How Does A Colchicum Know When To Bloom?

– Posted in: Colchicums
7 comments

I‘ve grown colchicums for more than two dozen years. I’ve tried more than two dozen kinds, and I still grow most of them. I’ve read everything about colchicums I could get my hands on. But there’s still one thing about them I don’t know and would like to: what combination of factors induces them to bloom?

This year I noticed that the first several varieties emerged on the same day, September 3rd, after a night of rain. Did the sudden onset of moisture cause them to bloom, or was that just a coincidence?

first colchicum bloom 2013 and 2014

Last year, Colchicum autumnale (left) was the first to bloom on September 2. This year it hasn’t even emerged yet. ‘Beaconsfield’ (right) was one of several varieties to emerge on September 3rd this year.


The more I think about it, the more I realize that the interrupted life cycle of colchicums complicates things further. The leaves emerge in spring, and can be affected by soil temperature, air temperature, and moisture. I’ve noticed that when we have a wet, cool, spring, the leaves hang around a lot longer.
Colchicums are hard to love when they're going dormant.

Colchicums are hard to love when they’re going dormant.


Then the corms are dormant–or seem to be. But they could still be affected by soil temperature and moisture.

And usually in the first week of September, the earliest blooming varieties start poking through the soil and opening up. Occasionally, though, they start the last week in August. Why? This year, they started blooming on August 24th for my friend Carol, who lives in Indianapolis, a climate warmer but not necessarily drier than mine. That’s almost two weeks earlier!

Carols early colchicums

Carol’s colchicums started blooming two weeks earlier than mine! Why? (Photo courtesy Carol Michel and used with permission)

And of course, corms that were recently planted bloom later than they do once they’ve settled in.

Lysimachus  colchicum 2014

I planted ‘Lysimachus’ last year and it bloomed September 17th. This year, September 3rd.


No one but a rabid colchicophile would even ponder such a thing. Still, if you’re curious about when all my colchicums bloomed last year, I wrote a post every week about the new colchicums that were blooming. You can follow along on what I called the colchicum patrol.

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

Autumn is a second spring when every leaf is a flower.

~Albert Camus in Albert Camus quotations

Comments on this entry are closed.

Elena October 16, 2014, 9:48 am

Off topic:
I have given as a gift an Amaryllis (Red Lion) to my best friend in Canada. The flower it developed was incredibly beautiful. It was three years ago. Since then it did not bloom again. We tried so many tricks on the poor bulb and it is so stubborn. Is it possible to get some advice, please, what to do? Now, it has two leaves since August. We can’t unearth it and place in the fridge because of it. It might be of help if I can find another blogger who writes about this flowers too.
Thank you.

Kathy Purdy October 16, 2014, 9:57 am

Elena, many people say that Amaryllis only bloom well once and then should be thrown out. Others say you can keep them going for years. But Amaryllis are native to warm areas and should never be put in the fridge. They need a dry period before they bloom. You just may have to withhold water and let those leaves wither and die, and then start watering again. Here is a helpful link: http://www.usna.usda.gov/Gardens/faqs/AmaryllisBloom.html

Frank September 17, 2014, 7:43 pm

Mine are starting to bloom right now in a hard, dry, sunny spot and I can’t for the life of me figure out why they wouldn’t wait for a little rain to come along. I guess they have to get blooming in before it gets too cold, but it sure makes me feel guilty for not watering more.

Kathy Sturr of the Violet Fern September 15, 2014, 6:29 am

I have yet to add these to my garden and every year right around now I wish I would have! It seems when I order bulbs – and I order early – they are always already sold out! Someday … then I can try to figure out what entices them to bloom!

Donna@GardensEyeView September 13, 2014, 8:59 am

Mine just started after very cool wet weather.

Layanee DeMerchant September 13, 2014, 7:06 am

My colchicums appeared the day after a rain and while I was sleeping . They seem to pop us like magic. I have one from you and I call it ‘Kathy’s colchicum’. It always makes me smile.