Rich and Strange Aeons

I have no idea about the weather, but most plants (there are IIRC some exceptions) have evolved for regular day night cycles, with the day being used to absorb solar energy and the night being used to process it (I don't remember the details). Also, I think plants need a day night cycle to flower.

In short, while I can't remember the details and google isn't turning up anything with more details (although it is confirming my memories). I think you'd have plants growing twice as fast for a while and then dying w/o reproducing, so doing this would be an impressive way to create mass famine in a few months.