You can buy a tip that will pipe grass. It has several small holes in it. It is very simple. You just squeeze and pull up. Be sure your icing is more of a medium to stiff consistency though or it will droop. :)
Thanks guys...will go in search of the tip...hopefully i find it...the individual piping sounds like pain..whooo...one had better be at my supplier..:).
It is very easy to use. That is what I used for the sides of my beach cake, as well as the roof of the tiki hut. Squeeze and pull up (or out on the side) - not down, like you would think. And, unless you want it to look more like a grass skirt (like the sides of my cake) keep it pretty short - small, quick bursts of icing, instead of squeezing and pulling out at the same time.... hope this helps!
Just a small aside - the same tip works great for adding details to daisy middles by using them to make an impression on the fondant. :)
I love making grass using that tip! Another trick I learned is to have 2 bags with the same frosting and tip because it takes a while to do a large area and if you find your frosting is getting too warm from the heat of your hands you can put it in the fridge and pick up the other bag and then switch them out as needed.