I had some bulbs planted under big leafed Canna Lilies which shaded the Amaryllis from April on. For 5 years, the Amaryllis wouldn't bloom and looked miserable. In desperation, I moved the Amaryllis to their own bed in full afternoon sum. It took 2 years for them to recover, but now they bloom. Other "spring" bulbs, such as tulips or daffodils can be interplanted with perennials, since they die back before the companion plants shade the foliage. Amaryllis foliage needs good sunlight all summer. So in cases of poor blooming, I always advise increasing the sunlight and getting them away from root competition for moisture.
