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Post by robertb on Mar 12, 2011 9:12:23 GMT -5
I'm wondering what techniques people use when growing brassicas out for seed, to prevent crossing. I can grow out two broad beans, say, at opposite ends of the allotment, and they don't cross. I'm not sure that would work for cabbages though. I can do two varieties a year by covering them with netting on alternate days, but what other methods are there?
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Post by Joseph Lofthouse on Mar 12, 2011 13:05:12 GMT -5
I'm wondering what techniques people use when growing brassicas out for seed, to prevent crossing. I can grow out two broad beans, say, at opposite ends of the allotment, and they don't cross. I'm not sure that would work for cabbages though. I can do two varieties a year by covering them with netting on alternate days, but what other methods are there? How many days of pollination do you actually need to set enough seed for your needs? Would one day in 5 be sufficient? What is your purpose for segregating? Can your desire for low genetic diversity be achieved in other ways such as by rouging out off-type offspring? What level of diversity can you tolerate? Out-breeding pollination approximately obeys an inverse square law... Meaning that as a first approximation a plant is much more likely to be pollinated by it's closest neighbor than by the plant at the end of the row. To throw some math into the mix. Lets say we have a row of cabbage 20 feet long. The chances are approximately 400 times greater that the plant on the end of the row will be pollinated by it's closest neighbor that's only a foot away than by the plant on the other end of the row. And if our two cabbage patches are separated by 100 feet then chances are around 10,000 times greater that it will be pollinated by it's closest neighbor than by a plant from the other patch. Commercial growers use this to their advantage. They'll plant sacrificial rows of corn around the outside of a field. These are not saved for seed, but provide gobs of pollen to drown out any tiny amount that might be blowing in on the wind. In smaller gardens we can plant in square patches rather than in long rows to take advantage of this effect. You could grow the cabbages in alternating years and produce enough seeds for several years. You could put a barrier between your two cabbage patches such as a house, or a hedge to slow down the pollinators. For my purposes, I figure that if I plant a large patch of the same species all together, that it is isolated if I don't plant another patch of the same species within 100 feet. Then when I plant the seed if I see anything I don't like I chop it out.
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Post by Leenstar on Mar 12, 2011 19:18:27 GMT -5
I have only grown out kale for seed. it was more of an experiment dealing with biennials. Most brassicas are biennials and you can segregate by time. You should be able to alternate cycle from year to year different seeds. Grow one out for seed per year. When I grew my kale out for seed it was at a community plot. The section I was in was not a section here people could over winter things. I was pretty sure that all the surrounding plots, even if they had planted a brassica wouldn't have theirs in going from the second year. I had gotten around this as i was new to this plot and transplanted stuff from my old plot into the new plot after it had over wintered.
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Post by robertb on Mar 13, 2011 14:13:06 GMT -5
I've got so many rarities I need to do at least two a year or I won't keep them all going. Once I've raised seed of all of them, and shared it around, I'll feel happier. My plot's less than a hundred yards long, and I keep bees on it. They love brassicas, and of course they target particular species. So I'm being very careful! I'll probably do two and net them alternately. Three might be better, if I can find the space and still get decent pollination that way.
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Post by extremegardener on Mar 18, 2011 9:39:14 GMT -5
I can do two different kales a year by letting the earliest-bolting one bolt and harvesting the buds on the other one to eat, then when the early one is done flowering, let the other one bolt. It's not the most ideal for the second kale because it robs some energy from the plants that would otherwise go to make seed, but if you harvest the buds small (they taste best that way, anyhow) it's not too much of a drain. Also, you have to stay on top of it and be sure not permit any of the second kale to bloom until you're ready. You can also throw a row cover over the first one if it's set a good amount of seed but is still blooming and you want to let the second one start blooming.
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Post by robertb on Mar 18, 2011 12:37:07 GMT -5
Thanks; I wasn't sure whether that would work. Between that and covers, I could get two, probably three varieties off my plot in a year. More than three would take unreasonable amounts of space from my other crops. When do you find the seed ripens?
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Post by extremegardener on Mar 18, 2011 14:52:56 GMT -5
The bolting seems to vary according to the variety. My Russian Red type grex has filled out green pods around solstice, and seed mostly dry in the garden mid July. I sometimes have to pull the plants early to mature in the breezeway if our weather is not cooperatively dry enough, also to avoid loosing too much seed to shattering when that's a concern. (I usually like a little shattering to make volunteers.) The Siberian-type if left to its own devices usually begins bolting about 10 days after the Russian Red type. I have a blog post about this: theextremegardener.com/?p=86
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Post by robertb on Mar 23, 2011 14:11:37 GMT -5
Interesting post. What's a breezeway?
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Post by extremegardener on Mar 24, 2011 13:05:08 GMT -5
Interesting post. What's a breezeway? Oh - a roof connecting house and garage, open on two sides, 20 ft long and wide enough to pull a car into. It's my main drying area.
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