Also, the reason the plant gets in more trouble when the radiator is on is that the heat dries the soil even faster. The solution to that is simple: be more vigilant in the winter about watering as soon as the soil is dry.

BTW, you have my complete sympathy about overactive radiators. My apartment is too warm from October through April because the walls and floors around the radiators get hot even when all of my radiators off, so I use fans to bring cool air in pretty much all winter. Grr!!

Cold drafts are hard on any of the tropical ficus; and getting your watering under control shouldn't be that hard. You can buy a 5/16" wood dowel rod, cut it in half, and sharpen all 4 ends in a pencil sharpener. Push the rods deep into the pot. If it comes out wet or stained dark, don't water.

I'm not sure you're under-watering. I say that because the attitude (a word used to describe spatial positioning) of the plant's leaves looks pretty normal. If you're under-watering to the point of drought stress severe enough to cause leaf abscission (shedding), you will have had wilting of leaves which changes leaf attitude. Usually F lyrata doesn't full recover such that it returns to its former attitude/spatial position. IOW - even after the plant regains full turgidity, the leaves should still look at least a little 'droopy' in comparison to their former attitude. You'll have a better idea of whether you were over or under-watering once you start monitoring your plants soil moisture.

I'd also enthusiastically suggest you work out a plan that allows you to flush the soil at regular intervals, and that you fertilize at regular intervals. More help on that if needed, but let's see what you think about what you've heard so far.

Al

Thanks for the correction, Al, I just found it confusing.

Not a correction, alternate theory, L. I might be the one who's wrong. Just trying to put 2+2 together. If the OP says the plant was definitely under-watered, it sure would account for the plant's bout of pouting.

Al

Thanks for chiming in with some considerations!

I will get some dowels so I can monitor the moisture a bit more closely. The way I have been monitoring it, is that there are several large holes on the bottom of the container. I can reach my fingers in and feel if the soil is moist at all. It takes at least 2 weeks for the moisture at the bottom to dry up. I can't remember exactly now, but I think toward the beginning of getting the tree I gave it maybe half a gallon when I watered it and it didn't react well. Since, I've been timidly giving it about 1/2 - 3/4 of a liter every 2 or 3 weeks and it retains moisture in between - which really seems like a crazy small amount of watering.

Also, the leaves have never drooped (Al - I think that is what you mean by attitude?). That's part of what seems strange to me, is that they look normal and suddenly drop with no warning.

Hope this helps! I can post a picture of the soil - if that would also be more helpful - tomorrow when I have better lighting.

Thanks again!

Oh, a little more on the question of under watering. What has happened is that I went a little longer than usual before watering (didn't check through the bottom to feel for moisture, but I'm sure it was dry). However, the tree hadn't changed at all in appearance or dropped any leaves until a couple of days after I watered it. It was also exposed to an open window/radiator situation the day that it started dropping leaves, so it's hard to tell which could be to blame.

So the radiator and breezes have been an issue every time it's dropped leaves? Sorry I didn't catch that. Still, knowing what's going on in the soil in response to your watering while keeping everything else the same will tell the smart people around here something about what's going on. You never know which clue will help solve the puzzle.

The only plants I've had that dropped healthy looking leaves were my scheffleras in the last few months before I flushed them and gave them diluted fertilizer and a lot more light, at which point they simply stopped. They had stopped growing and hadn't had good light or fertilizer for a long time, and the water here is pretty hard, but they turned around really quickly, so I assumed that they'd been suffering from all kinds of problems.

I believe flushing the soil in particular had an immediate effect even though the scheffleras were still in water retentive soil that hadn't dried out in a few weeks. They really perked up after I washed away the mineral deposits and gave them a diluted solution of fertilizer. No doubt it helped the roots take up nutrients and moisture once their water wasn't saturated with nasty hard water deposits.

Good luck!

There are inherent limitations in a soil that takes 2 weeks to dry down to the point the grower feels it's safe to water again. We have to allow too, that since you haven't been monitoring moisture levels, the plant might be capable of going much longer between waterings, which would tend to increase the level of limitations associated with too much water in the soil. Given the size of the plant and the size of the container, the only way that can occur is by virtue of the fact the soil holds a lot of excess water. The soils I use require watering every 1-4 days, depending on the pot size and weather or indoor conditions. Keep in mind that most of my plantings are bonsai, so the ratio of plant mass to soil volume is very different than growing in a container as large as yours. I do have many dozens of plants growing on for bonsai in containers the size of the one you pictured and much larger, however. I think plantings that actually DO require watering every 2-3 days probably represent the best opportunity for plants to realize as much of their genetic potential as possible, but you'll need to decide weather or not you're willing to work toward getting to that point and subsequently making the effort it takes to water that frequently.

Since we might never know what caused the leaf drop, it's probably best to confront the issue on several cultural fronts. My plan for the plant in the short term would be to take steps to significantly reduce the volume of excess water your planting can hold. That can be done in a variety/combination of ways. I'd see what I could do about getting it more light and maintaining a constant temp of about 70* or warmer. I'd flush the soil at regular intervals and fertilize regularly. Unless there are other potential limiting factors we don't know about, these suggestions should allow your plant to recover.

Because the above doesn't go into a lot of detail doesn't mean I can't. If you're up for making the effort, you'll get all the help you need, a good part of it in the form of homework I'll link you to. After you read it, ask about anything it leaves you wondering about.

Al