Can edible chestnuts be planted in close proximity to non edible chestnuts? Will they cross pollinate and spoil the edible variety?
I am not aware on any inedible chestnuts. If you are talking about Aesculus hippocastanum (horse chestnut) it is in the soapberry and lychee family Sapindaceae and not the Fagaeae family as true chestnuts are. In fact they are not even related in any significant way.
Horse chestnut (not true chestnuts) pollination and flower fertilizations takes place in the spring, true chestnuts shed pollen and are receptive in the summer, so in addition to cross species pollen incompatibility they are not receptive at the same time.
You can read more here http://msue.anr.msu.edu/news/whats_the_difference_between_horse_chestnuts_and_sweet_chestnuts
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