Iris flowers are complex, folded, curling masses of twisted petals and sepals. How do you approach drawing something with so many curling and overlapping layers? The secret is to lay out the structure and then use shapes and negative shapes. Close one eye and flatten the 3D image to interlocking 2D shapes. Click on the first image to start a step-by-step slide show.
Lay in the basic proportions (height, width, and central axis) with a non photo blue pencil. Block in the rough proportions of the large central sepal. Observe the width of contour of the negative shapes next to the central sepal. Do not color these in, they are only shown here to help you see the negative shape. Block in the outer sepals beyond the negative shape. The developing form without the negative shape. Block in the locations of the pistils. Note that there is no detail in these shapes, only proportions. Block in the position of the central petal (yes those narrow things on the top are the petals). Observe the width and contour of the negative shapes on either side of the central petal. Block in the outer petals on either side of the negative shapes. The developing form without the negative shapes. The non-photo blue pencil is very pale. You can draw over it without needing to erase if you go lightly. Now look at the shape of the central sepal. Do not think of it as a curling petal. It is an abstract shape, curved top, angled sides. Because you have the blue pencil layout, you can add shapes anywhere. I start with the flower parts that are closest to the viewer and then work my way toward the back. Whenever you look up at the iris, close the same eye. When you draw, keep both eyes open. Continue to add interlocking shapes. Next to shapes. Next to shapes. Continue from front to back. Iris pistils are petaloid, or petal shaped. They have two lobes at the tip. Iris flowers have parts in threes. Three sepals, three pistils, three petals. Build the petals the same way. Shapes next to shapes. Draw the rear petal more lightly, suggesting that it is further back. Add a little detail in the foreground. The curling lines on the sepals suggests a curved surface. Value also suggests the curls of the surface. Use shadows and highlights to suggest depth.