Question
Please advise if there is a way to kill forsythia bushes? I have removed part of the root ball and they keep growing back. I can't get the whole root ball out as they seem to be very deep with widespread roots as the bushes have been on the property 30+ years.

Answer
Hello Dena

Ridding yourself of Forsythia is incredibly difficult - as you've already found.  Getting rid of the stump may have just made a difficult task more difficult!

So - what to do?  If you can bear to let some of the shoots come up and into leaf next year, you could use a herbicide.  Once the leaves are fully open use the herbicide at about double the recommended strength, then do it again a week later and again a 7-10 days later!  This should do the trick, but is pretty heavy on the herbicide.  It isn't something I'd like to do myself, but if needs must ........

Alternatively you could spread Epsom salts over the exposed roots and cover with soil.  I'm told this works, but as I've never tried it, I can't vouch for its effectiveness.

An old method a clearing a site of unwanted growth is to do what you have already done, apply herbicide to the area and then cover the site with something to keep out the light.  Old carpet used to be recommended, but it's pretty unsightly, so horticultural liner is recommended these days.  As long as it's dark in color to keep out the light it doesn't really matter and you can cover it with pea-shingle or something similar for the sake of appearance.

I have to warn you though that the final demise of this plant will take some time!!  Forsythia is a toughie!!

Gill