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