Adding grass to a picture is something I really enjoy doing. It's instant play. Playing with textures and colours all at the same time.

Here on the picture are two labels that read what kind of wool they are. They are of course knitting wool, but more so they are pure wool and not an artificial wool. Remember, artificial wool has no scales to felt.

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The green one is 70% mohair wool and 30%silk. The pink one is 100% merino wool. This will felt no problem.

Be careful with wool that says super wash. The label will state that it is wool, but it's treated with a chemical and so it won't felt. I am also using wool that I know will not latch on to my underground wool layout. In that case, I cover the knitting wool ever so slightly with some merino batting. This will act like a web to secure the knitting wool when I felt it.. Later on when we have the project under the sewing machine we can also give it a stitch or two if need be.

Overall though, wool that will felt will give you some interesting structure into your picture to imitate grass. So keep an eye out. You never know where and when you come across it.

One bit of advise. Use more wool to imitate grass then you think you need. A lot goes lost in the felting process. Meaning it will sink into the background and is hardly visible. Add enough of it and don't be afraid. I always use lots and lots. Especially finer wool has a habit of disappearing.

Again Esty is a fantastic source for natural knitting wool.

Here is a link for such wool.