Flowers drawings can look very effective when simply and cleanly drawn. For this example I chose a tea rose with a partly open bloom that seemed to lend itself to line drawing. The dip pen, which allows variation in line which adds interest and elegance to the drawing: drafting pens can look rather mechanical. A slightly textured or toned paper can also look good. If you aren't confident with pen, try drawing a very light sketch in pencil first, then doing the ink line. You may choose to use a very even, regular line weight for a crisp, illustrative look. Alternatively vary the weight, lifting the pen for a lighter line where the petal curves away from you.
More Flowers in Ink:
Draw a Rose in Fiber Tip Pen
Draw a White Lotus in 'Digital Ink'