Q: Help! An invasive weed with wire-like roots is taking over my shrub and lawn area. I have tried digging out large amounts of the root. I have also tried using Roundup, but it seems to only temporarily kill the top growth. Is there a systemic that I could use which would not only take care of the top growth but also the roots? Any suggestions please?
I will assume this is goutweed (Aegopodium podagraria), which spreads by roots and is dormant in winter. A quick way to identify goutweed is by scent - a broken piece of the plant smells like celery. Mulch the shrub bed using coarse wood chips, similar in texture to a tree that has been put through a wood chipper. Ensure the layer of mulch is 15- to 20-cm-deep (6- to 8-in.) and maintained year round. Coarse wood chips at this depth should not hinder your shrubbery but will still smother out the weed. Continually clip the weed tops. This combination will eventually weaken the root system.
For your lawn, ensure frequent close mowing and periodic overseeding with grass seed. Overseeding will thicken the existing grass and smother out the weed. Be patient and persistent - remember the weed did not appear overnight. Systemic chemical (“Roundup/Wipeout”) will be absorbed into the weed roots to a certain length but not necessarily all the way. Chemicals may result in damaging other desirable plants and are not necessary for eradication.