Answer: Nerine usually bloom in August-September-October. You didn't say whether you have them in the ground or in pots, but I'm going to assume pots as they are usually not hardy in your winters. Also, the bulbs don't like to be moved or disturbed, so rather than planting and digging in the fall, it might be better to grow them in pots.
Bulbs should be planted in spring in a sunny site. They like a well-drained soil with plenty of organic matter. They are usually dormant during the summer and do better if kept somewhat dry. They do need warm summer temperatures during their dormancy to flower at their best.
Bulbs should be planted about 3 inches deep, with about 1/3 of the bulb showing above ground. Water and fertilize only when leaves are actively growing, usually winter and spring. Reduce watering when leaves start yellowing, which means dormancy is approaching. For Nerine bowdenii, gradually dry off in early summer and let it go completely dry from summer until it blooms
If you have not already done so, try using a fertilizer that is only phosphorous, such as bone meal, or 0-45-0. Phosphorous promotes bloom over foliage. If overly fertilized with nitrogen, nerine has a tendency to produce lots of strappy leaves. I hope this info helps!
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