Making Sense of Flower Bulb Size Info

You’re probably aware that bigger bulbs produce stronger plants and more flowers, and also tend to settle in better. Still, it’s sometimes hard to decipher the size info provided, to determine what’s larger and what’s smaller. Here’s a key to help.

Bulb Diameter

Calla lily bulb image

The diameter is the measurement across the face of the flower bulb. It’s often used for bulbs that have a flattened shape. The information may be presented in inches or centimeters.

Bulb Circumference

The circumference is the measurement around the outside edge of the bulb. Think about the information a tape measure provides when looped around the bulb.

"Top Size" Flower Bulbs

"Top size" isn’t really a numerical measure but rather a growers’ term. Flower bulbs are graded according to size and "top size" is how growers refer to bulbs that are oddly shaped and therefore hard to measure in a meaningful way. The “top size” group defines the largest bulbs that are commercially grown.

Sometimes size info is just provided as "6-8cm" without noting whether this relates to circumference or diameter. Not so helpful.

Flower Bulb Sizes Measured in Inches vs. Centimeters

In the United States, most of us think in terms of inches. However, many flower bulbs are grown and graded in Europe, where centimeters are the measure of choice. When both measurements are available, we provide inches and centimeters to aid in comparing offerings. (We work with growers to access the largest bulbs and encourage comparison shopping.)

If you want to translate centimeter measurements, it’s easy. Google can help. Just type in “convert inches to centimeters” and you’ll get conversion options galore.

Crocosmia bulb image

Seeing Is Often Helpful . . .

On this website, you can see what the plants and bulbs we ship look like.

On each product page there's an information grid. The last item is a "Planting Guide" link. Click over to that page to view examples of our product photographed next to a pair of Felco #2 pruners. These red handled favorites are about 8 1/2" long, for reference.