Someone help, plzzzz! Did some more reading and it looks like we weren't watering it enough... Are they supposed to be drenched each watering (enough water to run out the drainage and into the pan)? Expert advice would be much appreciated :)

Any changes recently that would have caused the plant some stress?

I water the plant twice a month (during the winter months--Nov. thru now) (about 1 liter/34 oz tap water left to sit for a day or more due to calk concentrations in Berlin's tap water) (is this enough water??). The plant sits in a pot with holes/drainage...

How do you currently judge when the plant needs to be watered? When you do water, what is your method? Are you familiar with using a chopstick or dowel to check when the plant needs water? You should water when it needs it, not on a schedule. If not familiar I can post what Al (Tapla) has posted previously and that will help you a lot.

-fertilizing (since it is still winter here, instead of giving it a full dose, we gave it a half dose of fertilizer)

Which fertilizer are you using and at what dose?

-moving it to a sunnier spot (its lower leaves were drooping-->we read this might be due to a lack of sunlight)

What direction does that window it is in now face?

One other thing to note is that the plant has some spindly roots growing out of its pot (you can see this in one of the pictures I'm attaching). Is this a sign that there's overcrowding and we should replant it in a bigger pot?

That soil looks quite moisture retentive, and the plant appears pot bound - Those look like roots trying to run out of the pot, a repot in the summer is due. Wait until June if you can, that's the optimum time for us folks north of the equator.

Plants are reactive organisms, so we can be sure there's a reason the plant is showing it's dissatisfaction with one or more of the cultural conditions that are affecting it now or have in its recent past. Your job, my job, every grower's job ........ is to figure out what the negative influences are, and correct them. Once you've done that for every plant, you'll have the happiest plants on the block.

Plants are genetically programmed to tolerate some degree of stress. The amount of stress plants can tolerate from species to species varies significantly more than what the lions share of plants want. If you eliminate cacti, half of the succulents we commonly grow in pots, and carnivorous plants, you'll find the other 90% + of plants all pretty much want the same thing - a well-aerated soil that holds enough water to satisfy moisture needs but not so much root function/health suffers, watering at appropriate intervals, the right light/temperature levels, a good nutritional supplementation program, and reasonable ongoing care over the long term. This means that the overwhelming % of plants all prefer pretty much the same type of treatment.

Stress occurs when plants are growing at or near the limits they are programmed to tolerate. Too much stress leads to strain, which always ends in death of the organism, unless corrected. While they will tolerate some stress, it's bad form to test their limits. A plant's systems are like a rapidly spinning top. Everything seems to work in harmony until something acts to produce an imbalance. If the imbalance is severe, the top can go spinning wildly out of control and collapse. Plants, too.

I'd probably place a small wager on the cause of yellowing leaves being light-related, as in lack thereof, but there are other factors that can cause the yellowing foliage, which isn't presenting as a nutritional issue would.

It's highly likely you'll find the clues that can help you figure out what changes would benefit your plant in this thread about The Basics of Growing Well in Containers.

Al

The plant is too close to the radiator. As you have noticed yourself, it started shedding leaves not long after the heating started (in December).

At the very least, for the winter I would put it on the table, above the level of the heater and as far away from it as possible. Since it needs light so you will have to make judicial decision yourself how far. The farther from the heater the better, the farther form light the worse :'‑( . It will not recover the lost leaves and it will lose the yellowing ones, but at least Fergus's condition will stop deteriorating.

As for watering you should water slowly but thoroughly, until a little water will show in the saucer at the bottom of the pot. The water should never "run " out of the drainage hole. There is no need to flush the soil each time when watering (unless you over-fertilize!).

Is there any chance that water collects in the outer pot? The seems a fairly tight fit & occurs to me as a possibility (tho' the top does look rather dry).

Everyone: Thank you so much!

The dropping has slowed down somewhat, so we're making some progress... This may be due to the fact that we are slowly regaining normal levels of sunlight--whew! I have made some changes in my care for Fergus and appreciate your tips very, very much.

I am not sure how to reply directly (the "@" does not seem to be working and I don't see a "reply to" option on each comment...)...

@J Williams--yes, the roots are busting out. As Treegeek Z6a suggested, it may need to be repotted. I will try to hold off until June, as suggested... But to answer your question: yes, they are busting out.

@Treegeek Z6a: Re: changes that would have caused stressed: No! I moved it to a sunnier spot, but only after it started dropping a lot of leaves... I can't think of any changes that would have caused the leaves to drop.

Re: watering: I currently check for moisture by sticking a finger into the soil. I have read that the top 2-3 inches need to be dry before watering... do you think this is correct? Should I step up my game and use the methods you describe (nope, I'm not familiar with them!). Would appreciate your input & being able to take a look at the instructions by Al that you describe!

Re: fertilising: I have stopped fertilising the plant for now. I was using a generic fertiliser described as "universal fertiliser for indoor and balcony plants." It is mineral and contains all "staple nutrients." (Sorry--it's in German, so I'm translating it.) It contains boron, zinc, iron, phosphorous, etc. I was following the directions on the bottle--1xmonth in winter months, 1/2 per 2 Liters of water.

Re: repotting: I will wait till the Summer to repot--thank you for ID'ing the repotting need!

@tapla: Thank you so much! I have taken a look at the page you linked. I appreciate your response.

@windberry: Thank you for your tips! I have kept your watering instructions in mind while watering Fergus and I am looking for something to place him on top of! Unfortunately, all of our windows have radiators by them... I have turned the radiator by Fergus off and hope this will help.

@karen S.: I don't think water collects in the outer pot... But I have been keeping an eye on it and will continue to do so!

" I have turned the radiator by Fergus off and hope this will help. "

It is the best thing you could do. Ficus elastica is a rain forest plant and will not perform well in too dry environment. This applies not only to the top but to the roots, as well. The soil in the pot should be consistently moist, but not overly wet. To ensure that, I recommend watering from the bottom, not from the top. Just pour water in the saucer at the bottom of the pot and let the soil absorb as much water as it will. If the water is sucked up too quickly add more. After fifteen minutes to half an hour discard remaining water from the saucer. Moving the plant to a bigger pot would help to ensure the soil is consistently moist.

The extracellular cuticle that covers leaf surfaces is composed of an insoluble polymer (cutin) and soluble cuticular lipids (wax), which work in concert to form a particularly effective barrier to transpirational water loss in F elastic. While there would be no reason to look for radiators to place your rubber tree in front of, radiators don't have the same inherent potential to stress plants that forced air heat vents have, unless you set your plants on or directly above the radiator. A radiator heats air that rises, as it rises, it creates a negative pressure that pulls the coldest air in the room, which is at floor level, toward it. As the air passes over/through the radiator, it warms and rises. This creates a gentle convective current that actually bathes the plant in cooler air. If you sit in front a radiator, you can't feel the warmth from the radiator, but you can feel a cool draft moving across the floor toward the radiator.

I wouldn't recommend watering from the bottom. It's much less effective at eliminating excess salts from the soil, and it doesn't force unwanted soil gases (CO2, methane, ....) and pull oxygen into the soil as it flows downward. Once water moves through the soil and makes it's way into a collection saucer, there should be no pathway by which the effluent can make its way back into the pot. Plus, not all soils are suitable for wick watering. For instance, I grow nearly all my plants in the gritty mix, and if I depended on wicking to moisten the soil, I'd be in deep trouble.

Most off the shelf soils hold an excessive amount of water, such that when the top 2-3" of the soil feels completely dry, the bottom 3-6" or more can be 100% saturated. Rather than use a digital moisture detector (a finger), you might try using a 24" piece of wood dowel rod as a 'tell', to help you get a better feel for what watering interval is right. You can buy one for a buck or less at any hardware. They're usually 48" long - cut it in half and sharpen all 4 ends in a pencil sharpener and they'll last a long time. You'll be surprised at what you discover about how often you'll need to water. I'll leave something I wrote about using a tell below.

There's a thread about growing Ficus in pots that you might find interesting; and, if you want to read about long term care of plants in pots, which includes information about repotting and root pruning, this thread about long term care of trees in containers will provide a lot of info.

Using a 'tell'

Over-watering saps vitality and is one of the most
common plant assassins, so learning to avoid it is worth the small
effort. Plants make and store their own energy source –
photosynthate - (sugar/glucose). Functioning roots need energy to
drive their metabolic processes, and in order to get it, they use
oxygen to burn (oxidize) their food. From this, we can see that
terrestrial plants need air (oxygen) in the soil to drive root
function. Many off-the-shelf soils hold too much water and not enough
air to support good root health, which is a prerequisite to a healthy
plant. Watering in small sips leads to a build-up of dissolved solids
(salts) in the soil, which limits a plant's ability to absorb water –
so watering in sips simply moves us to the other horn of a dilemma.
It creates another problem that requires resolution. Better, would be
to simply adopt a soil that drains well enough to allow watering to
beyond the saturation point, so we're flushing the soil of
accumulating dissolved solids whenever we water; this, w/o the plant
being forced to pay a tax in the form of reduced vitality, due to
prolong periods of soil saturation. Sometimes, though, that's not a
course we can immediately steer, which makes controlling how often we
water a very important factor.

In many cases, we can judge whether or not a
planting needs watering by hefting the pot. This is especially true
if the pot is made from light material, like plastic, but doesn't
work (as) well when the pot is made from heavier material, like clay,
or when the size/weight of the pot precludes grabbing it with one
hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok
for shallow pots, but not for deep pots. Deep pots might have 3 or
more inches of soil that feels totally dry, while the lower several
inches of the soil is 100% saturated. Obviously, the lack of oxygen
in the root zone situation can wreak havoc with root health and
cause the loss of a very notable measure of your plant's potential.
Inexpensive watering meters don't even measure moisture levels, they
measure electrical conductivity. Clean the tip and insert it into a
cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a
planting's need for water is using a 'tell'. You can use a bamboo
skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm)
would work better. They usually come 48” (120cm) long and can
usually be cut in half and serve as a pair. Sharpen all 4 ends in a
pencil sharpener and slightly blunt the tip so it's about the
diameter of the head on a straight pin. Push the wooden tell deep
into the soil. Don't worry, it won't harm the root system. If the
plant is quite root-bound, you might need to try several places until
you find one where you can push it all the way to the pot's bottom.
Leave it a few seconds, then withdraw it and inspect the tip for
moisture. For most plantings, withhold water until the tell comes out
dry or nearly so. If you see signs of wilting, adjust the interval
between waterings so drought stress isn't a recurring issue.

Al

Al said it all, heed his advice, you wont regret it. :)

@tapla: Al, thank you so much for the tips and explanations. It is all starting to make sense to me. Your explanations are also super engaging--I'm happy to be learning so much! I will definitely rely on the Ficus in Containers and Trees in Containers threads going forward. Regarding the tell--I will use one starting today! I had read all over the Internet--most articles about rubber trees include it--that the 2-3 inch trick (finger test) sufficed, but I can absolutely see why this would be misleading... Now that I know, I will pay closer attention to the bottom layers of soil. Thank you again--I really, really appreciate the help! (Oh, one more question for you: Do you agree that the plant seems to need repotting (in the Summer months, or sooner)?) Best from Berlin!