cause for concern. If it interferes with the plant's ability to carry on photo synthesis, chemical messengers will inform plant central the leaves aren't carrying their weight, and the plant will automatically shed them. Too, your plant looks healthy enough that removing the affected leaves shouldn't create a scenario where the plant is using more energy than it's creating by turning the sun's energy into food ..... so you can remove them w/o need to be concerned. Remove them by snipping through the petiole (leaf stem) about half-way between where it's attached to the stem and where it transitions to the leaf blade. The stub you leave will fall off on its own in a week or two. Pulling leaves off can easily damage latent buds resting in leaf axils (angle formed by a leaf and the branch it's attached to). Al
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The leaf surface with the lightest variegation is indeed more susceptible to sunburn. The pigment chlorophyll functions as though it's nature's sunscreen for plants, and the lighter parts of the leaf have much less chlorophyll, so there's more potential for burn. I'd considered sunburn as a potential cause, but discounted it for a couple of reasons. Rachel said her plant was in a state of quiescence and had just started to grow new leaves. She also didn't indicate it was moved into a considerably brighter spot. Any leaves that existed on the plant prior to any new foliage would have already been conditioned to where the plant is sited; and, any new leaves that come into existence would be perfectly adapted to the photo load wherever the plant is sited. Too, many symptoms related to other issues tend to show up in the lighter parts of variegation, notably, over-watering, a high level of dissolved solids in the soil solution, and toxicities of one or more elements/compounds, particularly fluoride which I don't suspect to be the issue here. Given the info Rachel provided, I'd bet the plant was struggling because of too much water/not enough air in the soil, which limits the plants ability to take up and move water efficiently. Increasing the EC/TDS level of the soil solution by adding fertilizer salts further decreases the ability of the plant to make efficient use of water in the soil, which yields a plant potentially dying of thirst in a sea of plenty ...... at least until the issues are fixed. As an aside, I have a variegated F benjamina forest (a bonsai group planting with more than around 9 trees is referred to as a forest planting - fewer trees are a grove or clump planting) with 15-20 trees in it. It sits on a nursery cart on a cement slab in full sun from dawn until around 7PM and there is no sign of sunburn on any of the leaves ...... but that's not to say the leaves can't burn. They can and the lighter areas will prove more sensitive, just as you suggested. Al
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ken_adrian Adrian MI cold Z5
last year
i want al's tool rack..lol ..

ken
linnea56 (zone 5b Chicago) thanked ken_adrian Adrian MI cold Z5
linnea56 (zone 5b Chicago)
Original Author
last year
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!
tapla (mid-Michigan, USDA z5b-6a)
last year
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)

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

Comments (5)

Tiffany, purpleinopp Z8b Opp, AL

tapla (mid-Michigan, USDA z5b-6a)

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

Comments (5)

Tiffany, purpleinopp Z8b Opp, AL

tapla (mid-Michigan, USDA z5b-6a)

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ken_adrian Adrian MI cold Z5

linnea56 (zone 5b Chicago)Original Author

tapla (mid-Michigan, USDA z5b-6a)

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linnea56 (zone 5b Chicago)
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