Are you confused by circumference numbers, grade names and code words on tulip bulbs? It’s no wonder; who doesn’t want to look at a bag first thing in the morning and know exactly what they’ve purchased?
The number refer to equatorial circumference (that is, around its middle) measured in centimeters. The higher the number, the larger amount of food reserve contained within the papery skin of the bulb, meaning more energy for stem, roots and blossom. And here’s a comparison chart to get an idea of relative sizes: A 12 cm tulip isn’t as big than a 20 cm allium.
How to Read Tulip Bulb Labels
Match the bulb’s stored energy to what you expect it to do. Expecting a small (bedding-grade) tulip to grow as tall as a cut-flower variety? It won’t. It doesn’t have fuel or even the structural strength to get that high on a stem. Its size grade tell you how well it can performs. No need to fault the soil if the thing just doesn’t has the resources to be any bigger.
Depending on what time of year they are being planted, you may also see various label markings: DN1 (a specific code used for daffodils), or a one number marking around the circumference, for instance, spring bulbs like those planted in fall tend to be marked this way; whereas summer plants like glads and lilies, for example, tend to have two numbers (like 16/18) indicating the pair of bands around the circumference, which represents range of sizes within that particular bag. It is the same thing expressed differently. That means reading the label right so you don’t end up with a package of undersize corm when you wanted bigger bulbs for something that stands out.
How deep? As a general rule, plant according to size of the bulb: The deeper than twice the bulb’s height it is planted, the better (though again not if the grade won’t cooperate). That means a little crocus gets proportionate depth, and so on.
But here’s where the grade comes into play: If you’re looking for 100 percent bloom the first year, larger bulbs are more likely to bloom, while smaller bulbs is less likely. Top-size bulbs has enough energy to establish roots and produce a flower all at once. Bulbs in lower grades tend to use their energies first on establishing roots; many skip flowering to stay alive. Growers don’t realize that. They want bulk, cheap, and wind up with just green foliage and no flowers.
Selecting the grade means getting real about your expectations: Do you want impact now? Then pay up for the bigger circumference. Are you making a naturalized area, where you don’t mind waiting a year or two while things get established? Then go small; it’s all good value. It is a choice between price and patience. That’s the trade off, and the infographic helps make clear how much the success depends on having those reserves of energy in the ground.
Next time you’re leafing through your catalog, beyond the photo of the bloom, focus on the centimeter count. That’s what’s underground before you turn over the first spade. Order the size whose timeline fits yours, and then enjoy the flowers as they arrive.