Heirloom plants are specific cultivars which are open pollinated, grown in earlier times of our history, and not used in large scale agriculture. There is no specific age that identifies an heirloom plant, but one widely accepted theory is that any cultivar over 150 years old fits the bill. However, there are some heirloom plants that only originated around the turn of the century. This leads to the theory that cultivars aged before the early 1950s, when hybridization became popular, are heirlooms.
There are many different theories about heirlooms, but only one real definition. Heirloom plants are open pollinated cultivars grown in an earlier era, and are not grown commercially. Open pollinated means the plants are pollinated naturally by birds, insects, and the wind. They do not require controlled or manual pollination, as do many hybrid cultivars. Open pollinated plants produce new generations of the same type, but genetic traits will vary widely among them.
Heirloom plants are different from the mass produced food crops grown around most of the world, and not only because they are open pollinated. For the sake of consistency, large scale agricultural businesses grow only a few varieties of each crop, chosen for their durability, tolerance to adverse conditions such as drought and pesticides, and productivity. Heirloom plants often provide superior color, flavor, nutrition, and variety.
Heirloom plants are highly adaptable, and in many cases have adapted to their native climate and soil. They are usually resistant to most pests and diseases, which is another part of their appeal. Heirlooms are particularly useful for organic gardeners, as they can collect seeds each season and grow more of the same crop the next year, without worrying that the seeds have been treated with pesticides.
There are thousands of different types of heirloom plants, from flowers to vegetables, and gardeners around the world appreciate them for their uniqueness. In many cases, heirloom seeds are passed down amongst family members to be enjoyed by later generations. There are some seed companies that specialize in heirloom seeds, giving gardeners the chance to experiment with many different cultivars. Heirloom tomato plants are some of the most popular in the United States. In South and Southeast Asia, heirloom plants of all types are widely grown.
Today, the interest in heirloom plants is growing rapidly as people look for more natural, local methods of producing food. In the United States, the Amish, Mennonites, and many Native American groups have been dedicated to the preservation of heirloom seeds. University ecology departments around the globe are also taking a special interest in heirloom plant preservation.