I have seen no ill effects from using Roundup over completely dormant bulbs. In fact, last year I had to get rid of a very invasive subshrub (Rosa sp.) and I used Crossbow on it over dormant bulbs with no apparent damage. However, before I sprayed the Crossbow, I covered the sites of the bulbs (colchicums, mostly) with a thick layer of bark mulch, which I later removed. Jane McGary Northwestern Oregon, USA