An heirloom is generally considered to be a variety that has been passed down, through several generations of a family because of it's valued characteristics. Since 'heirloom' varieties have become popular in the past few years there have been liberties taken with the use of this term for commercial purposes. At TomatoFest Garden Seeds we chose to adopt the definition used by tomato experts, Craig LeHoullier and Carolyn Male, who have classified down heirlooms into four categories:
Commercial Heirlooms: Open-pollinated varieties introduced before 1940, or tomato varieties more than 50 years in circulation.
Family Heirlooms: Seeds that have been passed down for several generations through a family.
Created Heirlooms: Crossing two known parents (either two heirlooms or an heirloom and a hybrid) and dehybridizing the resulting seeds for how ever many years/generations it takes to eliminate the undesirable characteristics and stabilize the desired characteristics, perhaps as many as 8 years or more.
Mystery Heirlooms: Varieties that are a product of natural cross-pollination of other heirloom varieties.
(Note: All heirloom varieties are open-pollinated but not all open-pollinated varieties are heirloom varieties.)
Where did the term "Heirloom" plants begin?
The term "Heirloom" applied to plants was apparently first used by Kent Whealy of Seed Savers Exchange, who first used "heirloom" in relation to plants in a speech he gave in Tucson in 1981. He had asked permission to use the term "heirloom" from John Withee, who had used the term on the cover of his bean catalog. John said sure, that he had taken it from Prof. William Hepler at the University of New Hampshire, who first used the term "heirloom" to describe some beans that friends had given him back in the 1940s.
The Importance of "Heirloom" Tomatoes.
In the past 40 years, we've lost many of our heirloom varieties, along with the many smaller family farms that supported heirlooms. The multitude of heirlooms that had adapted to survive well for hundreds of years were lost or replaced by fewer hybrid tomatoes, bred for their commercially attractive characteristics.
In the process we have also lost much of the ownership of foods typically grown by family gardeners and small farms, and we are loosing the genetic diversity at an accelerating and alarming rate.
Every heirloom variety is genetically unique and inherent in this uniqueness is an evolved resistance to pests and diseases and an adaptation to specific growing conditions and climates. With the reduction in genetic diversity, food production is drastically at risk from plant epidemics and infestation by pests. Call this genetic erosion.
The late Jack Harlan, world-renowned plant collector who wrote the classic Crops and Man while Professor of Plant Genetics at University of Illinois at Urbana, wrote, "These resources stand between us and catastrophic starvation on a scale we cannot imagine. In a very real sense, the future of the human race rides on these materials. The line between abundance and disaster is becoming thinner and thinner, and the public is unaware and unconcerned. Must we wait for disaster to be real before we are heard? Will people listen only after it is too late."
It is up to us as gardeners and responsible stewards of the earth to assure that we sustain the diversity afforded us through heirloom varieties.
Information source>> http://www.tomatofest.com/what-is-heirloom-tomato.html