Brassicas (especially Brassica rapa) are a crop that is probably impossible for the average home gardener to grow to seed successfully in a way that keeps the seed strong for the long haul.  Traditionally areas of Europe had their own wild populations of widely varying Kale, or cabbages and each area had only one variable cultivar. Sometimes they were more like kale, sometimes more like cabbage, etc. 

Each year the seed would be saved from the best ones but they remained widely variable and genetically strong. All parts of the plants would have been eaten, the leaves and stems and flower heads. Out of the genetic variability so many amazing cabbages and cauliflowers and broccolis and kales have been bred and selected over the last few hundred years but to keep these lines strong and the same the process is very difficult.

Koanga Institute is running an appeal to gain the support we need on an annual basis to keep enough brassica lines alive for the long haul for our northern conditions (click here for details of our “Adopt a Cabbage” scheme). The only Northland Heirloom brassica in the rapa species we have in our collection is Dalmation cabbage and that will probably be the easiest and the most nutritious one to keep alive if you’re keen to grow your own seed.

Seed Saving Information

Brassicas are insect pollinated and cross within species only (see following chart) so if you want top try growing your own seed you must plant a minimum of 300 plants, rouge out the100 least true to type, and save the seed from the rest. Seed to Seed says you must have I mile between flowering cultivars of the same species but I’ve found the distance can be far less depending on hills and valleys and what is in between.

Cultivation

There is quite an art to growing great brassicas. Here are some tips from us:

Sow brassicas during the months of January, February, March (April/May in warm areas) and then August and September. This avoids loads of pest problems (like white butterflies) trying to grow vegetables in a warm climate they are unsuited to. Colder areas plant in Sept, Oct, Nov, Dec, Jan, and Feb. If you have a white butterfly problem I suggest you put a Cloche hoops over the bed and cover with microclima cloth (available in our shop) until it’s too cold for butterflies.

Sow a wide range of varieties so they ripen over a long period, 3-5 months for most cabbage cauli and broccoli. Collards and kale will extend that season, as will sprouting broccoli, as well filling in gaps during that time.

Sow small amounts of seed in rows across your 3cm deep trays, and prick out as soon as they have second pair of leaves at 5cm centres into 7cm deep trays.

As soon as the leaves are touching they can be transplanted into the garden.

The garden soil they are being planted into must be free draining as they are a winter / early spring crop and will be adversely affected by water logged roots.

If you don’t have garden beds with high nutrient levels the plants will need to be liquid fed before and after full moon with comfrey, fish, liquid cow manure etc.

Brassicas love lime as well as lots of nutrients. We always compost and dolomite our brassica beds before planting, and then liquid feed with cow manure tea.