Lisse, Netherlands, takes on the appearance of a patchwork quilt in the spring. The best time to see the tulips is April and early May. (EPA/Remko de Waal)

Every spring, tulip farms in the Netherlands paint the landscape with bold colors. The country is known for its flowers. Two-thirds of the world’s cut flowers were grown in the Netherlands in 2005, worth $4.2 billion, according to the U.S. Department of Agriculture.

Red, pink, yellow and purple are favorites among the Dutch and their tourists.

The area around Lisse is covered in fields of tulips. They’re grown primarily for bulbs, but some gardens are of the pick-your-own variety. Keukenhof is probably the most popular tulip garden in the Netherlands, where 7 million tulip bulbs are planted each year, according to the office of tourism. The best time to see the tulips is in April and the beginning of May.

The tulip craze has spread across the world, too. Turkey, India and China all boast similar festivals at pick-your-own farms. Like its neighbor to the west, Germany cultivates tulips for the bulbs. At Degenhardt-Sellmann Spezialkulturen in Schwaneberg, Germany, about 100 acres of tulips are grown.

In Oregon, the Wooden Shoe Tulip Farm hosts an annual tulip festival from late March through April. More than 10 varieties of tulips are grown there.

Last year, a Dutch couple brought the Netherlands to Italy when they opened a pick-your-own tulip farm outside Milan. The farm, created by Edwin Koeman and his girlfriend Nitsuje Wolanios, covers about 2.5 acres, with 183 varieties of tulips, the Associated Press reported. The tulip season in Italy is only two to three weeks.

Despite the obvious beauty, large-scale flower cultivation has a downside, especially in the Netherlands — fertilizer runoff that infiltrates the ground water and oceans. A recent European Union directive attempted to limit the amount of nitrates used in agriculture, and although the amount of fertilizer decreased in the surrounding waters, the Netherlands was unable to meet its goal.

An aerial view showing farmers, seen as small dots, in a yellow patch in tulip fields. (AP Photo/Peter Dejong)

A man removes tulips with a different color in a field near Lisse, west central Netherlands, on April 17, 2018.  (AP Photo/Peter Dejong)

Fields of blossoming tulips are shown in Den Helder, northern Netherlands, in 2016. (AP Photo/Muhammed Muheisen)

Indonesian children run through fields of blossoming tulips as they have their picture taken near Noordwijk, western Netherlands, in 2012. (AP Photo/Peter Dejong)

A tulip field is pictured at the Keukenhof park, also known as the Garden of Europe, in 2014. Keukenhof, employing some 30 gardeners, is considered to be the world’s largest flower garden displaying millions of flowers every year. (REUTERS/Yves Herman)

An aerial view on tulip fields of the Keukenhof in full bloom (EPA/Jerry Lampen)

A classic car taking part in a rally passes fields of blossoming tulips near Noordwijk in 2012. (AP Photo/Peter Dejong)