Buy the 2015 Old Farmer's Almanac!
its a good question for aits a good question for a beginner. one per plant is because it is a root we are after, similar to carrots and they usually only grow one. rarely, i have had double or triple beets and up to six on my carrots but usually just one. items like that are best from seed. much cheaper and do much better. good luck!

Shop Wind Bells in the Almanac General Store