I plan on growing a few different brassicas such as cabbages and bok choy, and I'd like to collect seeds from these open pollinated varieties so that I don't have to keep buying seeds.

How do I prevent cross pollination occurring between different varieties so that they breed true?

3 Answers 3


I guess you can do it as for other varieties?


Cover the flower heads.

This technique (also known as "bagging") will need to be done before the flowers open so that bees and any other pollen transporting insects are preventing from getting to them.

For covering the flowers only, try such items as:

  • Toilet rolls
  • Muslin or similar sachets or bags (these can be tied in place)
  • Handkerchiefs
  • Plastic beverage or food containers (cleaned).

There is also a more complete explanation on how to do at http://howtosaveseeds.com/isolate.php

Hand pollinate

I think the surest way is Bagging and hand pollination... But it is much work.

If you just want to avoid buying seeds every year

If you only grow one variety to flowers, and your neighbors don't, then you can probably take the risk to grow one variety of seeds per year by just leaving the plants as they are. This assumes most of the seeds will give the same kind of plants, and some will have been pollinated from far, but only a few.

However I know you cannot do that too many times, and must buy new "commercial" seeds. Leave this hard "hand-made pollination" to small biological farms, and buying seeds to them will help them sustain.


Cover the plants with lightweight fabric or row covers, and hand pollinate them yourself. It's a lot of work, and keep in mind that brassicas are biennial so you'll have to wait until year 2 to get flowers and seeds. Also be forewarned that most of the brassicas are really large and ugly when they set seeds. I did this with kale one year and I won't do it again.


Pac choi is a different species from cabbage so they will not cross. Cabbage, some kales, cauliflowers, brussels sprouts, and broccoli are the same species and will cross. Brassica seed lasts many years when stored properly so grow one variety a year for seed. You do not need to grow every variety for seed every year.

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