Fennel - Annual or Perennial in Zone 5?
Answered by: Conrad Richter
Question from: Linda Choquette
Posted on: February 7, 1999

I will be mailing my herb order shortly since I have been pouring over your wonderful catalogue for weeks now. I just noticed a bit of a conflict though: your catalogue says bronze fennel is a perennial, but your info sheets based on Ontario Ministry of Agriculture say fennel is an annual. I live in Ottawa which is zone 5. What do you think?

Yes, there is an inconsistency between the catalogue and the government’s info sheet. There are several reasons for that.

Fennel is at the limit of its hardiness range in southern Ontario. Formerly, it was commonly assumed that fennel would not be hardy in zone 5, but herb enthusiasts are getting it to winter over in the warmer parts of southern Ontario. I would not say that it is reliably hardy in zone 5, our zone in Goodwood, but it will come back some winters – enough to wait and see before digging out the roots in the spring. As you move toward moderated areas closest to Lake Ontario and south west toward Windsor, in areas closer to zone 6, fennel is more reliably hardy.

The hardiness question is complicated by the common confusion between the seed-bearing type of fennel (Foeniculum vulgare dulce) and the bulbous base-forming type, the florence fennel (F. vulgare azoricum). This latter type is a vegetable, and it is not winter hardy anywhere in Ontario, and so should be regarded as an annual.

Bronze fennel is of the non-bulbous type and is similar to the other sweet fennels in hardiness.

A final point: the hardiness rating system is not an exact science. There is an increasing reliance on the hardiness zone ratings of plants by both the plant industry and gardeners, with the potential of preventing gardeners from being more adventurous. In the case of fennel, it is quite easy to grow it as annual and get a harvest, even in zones colder than 5 or 6. We are concerned that gardeners and herb enthusiasts in zones such as 2, 3 and 4 are choosing not to try herbs such as fennel based only on the hardiness ratings. What we really need is a "feasibility" zone rating system in which the zones indicate which herbs can be grown outdoors successfully to yield a harvest. The "feasibility" zone ratings for sweet fennel would be something like 2-10, where from 2-4 it will be an annual, and from 5-10 it will be a perennial. On the other hand, a tropical plant such as neem would be rated "feasible" in zone 10 only, the same as its hardiness zone rating, because it is a tree that takes several years to reach harvestable size.

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