From Gardening
Solutions
Institute of Food and Agricultural Sciences, University of Florida
Cole Crop Confusion
And the Genus Brassica
In
Florida, winter is cole crop season: cabbages, Brussels sprouts,
broccoli, and more! You may have also heard these plants referred to as
"cruciferous vegetables." They are also called "brassicas." Different
regions and professions use different names. Some are scientific but
most are informal titles for varying lists of crops. There is plenty of
confusion surrounding the cole crops.
Genus Brassica
Did
you know that kale, collards, kohlrabi, cabbage, Brussels sprouts,
broccoli, and cauliflower are all considered one species? It's true.
Scientists refer to them by a single scientific name: Brassica oleracea (B. oleracea). The
genus Brassica
is where we get the informal name, "brassicas."
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Fig. 1 Freshly harvested kale |
No matter which cole crop list you consult, most will be members of B. oleracea. Some
lists include other Brassica,
like turnips and mustards. Others include non-brassicas, like
watercress.
The UF/IFAS Vegetable Production Handbook of
Florida pdf chapter on cole crops lists twelve: broccoli, cabbage,
cauliflower,
Chinese broccoli, Chinese cabbage, Chinese mustard, kohlrabi, oriental
radish, collards, kale, mustard, and turnips. Another research
institution's list restricts itself to only four: broccoli, Brussels
sprouts, cabbage, and cauliflower. Because "cole crop" is an informal
term, lists vary wildly. This is where much of the cole crop confusion
originates.
This confusion is not limited to informal terms and
lists, either. Even botanical names (scientific names) are subject to
disagreement. Some scientists would add to the list of plants in B. oleracea.
Others would subtract or rearrange entirely based on genetics. As
classification begins to take recent findings in molecular biology into
account, disagreements grow. We can clear up some confusion by
exploring the concept of a species.
The Species
Concept
Most
botanists and plant scientists agree on the following definition of a
species: a group of living things that can interbreed and produce
healthy, fertile offspring. In other words, researchers consider two
plants one species if:
1. They can be cross-pollinated AND
2. Produce seeds AND
3. Those seeds can grow and reproduce as well
Kale,
collards, kohlrabi, cabbage, Brussels sprouts, broccoli, and
cauliflower all pass this test. As a result, they are a single species.
One Species, Many Varieties
Clearly,
the members of Brassica
oleracea exhibit different physical traits.
This is because Brassica
breeding has been going on for millennia.
Sanskrit texts from 2000-1500BC contain references to cultivation in
India. Greek texts date Mediterranean Brassica forming
back to the 6th
century BC.
Ancient farmers bred wild varieties to enlarge
different parts of the plant. Kale and collards are varieties with
larger, longer leaves. Broccoli and cauliflower are huge flowering
heads. Cabbage and Brussels sprouts are enlarged leaf or stem buds.
Finally, kohlrabi has been selected for its thickened stems.
Because
of the obvious differences in form and use, each member of B. oleracea
is also given a variety name (var). This helps to distinguish them for
horticultural purposes and for use in scientific literature. Below are
examples of some variety names in B.
oleracea.
Some B. oleracea
varieties and their common names
•
Brassica
oleracea var. botrytis
— cauliflower (broccoli)
•
Brassica
oleracea var. gemmifera
— Brussels sprouts
•
Brassica
oleracea var. gongylodes
— kohlrabi
•
Brassica
oleracea var. italica
— sprouting broccoli
Cole Crop
Confusion
If
the scientific names you remember differ from the ones above, don't
worry. You're not alone. The confusion over botanical nomenclature
(naming) is rampant in gardens and classrooms alike.
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| Fig.
2 Flowers of a member of the B.
rapa species. Small floppy yellow flowers gathered at the top of a slender green stem. |
Botanists
and horticulturists often prefer the most recent and scientifically
defined term, Brassica.
And while this name is a current taxonomic
genus, its members change often. Brassica
is a difficult group to
classify due to a long history of cultivation and hybridization. New
discoveries in genetics mean that the taxonomic system is being
rearranged frequently. Still, most horticulturists agree that the
following species belong in genus Brassica:
•
Brassica
oleracea — kale (collards), kohlrabi, cabbage, Brussels
sprouts, broccoli, and cauliflower
•
Brassica
rapa — turnip, pakchoi, Chinese cabbage, rutabaga, rape
(rapeseed, or canola)
•
Brassica
nigra — black mustard (condiment mustard)
•
Brassica
juncea — oriental mustard (yellow), Indian mustard (brown)
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Fig. 3 Shanghai bok choy in a California farmers' market. |
Many
older group names, such as "cole crops" and "crucifers", are informal
or historical. Regional groups and certain occupations tend to use
these out of tradition and convienience. Cole crop is a term used often
in agriculture. It usually describes plants cultivated using similar
methods. Cruciferous vegetable is a phrase that originally referred to
a taxonomic family, Cruciferae. Though considered synonyms, modern
texts often choose Brassicacea over Cruciferae. Thus, "cruciferous"
remains a popular term, especially in culinary texts and diet plans.
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Bibliography
"Cole Crop Confusion." Gardening
Solutions, UF/IFAS, gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/cole-crop-confusion.html.
Accessed 9 Dec. 2020.
Photographs
Fig. 1 Gardening
Solutions, UF/IFAS, gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/cole-crop-confusion.html.
Accessed 9 Dec. 2020.
Fig. 2 Lavin, Matt. "Brassica rapa.
The inflorescences and flowers are very similar among the different
species and varieties of Brassica (e.g., four large yellow petals
alternating with four sepals and six stamens, numbers distinctive to
the mustard family Brassicaceae)." Gardening
Solutions, Flickr, UF/IFAS, (CC BY-SA 2.0), gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/cole-crop-confusion.html.
Accessed 9 Dec. 2020.
Fig. 3 Cheung, Lance. "Shanghai bok
choy in a California farmers' market." Gardening
Solutions, USDA, UF/IFAS, gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/cole-crop-confusion.html.
Accessed 9 Dec. 2020.
Published 2 Apr. 2021 KJ
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