|6" x 6" oil on stretched canvas|
The trick to drawing something this complicated is to grid it into sections (in this case, two lines on each horizontal and vertical aspect will create 9 squares. You can print out a black and white copy and use a ruler to divide your subject into equal boxes or purchase an app such as ValueViewer so that you can do it directly on your device. You can scale up or down but it is easiest to keep the image you are working from the same size as the one you are creating.
With flowers, you can also just wing it and try to suggest and capture the essence of the flower without slavishly copying every petal.