I have grown D.brevifolia for a number of years now. As with
much of my stuff the original plants were grown from seed
with the location details 'El Pinar Uruguay' - did you
collect this stuff Fernando? My experience has been similar
to Daves in that my plants have persisted after flowering
also despite setting seed. Hope this helps.
Fernando I hope to drop you a letter in the next day or so
my time permitting.
Kind regards
Loyd