For next season, how many medium supers should I purchase/plan for each hive? Some sources (websites) say three, others mention up to seven. My site is on semi-arid colorado plains with plenty of yellow clover.
Well if you have lots of clover, I would have at least equivalent to three deeps ready. I usually pull mine three times a season.
I never hurts to have too many. In an awsome year you might need five or more supers per hive. In a miserable year you won't need any.
Ask around your area what the average crop per hive is per year. If you only extract once you will need enough supers to hold that average, and as Michael says, in a bumper year more. I figure an average full medium holds thirty pounds of crop. I almost always need five mediums per hive. Some fill nine, some fill none, some fill a few partials and a few fulls.
One can never be too rich, too thin,
or too well stocked with drawn comb.
Having "too much" means that you can
"retire" and recycle brood frames,
replacing them with drawn "honey frames".
Too little, and you are losing valuable
Stack half a dozen mediums on a colony, and
even though they might "make" only 3 full
supers of honey, they are able to dry the
nectar down to honey faster due to the
larger amount of comb, and resulting larger
exposed surface area from which to evaporate
water. There are also studies that proved
that bees presented with larger amounts of
drawn comb tended to gather more nectar than
equal-sized colonies presented with less