plants that react badly to trimming

[Cavan <millsman7 at yahoo_com>]

One of my conversations with Claus at the convention
was about why some plants suffer and sometimes even
die after being trimmed and replanted.  Rotala
macrandra was mentioned.  It frequently grows very
tiny leaves before recovering when replanted.  I know
we've talked about this before, but I don't think we
reached a consensus about what's going on there.  

Claus said that it has something to do with nutrient
transport within the plant being disrupted.  I guess
that makes sense, but I know of people who don't have
that problem.  I haven't grown it in a while because I
got tired of dealing with it.  I could get it to grow
deep red and very fast but couldn't get around the
trimming problem.  

I have some of that Blyxa sp. "Vietnam" (may be
alternifolia) that's going a little nuts and spreading
all over the place (no requests for now please).  The
first time I had it I trimmed it when it got to the
surface.  It promptly stunted and died.  This time I
haven't hardly trimmed it at all.  I just push the
stems down and weight them with rocks.  That's getting
old though, and it's tough to make things look nice
that way, especially when it starts showing up across
the tank in the middle of something else.  

Some side shoots that grew their own roots did
survive, but I doubt they would make it if I just
replanted a top without roots.  

Some things I'm wondering:

- How much does the "has its own roots before planting
thing" have to do with it?  

- Might water hardness have anything to do with it?  I
wonder if it would be as much of a problem in softer
water (it does seem to better in that).  

Thanks, Cavan

PS  Can anyone tell me anything about the true
identity of the Blyxa I'm talking about?  Origin and
habitat?  I think it's the same stuff that Jeff Kropp
has.  It spreads through runners.  Stems are long and
sparse except near the top, where there are a lot of
leaves and almost no internodes.  It is NOT japonica
(like the stuff in Jeff Senske's gallery tank).  Grows
pretty tall.     

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