Hi All
Recently moved here and have a Pyracanthus growing UNDER some decking, thence out into the garden. It was obviously never planted there (who would be so stupid?), but is a sport. Its main stems are just about 8 inches in, under the decking, are old and gnarled, and impossible to dig out. I have cut it right back to about 4 inches, and know it will come again. Can't dig, so what will kill it. Would covering up the remains in black polythene prevent regrowth. Thanks for any suggestions at all. (And though it made a nice bush, it was pushing the decking apart.) Have never knowingly killed off a growing shrub before and it pains me to have to write this.
Caro
There are various stump killers on the market.
If you do not fancy them, then there are copper nails and or salt.
If you can drill as big a hole in the center of the stump and pour stump killer or other weed killer into the hole. Cover with clay to stop it drying out. Refill the hole every week or so. Sometimes using a weak solution of weed killer is better but you need to do it more.
If that does not work then keep sawing it back to the ground.
Good Luck
Bill
As well as the other suggestions I would try the black plastic after you have done them, but use some bricks to weight it down round the edge to stop all light if it sends out shoots which push up the plastic sheet.
I killed off (I hope) a pyracantha last year, it was growing through into a neighbour's fence in our new home, and couldn't be dug out. The stem was about 4 inches thick at the base.
I cut it down to about a foot high, scraped off most of the bark, painted on neat roundup.
It managed to grow some leaves in the summer, I painted them with neat roundup too. No growth after that, and can't find any green in the stem when I scrape it, but will keep an eye on it.