[APWG] woodiness in garlic mustard?

[David Schimpf]

In late April I found a single garlic mustard plant having two woody 
stems arising from a woody root.  This was in the far northeast corner 
of Iowa, surrounded by normal herbaceous garlic mustard rosettes.  The 
woody stems are each about 23 cm long and 8-12 mm diameter, fully 
suberized.  They were in a somewhat reclining position in the field.  
Each woody stem bore at its tip a large congested mass of leaves, all of 
which had the more rounded blades typical of the rosette stage.  There 
were some smaller dead stems attached just above these terminal leaf 
clusters of these large stems, which had remnants of fruits that had 
dehisced.

The plant was pulled out and moved to our university greenhouse, where 
it is potted. The leaf cluster on one woody stem died, but the other 
survived.  A new herbaceous stem grew from the base of the stem on which 
the terminal leaves died, but has stayed short and vegetative.  Three 
stems with the more triangular cauline leaf blades have grown from the 
tip of the stem that has the surviving terminal leaves, and started to 
flower/fruit in the past week.  A fourth flowering stem grew from below 
the soil line.

I am wondering if others have encountered garlic mustard like this. 
Might this be herbicide-induced?  One of the two woody stems is 
conspicuously flattened, and the other is terete.

I'll send a photo to individuals who request it.

-- 
David J. Schimpf
Associate Professor of Biology
Director, Olga Lakela Herbarium
University of Minnesota
Duluth, MN  55812-3004 USA