When siting your apiary, you are trying to achieve maximum sunshine and wind protection, entrances that face east or southeast, convenient access for the beekeeper, etc. and it's just not always possible to achieve all of these in the same location. Luckily, sometimes problem summer shade disappears in the critical winter and spring breaks because the offending vegetation is deciduous! The leaves fall off the trees in winter, allowing your bees to take advantage of those precious sun breaks for cleansing flights, reducing the risk of dysentery.