Bulbs and pre-emergent herbicides

[janemcgary]

I'm in the process of renovating a part of the bulb lawn. Near the street where people park weed-dispersing cars, it acquired an infestation of Geranium lucidum (shiny geranium) that could not be stopped except by killing the whole area. I'm thinking of applying the persistent pre-emergent Casoron now and having the area covered with a bark mulch, then waiting to see if the weed reappears next spring. If it doesn't, I'll replant with low shrubs and bulbs. Does anyone know how Casoron might affect bulbs planted about 14 months after application?

[MarkMazer]

 "applying the persistent pre-emergent Casoron now and having the area covered with a bark mulch"


Would not the bark mulch extend the herbicide's soil persistance past the often quoted 10 months?

Mark Mazer
Hertford, NC

[janemcgary]

Interesting question. The site is sloping toward the street, so runoff might decrease persistence of Casoron. However, the bark itself would be a good home for wind-dispersed weeds from the unmaintained lots across the street. Perhaps I should just leave the eyesore for a year (no neighborhood committee here), then replant with inexpensive bulbs and seed some shade- and drought-tolerant grass over it. It's going to be summer-dormant whatever I do because of huge Douglas firs nearby. I surrounded the trees with Cyclamen hederifolium, which is effective about 9 months a year in a gravel mulch.