Swede and Siberian Kale

Botanical name : Brassica napus

Synonyms : 

Common name : Siberian kale, Russian kale, Rutabaga, Swede, canola, rapeseed

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Growing for seed

Brassica napus varieties include some types of canola and rapeseed and will need to be isolated from those crops and any wild populations, as well as other typical garden varieties such as rutabagas and Russian kales. Isolation distances of at least 250 metres are required.

These garden crops also require vernalisation to initiate flowering. The number of cold hours needed varies considerably across the varieties. Many locations in southern Australia are ideal for vernalisation of Brassica napus crops to produce seed. Temperatures below 4 C but above -10 C are generally ideal. All that is required is enough hours at those temperatures to trigger the variety to flower.

Plants must be mature enough before vernalisation starts for flowering to be triggered. This usually means a minimum of 8 true leaves. Better seed will be produced by stronger, bigger plants so sowing in mid to late summer is usually required to achieve good sized plants before vernalisation starts. Flowering then begins after the required number of cold hours have occurred.

In Australia there are few locations that get cold enough to winter kill these Brassica crops. No special actions need to be taken to over-winter Brassica napus crops unless extended periods below -10 C are expected. They can be left in the ground to grow through winter. They will then flower in their second growing season.

Note that in Australia winter occurs in the middle of the calendar year, but we have inherited the term “biennial” from the northern hemisphere. Where it means the “second year” as they change calendar years during their winter. In the Australian context our second growing season, after a period of cold, occurs in the same calendar year. It does not take two years to save Brassica napus seeds in Australia.

Selection

Plants being grown for seed should be selected on form and vigour. Specific traits will depend on the variety being grown for seed.

Harvest

Pods mature at the bottom of flower stalks first. The first set pods will be at risk of splitting and seed falling in the garden while possibly still flowering at the top of the stalk. The biggest and best seed will come from the first set pods. Cut flower stalks as soon as the bottom most pods are brown and crisp. If there is any sign of those pods starting to shatter in the field the stalks should be collected promptly.

Stalks can be put into large harvest bags or spread out on tarps for drying.

Processing

Dried stalk and pods are easily threshed by walking on them. Sieves can be used to remove the seeds from the bulky stalk and pod fragments. Winnowing will remove smaller frass and leave the seeds.

Storage

After processing seed should be left in a paper bag for a few weeks. Even these small seeds can hold a surprising amount of moisture.

There is a fair likelihood that insect pests will have laid their eggs in or on the seed. To stop them in their tracks one of the easiest methods of control is to freeze the seed for a few days. To do this the seed must be absolutely dry first. It then must be placed in a sealed airtight container – like a glass jar – and left in a freezer for 48 to 72 hours to kill pests and their eggs.

Seed is best stored in an airtight container where it is dark, cool and dry.

Contributors

Liz Worth, Nellie Pryke