The granny stripe takes the familiar clusters of the granny square and works them in straight rows. It is relaxing to make, reversible, and very forgiving.
The structure
Each cluster is three tall stitches worked into the same space: 3 tr in UK terms, or 3 dc in US terms. Clusters sit side by side with no chain between them.
On the next row, each new cluster is worked into the gap between two clusters of the row below. That offset gives the characteristic stepped, textured pattern.
Why it suits colour
Granny stripes are made for colour. Changing colour every one or two rows gives bold bands; using a long gradient yarn gives a soft, painterly shift.
Things to watch
Keep the edges straight by starting and ending each row the same way, usually with a half cluster at each side. Loose edges are the most common reason a granny stripe piece turns out wavy.