I did a Google search and found these messages in another forum. Hope it helps,
K

I grow them here in Central Illinois, in zone 5b, but I do grow them in a pot. I take the pot outdoors when all danger of frost has passed, and I bring them in before the weather gets chilly, in late summer. Most of the time, I grow them as a houseplant.
The bulbs I have right now are young, so haven't bloomed yet... but I expect them to flower this year. I treat them very similar to most of my other amaryllids. It's possible to grow tender bulbs in northern gardens, as long you bring them in before the weather gets cold.
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I grow them here in the ground with no trouble. I live right on the line of zone5/6. They are on the south side of my deck in some shade. They multiply fast so I dig some and move them every other year. I know one other lady who grows them here and they are in the sun. Dig and move when the foliage disappears. I never dig and bring them in in the fall. They don't like to be disturbed, somewhat like the naked ladies.

Gramadea,

You should let your L.radiata bulbs get as much sun as possible at this time to ensure they bloom for you next season. A bulb with a circumference 4.5" to 5" should be of flowering size. They bloom ~start of fall, followed by the foliage ~2-3wks after bloom(the foliage will stay thru winter and die back spring-summer as the bulb goes dormant.) They can stand a freeze here in 8bTexas(naturalized here.) You may want to bring potted bulbs in during hard freeze but bring back out. In dormancy just leave in pot. Here they bake in ground while in dormancy(summer) >100degrees with occasional rains and they survive/thrive.