Broadleaf herbicides like Roundup do not always work on tuberous rhizome weeds and often accidentally kill desired plants instead. ... Given the environmental and health impact of herbicides, it's best to avoid this approach.

How do you kill a tuber?

Apply glyphosate or halosufuron to the weeds when they're still in a growing phase. The chemicals will penetrate the tubers if the plant hasn't reached maturity. To control the weeds before they emerge, apply dichlobenil in areas with no grass.

Will Roundup hurt bulbs?

When you notice weeds in your daffodil bed after the foliage withers and dies, it's safe to spray the entire area. Roundup doesn't leach through the soil, so it won't hurt the bulbs if there are no living leaves above ground to absorb it.