The roots of the winter grass weed are very fine and it can find a home in any spare bit of soil or crack in the paving and if left alone will take over your lawn or garden.
You will need to get rid of the weed before it goes to seed as the little seed will sit on the ground ready to germinate and then reproduce very quickly. Spray the winter grass in the early part of the winter or as soon as you see it.
If you have winter grass in your lawn you will need a specialist weed killer as it is very hard to kill. The poison that you use does not react with the leaves of the plant, but in the root system, so after you spray your lawn give your lawn a light water to get the poison down onto the roots. Spray it again in about a week to make sure they are dead.