From jackrowe@compuserve.com Mon Jun 14 11:42:40 1999 Date: Mon, 14 Jun 1999 09:15:27 -0400 From: Jack Rowe Reply-To: Seed Saving To: Seed Saving Subject: [seed-saving] Cross-pollination in flower varieties [ The following text is in the "ISO-8859-1" character set. ] [ Your display is set for the "US-ASCII" character set. ] [ Some characters may be displayed incorrectly. ] Ute, I think the Calendulas will cross, and being Compositae are bee pollinated so up to a mile might be needed for isolation. 1/4 mile is a more probable useful figure. Bees travel farther to forage in areas where available forage vegetation is sparse. . . two plantings in a densely-vegetated area separated by a 100-foot field of yellow flowers might be perfectly safe. Bee foraging patterns are complex, and territories don't overlap so under some circumstances (barriers to bee travel, flight patterns of bees, territory boundaries) a very short distance could be enough for isolation. Pretty vague and difficult to quantify or give definite boundaries, plus the bee populations could change from one year to another. Larger plantings are safer from crossing, too, since individual bees will likely get their foraging fill in one group of plants before needing to venture into a neighboring planting. Also, in larger plantings, seeds taken from nearer the center of the planting will be purer. These facts are true of wind-pollinated plants, too. A little crossing below the threshold of major changes tends to invigorate a given population, so absolute purity is not always a desirable thing. Take dogs and royalty as good examples of this fact. Fairly uniform characteristics can be maintained by 'roguing', or preventing 'off types' from flowering after their 'offness' is noticed. Roguing is fairly common among pepper growers, who sort-of-safely ignore adequate isolation distances and then later take advantage of the tendency for peppers to cross at only 5% - 10% or so, being self-fertile and mostly self-pollinating. Taking over a group of peppers not carefully isolated by their previous caretaker for about 3 years, I found only one variety which was thoroughly confused after this period of time. Most had maybe 15% off types. Furthermore, there were some interesting 'new' types among the peppers I ended up with and some good selection experiments could have been carried out. If you've grown sunflowers you probably know that the Composites can cross a lot more rapidly than this, though. For truer maintenance of characteristics, take advantage of properly-dried seeds' storage capabilities and just grow only one variety from each species each year in an alternating cycle. Or use 'time isolation' if you've a long growing season, letting the earlier variety produce a good seed crop before the second is flowering. Any opinions I'd have on the Nasturtiums would be even more speculative, so I'll refrain from wilder guesses. Seed trade associations might have access to the information you seek -- you'd likely have to be a member to pry it from them (e.g. American Seed Trade Association, http://www.amseed.com/index.html; Canadian Seed Trade Association, http://cdnseed.org/index.html). Good luck, please let us know any interesting results! Jack Rowe Seeds of Texas Seed Exchange http://csf.colorado.edu/perma/stse/ --- You are currently subscribed to seed-saving as: london@metalab.unc.edu To unsubscribe send a blank email to leave-seed-saving-78045J@franklin.oit.unc.edu