I have a new rubber tree plant in my apartment. I got it almost three weeks ago. I don't know how old it is, but currently it's a little over 2 1/2 feet tall. For the first two weeks I had the plant, it was growing well. A large dark green leaf would open every 4 days or so with a long red sheath already inside of it. Several days ago that started to change. The leaves appear to be opening prematurely now. They are smaller and a light greenish-yellow color. Also, what used to be large red sheaths are now an inch or less long when it opens. I don't know if it got too much light or if I watered it incorrectly or what. Do you know what might have caused this?
Rubber Tree Growth Question
Sorry, meant to make a correction, and it submitted instead. I meant to say that if the soil is slightly damp, it will stick together when you squeeze it, but fall apart when you touch it. No water will appear when you squeeze it.
I also wanted to add that you might want to leach the soil to get out whatever high levels of fert might be in it. That means run a volume of water through the soil equal to about 5X the volume of soil.
If you got it 3 weeks ago, presumably from a plant store, it is a plant fresh from the grower. A new leaf every few days is quite extraordinary, indicating that it was probably pushed by the grower with heavy fertilizing, high light, and possibly other growth-enhancing procedures (gas, hormones, etc.). Now you take it home and its conditions are way different. Top of the list, the light has become much lower; that's OK, a plant that grows a new leaf every 4 days is going to be through your ceiling in a few months. Frankenstein plant.
Rubber trees can adapt to fairly low light conditions indoors. The critical factor is the amount of moisture in the soil. If it's in high light (plant is in front of a south or east window), you can keep the soil "slightly damp," that is, if you pull up a spoonful of soil from well down into the pot, and squeeze it between your fingers. There should be no visible water coming out as you squeeze it.
As the light level drops, you should allow the plant to reach a higher degree of aeration, in other words, when you reach a low light level, the soil when you squeeze it should not stick together, and should have only the barest trace of moisture.
As you have this plant longer, a more normal rate of growth would be a new leaf every 2 - 4 weeks. And make sure not to keep it too wet. Rubber trees that are too wet will show a reduced rate of growth (like a new leaf every 6 months), and small leaves when they do appear.
It sounds like the plant isn't getting enough light. Rubber plants can tolerate full sun outdoors, but prefer bright light. They need water enough to keep the soil on the slightly dry side of evenly moist.