At the auctions in Holland, flower bulbs are graded according to their circumference which is then referred to as their bulb size. For each particular variety, the more mature flower bulbs are larger and will produce larger flowers. These bulbs demand a higher price. For high-profile bed plantings, it’s worth the higher price paid for these more mature bulbs that will produce a showier display. But younger (smaller-sized) flower bulbs, which are often sold at lower prices, can offer a great way of adding color to large areas or marginal areas of the yard where they can be left in place to naturalize and mature, thus gaining in size over time. It should be noted that, for quality control reasons, the Dutch do not export flower bulbs smaller than certain established sizes. For instance, tulips must be 4 inches in circumference or the Dutch will not export them. This means that if you see tulip bulbs for sale that are smaller than this, they were not exported from Holland were no exceptions are allowed except for species tulips, which are naturally smaller in size to begin with.