What is turnip rapeseed?

Turnip rapeseed is often called "Polish canola" in North America and the Latin name is Brassica rapa.

 

The most common question about turnip rapeseed is probably not "What is turnip rapeseed?" but rather "What is the difference between rapeseed and turnip rapeseed?" or "What is the difference between Argentine and Polish canola?". Many people know that turnip rapeseed is an oilcrop with yellow flowers, just like rapeseed.

You could say that turnip rapeseed is a parent of rapeseed. If you cross turnip rapeseed with cabbage, you get rapeseed. Cabbage has 18 chromosomes and turnip rapeseed has 20. Rapeseed has all chromosomes from both parents and has 38 chromosomes. The relationship between some Brassica species is illustrated by the Triangle of U.

Triangle of U.png

Triangle of U shows that rapeseed is a cross between turnip rapeseed and cabbage.

Turnip rapeseed is earlier and grows faster than rapeseed. It means it flowers and matures earlier. Since time to collect energy is shorter it yields less than rapeseed. But in northern areas with short season the early maturity is needed to be able to harvest before winter.

There is both spring turnip rapeseed that is sown in spring and harvested in autumn, and winter turnip rapeseed that is sown in autumn and harvested in summer next year. Both grow fast and compete well with weeds. It is easier to grow turnip rapeseed than rapeseed without herbicides.

The fast growth is also an important trait to avoid insect attack. Winter turnip rapeseed flowers early in spring, often before harmful insects are active and is less dependent on insecticides for protection.

In autumn, the newly sown winter turnip rapeseed grows faster than rapeseed and can be sown 1-2 weeks later and still have time to grow large enough to survive winter. It may be hard to harvest previous crop early enough to be able to sow rapeseed, but with turnip rapeseed there is plenty of time. You can choose a later and more high yielding winter wheat as previous crop and still have time to sow winter turnip rapeseed afterwards.

The growth habit of winter turnip rapeseed means the winter hardiness is better than for winter rapeseed. The growing point is low and is better protected against cold wind that dehydrate the plant. Winter turnip rapeseed can stand winter without snow cover better and even a thin snow cover will protect growing point. Growth regulators are sometimes used in winter rapeseed to make plants shorter, but that is not needed in winter turnip rapeseed.

Another advantage with both winter and spring turnip rapeseed is the good shatter resistance. Turnip rapeseed can be left standing until it is fully ripe and will then give higher oil content and lower chlorophyll content.

To summarize, turnip rapeseed is a more robust crop than rapeseed. While rapeseed yields more at good conditions, turnip rapeseed often give better result at harsh conditions or short season. Turnip rapeseed is less dependent on agrochemicals. For organic farmers and for others who want to decrease use of agrochemicals, Winter turnip rapeseed is the best alternative.

Turnip rapeseed has smaller seed size than rapeseed with a thousand-grain weight of around 3 grams. Seeds can be black, brown, yellow or a mixture.