One of the country’s biggest, and most colorful harvest festival every May 15th, along with the harvest festivals of the towns of Tayabas, Sariaya, Gumaca and Tiaong. These are the Philippines best known harvest festivals to honor San Isidro Labrador, the patron saint of farmers. Known as the “Pahiyas”, the festival is deeply rooted in the traditional celebration of the townsfolk in thanksgiving for bounty harvest. Decorations called “Kiping”, leaf-shaped and multi-colored rice paste wafers which are used to decorate the facades of the homes along with fruits and flowers from nature. The visual and culinary feast has gained national and international recognition.
The Lucban town center is a permanent facility for merchandising crafts and delicacies including special events that showcases the lifestyle of its environs.

History
The festival's name comes from the Filipino terms hiyas (jewel) and pahiyas (precious offering). This feast is an ancient farmers' harvest celebration that dates back to the 16th century. According to legend, San Isidro Labrador magically plowed the field whenever he went out of the church. This is the story that the Spaniards passed on to the Philippines from Mexico during their colonial period. Since then, the Pahiyas Festival has been a source of excitement for the locals and visitors of Quezon Province.

Customs
The highlight of the festival is a procession along the streets of the image of San Isidro Labrador, to ensure the people's bountiful harvest in the coming seasons. The procession features a pair of giant papier mâché figures of a farmer and his wife. This is followed by the image of the patron saint and his wife Sta. Maria de la Cabeza, who carries a basket with triangulo biscuits, which are given to the children during the procession. This culminates with generous sharing of food among the townspeople.
All the locals' houses are decorated with agricultural harvest (fruits, vegetables, rice grains, rice stalks, flowers, and ferns) and colorful rice wafers, called kiping. These thin wafers made from rice dough are usually arranged into two or three layers of chandeliers called aranya. The locals use different kinds of leaves to add flavor and color to the kiping. They also produce varieties of tastes and textures by using different ingredients such as kabal, coffee, talisay (umbrella tree), cocoa, and banaba leaves.
Each house tries to outdo each other in decorations in an annual competition as they vie for the honor of being recognized for their creativity. After the competition is over and the awards are handed over to the owners of the winning house, the decorations of the house will be thrown away to the huge flock of people as free treats. For the other houses, after the festival, those kipings that were used as decorations are cooked and eaten as rice chips. Also during the festival, the people display their harvest in front of their homes so that the parish priest can bless them as the procession passes by.

Sources:

http://www.tourism.gov.ph/sitepages/FestivitiesList.aspx?festivityCode=303&monthCode=05

http://www.pahiyasfestival.com/home/

http://www.ourawesomeplanet.com/awesome/2012/05/pahiyas-festival-dont-miss-the-fun-in-lucban.html