Most large greenhouse have automated packing lines, similar to those used for packing the field crop, except that greenhouse tomatoes are usually packed in stackable single-layer boxes. Greenhouse tomatoes are generally not stored for more than the few days necessary to move the crop to market but it is important that even in this short periods that temperature and humidity conditions are optimal: 10-13°C and 90-95% relative humidity. Because tomatoes are picked at the breaker stage or later, artificial ripening with ethylene is unnecessary. In fact, tomatoes are a source of ethylene, and should not be stored with ethylene-sensitive crops such as pepper, lettuce, and cucumber.