You can leave your lawn a few inches tall all winter and it won't mind at all. Do not mow when the ground is frozen of the soil very wet. If you do wait until spring to mow be sure to take just a bit off the top and gradually shorten the blades so that you are removing the top third and cutting into leaf blades rather than stems. Don't worry if you ignore all this and just scalp the lawn with a severe crew cut in the spring. It will take a few weeks but a healthy lawn will recover from mowing mistakes. Keep growing - and planting great plants for the birds - Marianne Binetti