In the past, planting season for many horticultural crops began in May to avoid the threat of frost; however, traditional planting times may change for some commercial growers as more producers use high tunnels to extend the growing season. High tunnels have become a popular and profitable method to produce high-value crops. They are simple, tall, plastic-covered structures used for the production of fruits and vegetables, cut flowers, and many other crops. They resemble greenhouses but cost less to erect and operate.