MSU Extension Vegetables

The plant family Brassicaceae is also called Cruciferae because their four petalled, yellow flowers resemble a crucifix. Edible members are often referred to as cole crops and contain several of our better-known vegetables such as turnip, kale, cabbage, broccoli, cauliflower and others (see table below). The physical appearance of these crops vary greatly, as does the plant part we eat. We eat the root in radishes, turnips and rutabaga; the leaves in kale, collards, arugula and cabbage; the swollen stem in kohlrabi; and immature flowers with broccoli and cauliflower.

We also raise canola seed for cooking oil, and one member (Arabidopsis thaliana) has been helpful in understanding the working of genetic systems. Some members of the family are annuals (planted every year), others are biennials (planted one year and flower and fruit the next) and some are perennials. I cannot fail to mention some are problematic weeds. However, most are edible to some degree.

Cole crops have been food crops for thousands of years, and prior to modern transportation and storage techniques they were easily stored for winter consumption as a plant part or as a fermented product (sauerkraut), and in northern climates provided necessary vitamins and other vital nutrients when fresh vegetables were not available. It is easy to see that without this plant group, our diets and scientific understanding would be much different.

The Brassica genus appears to be in a state of flux. What I mean is that as a group they still seem to be sorting out their identity as individual species. Some members vastly different in appearance but readily intercross and produce viable seed through standard breeding techniques, indicating they are similar genetically. However, other members do not easily cross but can be crossed to another “bridge” member that assists in transferring genetic traits, indicating a genetic distance great enough that they cannot be directly interbred but close enough that another member can be a go between. Then there is the case of Brussels sprouts, which is of recent origin with the first references occurring in the late 1500s. All this indicates a great ability to change and develop new types, which we have seen in recent years.

As diverse as the genus is, they all have a common center of origin, the Mediterranean region. Originating from that area gives an indication of the growing conditions in which they do best. A Mediterranean climate has warm (not hot), dry summers and cool (not cold), wet winters. They most prefer the cool. They primarily like growing temperatures between 55 and 75 degrees Fahrenheit. Many are frost-tolerant and will withstand temperatures in the mid-20s, but will freeze when conditions reach the lower twenties. Temperatures above 75 F will slow growth and cause other potential quality issues such as bolting (going to flower), loose head leaves or sprout leaves, and stronger flavor.

These temperature restrictions indicate that in a Michigan climate, they should be spring planted as early as possible with harvest by late June, or planted late-July with harvest in September and October. Time plantings so they do not mature during the heat of July and August. They respond well to plasticulture systems and summer plantings can actually take advantage of the inputs of an early-planted summer squash or slicing cucumber planting after they have been removed in July. After harvest, they should be quickly cooled using forced air or ice and should not be stored or shipped with any ethylene generating fruits.

So, what is the “diva” thing I mentioned in the title? As outlined above, cole crops have stringent climatic demands for producing high quality products. However, the prince/princess/prima donna or the diva, if you will, amongst cole crops is cauliflower. It takes a great deal of pampering to get high quality cauliflower. Growing conditions have to be just right—not too hot. They cannot be treated too well with water or fertilizer or they “rice” (see first photo), but not enough and you will get poor yields. The rice effect does not refer to the popular culinary procedure, but rather to the small protrusions that give the “curd” a fuzzy appearance. They do not change flavor, only appearance. However, we have the problem that before food goes into our mouth it has to get past our eyes. Therefore, if it does not look as expected, we do not want it. They also need to have their leaves tied up around the top of the developing curd so it remains white. If not tied, the curd will take on a yellow-tan color that is, again, undesirable to the consumer.

Mark Twain once said, "Training is everything. The peach was once a bitter almond; cauliflower is nothing but cabbage with a college education." He did not say this to belittle cauliflower, but to indicate the extreme effort in his day that went into cultivating cauliflower compared to cabbage. It is a bit easier to cultivate today, but it still very much remains a vegetable diva.

Adapted from: Maynard and Hochmuth, 1997 and Larkcom, 1991.