Problem: Weak, leggy plants
Cause: Lack of sunlight
Solution: Find a sunny spot by a window, away from forced air vents. Pinch back to two healthy leaves to increase fullness.
Problem: Lack of good natural sunlight
Cause: Window faces north or east
Solution: Supplement natural light with a fluorescent grow light.
Problem: Spindly, leggy stems
Cause: Low winter light levels
Solution: In mid-winter decrease the heat slightly, and water less.
Problem: Leaf drop
Solution: Acclimatize your plants slowly by moving them into the shade for a few weeks before bringing them indoors.
Problem: One-sided growth
Cause: Light from one side only
Solution: Turn your pots ocasionally to encourage 360° growth.
Problem: Soft growth
Cause: Too much fertilizer
Solution: Avoid fertilizing during the winter as this encourages soft growth, which is more susceptible to pests and diseases.
Problem: Yellowing leaves
Cause: Possible overwatering
Solution: Dehydrating wind isn't a factor indoors, so water less than you would outdoors. The soil should be just moist-not too wet.
Problem: Failing plants
Solution: Maintain good airflow and don't crowd plants too closely together.
Problem: Spots on the stem or on the roots, plus wilting
Cause: Possible stem rot, crown rot or root rot
Solution: Check to make sure soil drainage is good, and reduce watering.
Problem: Evidence of pests, i.e., webs, etc.
Cause: Aphids, spider mites or white flies
Solution: Wash plants and pots with insecticidal soap before bringing them indoors.
Problem: Brown, wilted leaves
Cause: Dehydration, overwatering (the symptoms are the same)
Solution: Buy an inexpensive water meter at a garden centre to be sure. In the average Canadian house in winter, when light levels are low and you aren't feeding plants, their growth is almost stopped; watering once a week should be quite sufficient for most types of plants.