Knitting yarns also come in "variegated" colors, which change every few inches. You can get multiple colors from one skein.
The colors of acrylic yarns are pretty fade-resistant. The yarn won't decompose. You'll have to collect any that fall to the ground to keep from having multicolored soil or mulch. One way to prevent this - instead of tying the yarn around just the base of the flower, also tie it around the stem the flower is attached to, in a figure-8 if there's room to maneuver.
Pat
