Answer: During the winter agapanthus appreciate cooler temperatures at night say 50 to 55 degrees and days of perhaps 65
degrees. If your temperatures are colder than that on a regular basis it's probably best to bring it indoors. In winter when growth is slow they should not be fertilized but watered lightly -- just enough to keep the soil from going dry. Next spring begin fertilizing again. Try a fertilizer higher in phosphorous which promotes bloom. I've included basic info on fertilizers below. Good luck!
Here?s some basic info on fertilizer and nutrients that plants require. The 3 numbers on a fertilizer bag refer to the percentage of N (nitrogen), P (phosphorous), and K (potassium) in the bag. There are different formulations for different purposes. In general terms, nitrogen produces lush green growth, phosphorous helps strengthen stems and produce flowers, and potassium keeps the root system healthy. If you're applying fertilizer to fruiting (e.g., tomatoes) or flowering plants, you're not as interested in the plant developing leaves as you are in it flowers and fruit, so you'd use a formulation lower in nitrogen and higher in phosphorous, such as Miracle-Gro's Plant Food at 15-30-15. Bone meal is an organic source of phosphorous.
Q&A Library Searching Tips