Question
QUESTION: Hello:

My mother (in Pa.) has an area where she would like to plant some spring flowering bulbs.  There are currently weeds there.  I bought some weedkiller (Roundup) to spray on the weeds.   

Would it be better to apply the weedkiller before the bulbs are planted, or afterwards?  (The bulbs need to be planted soon, due to the weather, so there would probably only be several days between each action.)

Thanks.

ANSWER: Hi Ed, I would apply first.  In the process of planting, you will cut some of the weed roots.  These might re-sprout.  Spray first, give it as much time as you can to circulate through the weed and then plant.  Glyphosate cannot be absorbed through roots, so even after the bulbs sprout you can paint weeds with it using a sponge or paintbrush and not hurt the bulbs as long as you don't touch the foliage.  Jim

---------- FOLLOW-UP ----------

QUESTION: Thanks.  That's what I was concerned about; either way, the weeds would be disturbed to some degree.  Do you have a general idea how long the chemical takes to go from the leaf to the root, so that even if the weeds are cut after spraying (while planting the bulbs), the chemical would already be in the root to kill it from regrowing?  I'd like to plant as quickly as possible, but also give the chemical enough time to circulate throughout the weeds.

Answer
It depends.  At 90 degrees in the sun, about a day.  With cloudy skies and a soil temperature in the 40's, it can be a week or more. It just depends on how quickly water is moving through the plant.  The sunnier and windier it is, the quicker the results.  This time of year, I'd give it at least 3 good sunny days and then plant.  Then follow up applications as we discussed earlier if needed.  Jim