An important factor in determining the suitability of a plant to your home and envisioning the care it will need, is to know the origin of the plant. Pilea peperomioides is native to damp, rocky areas of China. Like many houseplants, the pileas that we grow at home are relative babies and we give them the conditions that maintain the cute, compact form of an immature, newly growing plant. That includes protecting them from harsher elements of cold and draft while allowing them the free draining soil and moisture of their native habitat.
Pilea will live in semi-shade but bright, indirect light, a short distance from a window is better. Avoid direct sunlight. The main shoot naturally divides into side branches, and dense growth is usually automatic on a young plant. With lower light levels, the plant will be leggier and leaves will be more spread out. You can nip out over-long shoots from time to time, balancing growth. Turn the plant a quarter turn each time you water it to encouraging symmetry.
Pileas do not have a large root system and do not like overly wet conditions, but appreciate humidity. When watering do so sparingly, but moisten all the soil, with room temperature water. Let the top two-thirds of the potting mixture dry out before watering again. Remove run-off water after it drains. In winter, your pancake plant will be in a non-growth phase and will require less water.
Your pancake plant may be kept in a shallow container, but it must have a drain hole. Keeping a layer of pebbles at the bottom of the container will not replace the need for a drain hole. Water vapor from the water held in the rocks beneath the soil keeps it too moist for the delicate roots.
You can add humidity to your room by placing the plant container and its run-off dish on top of a tray of wet pebbles. The water will evaporate up into the leafy area of the plant from the high surface area of the pebble tray.
Normal household temperatures, in the range of 65 to 80ºF., are good. Do not let the temperature fall below 55ºF. and move the plant away from the cold micro-climate near the window in winter chill. Protect it from drafts, from air conditioning vents, open windows and heat vents.
These plants have a small root system and do fine in a 3 to 4 inch pot, with a mixture of soil-based potting mix and peat. Your plant may become leggy and unattractive before you need to re-pot it. You can take a tip cutting in late spring to propagate a new generation of pancake plants.
Feed in spring and summer only, with a balanced organic fertilizer, used every other week at half strength.
Leaves need to be wiped regularly with a damp cloth. Without this care, the accumulating dust interferes with photosynthesis and your plant will behave as though it is getting too little light. Do not use polishes or oils which will build up on the leaves and create more of a light block.
Yellowing leaves are common and may be due to overly wet conditions, particularly if stems are also soft. Leaves also become pale if overexposed to light. Lower leaves yellow as they age naturally and prepare to drop.
Leaf drop can occur in the fall and, if serious, means that the environment is too cold and/ or the soil is too wet. Move your pancake plant away from the cold micro-climate near a window where the temperature can be significantly colder than the rest of the room. Your Pilea peperomioides may re-grow leaves near the top of the stem (but not all along the stem). Give it ideal growing conditions and you should see new leaves when the growing season begins if roots have not been damaged.
Chalky, white circles on the underside of leaves is not unusual. It is mineral residue that comes from your water supply and from the soil. The bottom of the leaf is where the stomata are located, microscopic cells that allow gas to enter the leaf for photosynthesis and through which water vapor escapes. Tap water that you use to water the plant may leave the minerals behind as it escapes as vapor. If you look very closely you can possibly also see a white bump inside some of the circles where the minerals have crystalized. It is nothing to worry about. It is a good idea to wipe the leaf occasionally with a cloth dipped in warm water to remove the buildup, clean off dust and prevent the stomata from getting plugged.
Leaf cupping is natural when the leaf first opens. Leaves should flatten out and cupping of mature leaves is a sign of distress most associated with too little light, but can also indicate that some other plant care requirement needs adjustment. Review the plants routine above and make changes as necessary.
Long, drooping stems on a young plant indicates low levels of light. But it is also the natural growth habit of pileas to gradually become more bare at the base as they shed older leaves and for the plant to droop, losing its compact habit as it ages. Some people find them too straggly to keep as houseplants when they age like this. If you rotate the plant regularly so that it has a balanced shape it can still be attractive, though different.
The Complete Houseplant Survival Manual by 
