According to BBC.co.uk: Regardless, Van Gogh's paintings of sunflowers have altered mankind's perspective of art and life. He hung the first two in the room of his friend, the painter Paul Gauguin, who came to live with him for a while in the Yellow House.

The Van Gogh Museum will be using a total of 125,000 sunflowers to build a sunflower labyrinth on the Museumplein to celebrate the festive opening of the new entrance hall. He painted sunflowers as no one before him had ever done. The painter of Sunflowers.
This series consists of sunflower clippings verses sunflowers in vases. Some of Vincent van Gogh's most famous works are his Sunflower series. Vincent didn't always paint in the bright he's now so famous for. The sunflower paintings had a special significance for Van Gogh: they communicated ‘gratitude’, he wrote.

He painted a total of twelve of these canvases, although the most commonly referred to are the seven he painted while in Arles in 1888 - 1889. So, how did he come to create his masterpiece? Gauguin was impressed by the sunflowers, which he thought were ‘completely Vincent’. Nowadays Vincent van Gogh is known as the man who painted Sunflowers. Van Gogh did create some sunflower paintings prior to this time though in Paris, France around the time of 1887. One-hundred twenty-five thousand sunflowers will appear in Amsterdam’s Museumplein this weekend, marking the completion of the Van Gogh Museum’s brand new all-glass entrance. The largest labyrinth measures 7,000 m2 and covers almost half of the Museumplein. The sunflowers were perhaps also intended to be a symbol of friendship and a celebration of the beauty and vitality of nature.
The other five he had painted previously while in Paris in 1887. The sunflower pictures were among the first paintings Van Gogh produced in Arles that show his signature expressive style.