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Perennials/Bulb Sizes



When out shopping for flower bulbs recently, I found different bags of the same variety of daffodil, both growing to 24" high, but the bulbs in one bag were sized 10/12 cm and the other bulbs were 17 cm.  

What is the significance or effect of the different sizes of bulbs for the same type of flower?


ANSWER: Hello Ed,

In the world of bulbs, as you noticed, there are significant differences in size in the same kind of daffodil. And the effect can be quite dramatic.

Large daffodil bulbs will produce much larger flowers, and more of them. The 10/12 cm bulbs will bloom and produce, in probability, one flower.  But the 17 cm bulbs will produce two to three stems and multiple flowers. I have purchased both, and the difference is tremendous.

I should add that 10/12 cm is the basic standard for good companies and is acceptable. And the 17 cm is more expensive. But the larger bulb should give you a much better display. I have also noticed that you need far fewer of the larger ones if you want them to multiply. The large ones will multiply at a significantly faster rate.

Does this help? Please feel free to write again.


---------- FOLLOW-UP ----------

QUESTION: Thanks, that helps.  Another question comes to mind now -- if the smaller bulbs are planted, do they eventually grow to a larger size and therefore produce more blossoms as time goes on, or do they always stay the same size?

Hello Ed,

Yes, indeed they do, provided they are properly fertilized. In fall, when they are being planted, it is good to feed them with a slow release bulb food. It should not be too high in nitrogen in the nitrogen-phosphorous-potash mix. It should have a higher middle number, since phosphorous is good for root development. Any fertilizer labeled for bulbs should be good, with a ratio of, for example, 5-10-12.

If you really want your daffodils to develop faster, an additional liquid fertilization in the spring before bloom is helpful. Again, low nitrogen and higher phosphorous.

If you do this, the difference between the flowers the different bulb sizes produce will rapidly disappear. I generally buy the smaller ones, but once in a while a company surprises me with larger ones. If you take care of the smaller ones, they will definitely produce larger bulbs, and more flowers. The larger bulbs are simply the smaller ones, plus some time and feeding.

This is an excellent question!



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Donna Mack


I am a Master Gardener through the University of Illinois Extension.I can answer questions about pest control, especially voles, rabbits, chipmunks and slugs, and have done so on Dave's Garden Watchdog under the name DonnaMack since 2002. I have a lot of expertise with ornamental grasses, hardy roses and old garden roses, minor bulbs such as ornigothalem, chionodoxa and allium as well as most types of lilies. I lived in a conservaton community and have great familiarity with native plants. I am knowledgeable about organic methods and I grow perennials, annuals and vegetables from seed.


I have been gardening since 1998 and have raised roses, peonies, annuals and perennials (the latter two from seed), and numerous shrubs and trees, many of which I have planted. I am familiar with many organic techniques and use as many as I can but know the chemical solutions, which are most benign and how to use them. I LOVE gardening, and I get great satisfaction with helping others so that they reach the state of joy that gardening can bring to those inclined to it.

The American Lily Society and the Wisconsin Illinois Lily Society

I have numerous entries in Garden Watchdog under the name DonnaMack. I write three to four columns a year for the Kane County Chronicle. I also write articles for Daves Garden Watchdog.

I successfully completed the University of Illinois Master Gardening Program in March of 2013 and have maintained my certification every year since. I did this to augment extensive self study through books (I've probably read 100) and an arts degree, which helps with aesthetics. I am purely an amateur, but one who studies, reads, and documents extensively. My gardening log began in 2000, and has hundreds of entries, so that I can use my successes and failures to assist other gardeners.

Awards and Honors
The University of Illinois created a Team with Work Award for master gardeners who work together to create what they regard as an outstanding project. I won this award as part of a group that created "The Idea Garden", which suggests plants for home growers to attempt to grow. My personal contribution was salvias - ornamental and culinary hardy and tender perennials, which I grew from seed and tended through the season. I have recently been asked to join the Speakers Bureau, which would require me to present topics to various groups under the auspices of the Master Gardening program.

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I am currently overseeing and performing the maintenance of ten gardens in a suburbs of Chicago.

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