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| Chicorium intybus: Biennial or Perennial? |
Answered by: Conrad Richter
Question from: James Grattan
Posted on: June 19, 2000
Why does the Rodale Book of Herbs list Chicorium intybus as a perennial hardy to Zone 3? Your site lists it as a biennial. Which is it?
The duration and hardiness of plants is frequently a matter of some controversy. For many species the hardiness zones especially are rough guidelines at best, and completely misleading at their worse. The trouble with the best known system of hardiness zones, the USDA’s zones system (which the Richters catalogue uses), is that the USDA zones are drawn based solely on the average minimum winter temperatures. But hardiness is not simply a function of minimum winter temperature: snow cover, mulching, drainage, winter rainfall, wind exposure, moderating influences such as large bodies of water, and more, all have a large impact on hardiness. In addition, the zone ratings for the most part are not derived scientifically from controlled trials, but instead seem to be an amalgam of personal observations by gardeners and growers. Certainly, there is a need for a more precise system of rating hardiness of herbs and other plants.
Duration is less controversal. For most plants, it is clear whether it is a natural annual, biennial or perennial. However, there are cases where a perennial may be treated differently in the garden or cases where a perennial may not survive a third year in some areas.
For example, bronze fennel is considered perennial, but this past winter (1999-2000) second year plants that bore seeds for us last year did not survive the winter. In their places are new seedlings from the seeds that fell in the area last fall. The key to understanding this is to know that some plants, once they have produced a good crop of seeds, seem to be programmed to be weaker after seed set, and depending on the severity of the winter, may or may not persist into their third year.
In the case of chicory the duration is not affected by changes in the strength of the plant but by the increasing bitterness of the roots, the part of the plant that is used medicinally and as a coffee substitute. The literature suggests that chicory is indeed a perennial, but because roots over two years old are more bitter, the roots normally are lifted and dried in the second year. The plant, therefore, is treated as a biennial although it is really a hardy perennial.
It is a balancing act to decide these issues for the purposes of our catalogue. To a large extent we try to be as botanically correct as we can, but in the interests of giving our customers a realistic picture of the useful lifespan of a plant, we sometimes have to consider other factors besides merely the true duration of a plant.