Lots of knitters walk away from yarns that are constructed from natural vegetable fibers and other inelastic fibers, because it’s harder to get an even look to the knitting.  This is such a shame, because these yarns are lovely to look at and wear.  One problem that most of us have is that our knit stitches and purl stitches are not exactly the same size (gauge), and this is true whether you throw (English) or pick (Continental).  For a quick fix you can 1) convert to knitting in the round, or if that isn’t practical, 2) try using a different size needle for the knit side and purl side. Also, don’t put down the work in the middle of the row, and if you are creating cables, use a cable or dp needle at least 2 sizes smaller to avoid stretching those stitches out of shape.  Finally it is most important to knit, launder and block your gauge swatch using the same methods you intend to use on the garment.