Late-summer pickles take longer because cooler temperatures and shorter days slow the growth and development of the plant. Pickles are usually double-cropped with any one of several crops. Often pickles follow pickles. In the early 1960s, a breakthrough in cucumber breeding by USDA workers at the University of Wisconsin lead the way for the mechanical harvest of pickles. These scientists developed the first gynoecious lines and a technique for maintaining gynoecious lines for breeding and commercial seed production.
Gynoecious plants express female flowers for an all-female phenotype.
This allows the pickles to mature at the same time, which facilitates a single harvest. Male varieties are mixed with the seed of gynoecious varieties to provide a source of pollen. These innovations in plant breeding stimulated and encouraged the development of mechanical harvesters. Workers at Michigan State University developed the basic design and operating principles of the tractor-mounted harvesters, which are currently the predominant type of harvester in use. There are also recovery and quality issues that occur with the larger pickles.