the way I understand it, even in the winter , on warmer days, the grass
can make sugar. In the summer time it is usually used up at night for
growth. In the winter or fall or spring, the night time temps can be
much colder, thereby stalling growth and the use of sugar. This means
that the sugars will remain in the grases and potentially even built up
more over time. That's why fall and spring grasses can be so dangerous,
along with supposedly "dead" grass in the winter!