Here's a pic of my brussel sprouts with a beatuiful layer of frost (2006/2007). 
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<img src="http://www.january31.com/photo-blog/LateFall2006/154211594885_th.jpg">
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Brassicas, of course, LOVE the cold! I was picking a few tiny ones from those plants this Spring: 

<img src="http://www.january31.com/photo-blog/Spring2007/169713298565_th.jpg">