Tulip. Macrophotograph of a tulip flower Tulipa sp. showing its stamens and carpel. The shorter stamens (male reproductive parts) consist of a pollen- bearing anther (yellow) on the end of a stalk-like filament. The taller central carpel is fertilized by pollen which lands on its tip (stigma) and travels down its style (green). Tulips are popular garden plants which flower in April and May.