Agapanthus problem

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I bought some Agaanthus bulbs in Madeira about three years ago and last year they flowered beatifully with loads of blooms. I reckon it took a long time to flower as I think they like to be potbound. However, this year it seems I only have one single bud. Has anyone any idea as to why? It is kept in a very sheltered spot outside and the pot is lined with bubble wrap, but we did have a short spell of VERY cold weather in the winter. I am hoping there may be some more buds perhaps later in the summer, but not too positive. Would appreciate some comments.