As the spear ages, lignin accumulates in the pericycle region to provide support for the ferns. The usual location for the initial buildup of lignin is the butt end or the white basal stem area. Traditional asparagus varieties are dioecious, meaning that they have male and female reproductive structures on different plants. Female plants produce spears and also produce seed when the plant is in the fern stage. The production of seed diverts photosynthetic energy from spear production and reduces the yield of spears.
Male plants yield more asparagus with no seeds produced while in the fern stage of growth.
New Jersey Male Hybrids Dr. Howard Ellison, asparagus breeder, and Dr. Stephen Garrison, Extension Specialist in Vegetables at Rutgers University in New Brunswick, New Jersey, have devoted their lives to asparagus breeding and cultural practice studies. Ellison observed that although asparagus produces both male and female plants, about one in 500 male plants will produce male flowers and a few flowers with functional male and female parts. These male hybrids have tolerance to asparagus rust and Fusarium crown rot, two major fungus diseases that affect asparagus. Some of the more popular New Jersey male hybrids include Jersey Giant, Jersey Knight, and Jersey Gem. First harvest in 1994.