Pre-emergent
Roy M. Sachs (Thu, 06 Nov 2003 10:12:21 PST)

Carolyn: Maybe this isn't the answer you want to hear, but, as with
all chemicals, it depends on which one you use, how much you use and
the bulb species in question. Many times the premerge hasn't been
tested on your species so that you have to do small patch tests to
make sure that there is no toxicity

I've had some bad experiences with a pre-emergent getting down too
deep in the soil and inhibiting root growth (my 'soil' is 90% clay
and root systems can be very shallow), but I've also had success when
I have had sufficient organic matter to bind the pre-emergent very
close to the surface. Again, it's a good idea to do a small patch
test.

I have used both liquid (Surflan/oryzalin)) and granular (again
oryzalin incorporated into granules) on alstroemeria; I prefer the
granular for ease of application and saving my back-pack sprayers for
other dedicated uses.

Big thing for mke is to remember where I used the stuff so that when
I return to replant I scrape away the surface soil containing the
premerge. Don't want that stuff around the roots!