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After killing my last rubber plant through over watering, I've been very careful not to do the same. So much so, that I came back from holiday to find all the leaves drooping. I watered it but a month later the leaves are still falling off every day! I'm watering from the bottom so the soil at the top still feels quite dry. Is it getting enough water? What should I do!? The top leaf has never perked up since I underwatered it! When I put my finger down through the soil it doesn't feel very compact at all![enter image description here]1

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Depending on the type of soil you used and how much water you are giving through the bottom it may not be enough. If it is very well draining soil it will have a more difficult time absorbing water beyond a certain point, even sitting in water all the time. The water has to travel up, against gravity.
The other is how much water are you giving. Do you keep giving it water until it stop absorbing water, or just give it a portion of water, like a cup.

The best thing you can do is invest in long bamboo barbecue skewers. Insert the skewer into the soil. Wait 30 mins or longer then pull it out and look at how wet the soil actually is. From that stick you will know when to water. You will also know how deep you need to make your watering tray for it to absorb water.
If it a typical peat and perlite or coir and perlite mix, you will not need that deep of tray, but you will need to wait 10-15 mins for it to absorb water, before you dump the tray out. In 5-10 mins check your skewer, it may have absorb water quite fast. If it is only absorbing water part of the way up the pot then you need to add more water, making it deeper easier to absorb. It does not need to get to the top of the soil. It just need to cover the roots. Leaving the top dry cuts down on possibility of fungus gnats. You do not want to leave it in the soil too long, then it will absorb too much water. You do not want to water log the roots of your plant.

You can stake up that leaning limb with a bamboo or covered metal stick.

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  • Thanks for your message. I usually sit the plant in the sink for half an hour so it can soak up the water and then leave it on the draining board to allow the water to drain before putting it back in the pot. I also have a layer on stones in the bottom of the pot to help futher draining. I'm just worried about over watering it. Do you think the leaves are falling off due to the lack of water a month ago? Dec 14, 2019 at 14:18
  • Use a bamboo skewer. It will tell you if you when to water. Also read this article on gravel on the bottom of your pot, its actually at myth that rocks on the bottom help with drainage. If you feel the need to remove the gravel, wait until spring to repot. Falling leaves now, it probably a problem happening now. Dry leaves tend to fall off when they are dry or dry up then fall off. deepgreenpermaculture.com/2019/09/06/…
    – GardenGems
    Dec 14, 2019 at 17:58
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I'm guessing you need to do these things:

  • Fertilize the plant (I'm guessing it ran out of nutrients; plants can tend to lose leaves in this scenario; that's exactly why those Christmas Poinsettias lose their leaves so fast: it's not because they're tempermental; however, those Poinsettias need like all the nutrients: not just NPK; Miracle Gro, wood ash, and Epsom salt are probably enough for those poinsettias, although I gave mine more things than that initially, such as monopotassium phosphate, iron, etc.; not sure about your rubber plant; rubber plants may be more sensitive to alkaline substances like wood ash than Poinsettias, so I'd be careful there, and only give it a couple pinches to see if it helps)
  • Water from the top (if the only thing that is wet is the bottom, the plant probably won't be getting many nutrients from the rest of the pot, especially with the sun drying out the top, plus, you run the risk of the leaves curling and getting fungal spots, if there's water pooling in the tray)
  • Water less at a time, but more frequently (don't let the water pool at the bottom)
  • Potentially give the plant a somewhat bigger pot (not a lot bigger).

Low light is another potential cause of leaves dropping, but your plant appears to have plenty.

With the kind of light the plant is getting, it's probably thirstier than if it were in lower light.

Edit: I tried wood ash since I wrote this answer. My personal rubber plant (in a 20-inch pot) was fine with a dose of wood ash (more than a few pinches, but not loads and loads); I did that combined with some Miracle Gro fertilization (24-8-16), watering it with less water at a time but more often and giving it more light, and that really spurred on a lot more growth. Whether or not the wood ash contributed, it sure had a better response to it than it did to basalt rockdust (don't use that on rubber plants). The reason I suspected rubber plants might be alkaline-sensitive is because of the poor response to basalt rockdust years ago. As wood ash is alkaline, I don't think that's the problem. Maybe it was the insolubility of the rockdust, maybe there was a pathogen in the rockdust, or maybe it was the wrong nutrient profile. The reason I was willing to try wood ash was because of the positive effects on other houseplants that basalt rockdust didn't give (and I had a hunch fertilizing with nitrogen more would help the plant use more calcium if things went sour).

I water mine from the top every 1, 2 or sometimes 3 days with the leftover water from our electric tea kettle from the day before (the water that didn't make it into my herbal infusions); it loves that. I used to give it a gallon of water every month or so; that eventually led to curled, spotted leaves whenever water pooled in tray; so, I switched to a half a gallon, but it was slow growing and still borderline too much for the leaves; but later switching to less water more often made a night and day difference.

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