In the auctions in Holland, flower bulbs are gauged by their calibre, or the measurement of the bulb’s circumference. For each particular variety: more mature flower bulbs are larger and garden bigger flowers. These demand a higher price. For high-profile bed plantings, it’s worth the higher price for the more mature, ”showier” flower bulbs. But younger (smaller calibre) flower bulbs, which are often sold at lower prices, can offer a great way of adding colour to large areas or marginal areas of the yard where they can be left in place to naturalise and mature, thus gaining in size over time. A note: for quality control reasons, the Dutch do not export flower bulbs below certain established calibre’s. For instance, tulips must be 10 cm or larger or the Dutch will not export them. This means that if you see tulip bulbs for sale that are smaller than 10 cm, they are not from Holland. No exceptions are allowed… except for species tulips, which are naturally sized smaller.