Answer: The black mulch encourages the soil to warm up faster and thus may be important in getting the artichokes off to a good start and help provide a longer season of active growth for them. This is important in short season areas (as compared say to California). The red mulch has not been tested on artichokes that I can find reference to in a quick search. (It has been tested extensively with tomatoes, peppers, muskmelons and zucchini.) You might try an experiment and see which works better, but my hunch is that the black would be preferable at least early in the season.
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