corm; was RE: Late fall in Maryland

Adam Fikso
Mon, 14 Dec 2009 09:57:54 PST

Well, I don't know if this a criterion, but I've always considered that to 
be a corm, the part should be roughly radially symmetrical,, e.g,. gladioli. 
Tubers are not much so, necessarily, e.g., potatoes, dahlias, yams, and more 
rhizomatous, with some arisaema tubers being roughly radially symmetrical, 
and tending to be symmetrical around a vertical axis--with tubers not 

----- Original Message ----- 
From: "J.E. Shields" <>
To: "Pacific Bulb Society" <>
Sent: Monday, December 14, 2009 10:13 AM
Subject: Re: [pbs] corm; was RE: Late fall in Maryland

I looked both terms up in the glossary of John Bryan's "Bulbs" revised
edition.  I don't always blindly trust John, but he did have help putting
that volume together.

Corm -- underground storage organ, a swollen part of an underground stem

Tuber -- underground root modified as a storage organ.

The modifier "underground" seems to eliminate pseudobulbs and other
above-ground structures.

I myself have a hard time distinguishing some tubers from corms.  I tend to
think of corms as annual or at most biennial structures and tubers and
bulbs as perennial structures.  Is that reasonable?


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