How To Deal With Problem Plants

There’s a range of popular ornamentals that can cause problems, says Tim Rumball

- Tim Rumball

It pays to know your enemy. Most gardeners will be able to identify weeds like couch grass, horsetail, ground elder and the dreaded Japanese knotweed, but there are lots of pretty ornamental plants that will happily run riot in our gardens.

One of my own big mistakes was sowing a few seeds of the attractive Welsh poppy (Papaver cambricum). It looks like an annual, but is a hardy perennial that self-seeds everywhere. I still get this wolf-in-sheep’s-clothing popping up more than 20 years since I started to grub it out. It loves my sandy, free-draining soil and self-seeds among clumps of other plants. The only sensible way to get rid of it is to seek out the palegreen foliage, then dig beside it deeply to lever out the long taproot. Similar selfseeders like Verbena bonariensis and the wild violet (Viola odorata) are easy to control in comparison.

Pesky bamboo

Peter Seabrook’s article about clearing a jungle of bamboo (AG, 8 August) struck a particular chord when a friend asked me to help him take out a clump about 6ft (1.8m) across. He’d cut the tops down, and we both worked at it, hacking and digging for most of a day and still didn’t get all the roots out. He built a patio over the top of it and hopes it won’t reappear.

A slower but easier way to deal with bamboo is to cut the stems down to about 6in (15cm) and fill the hollow tubes with a systemic glyphosate weedkiller, such as Roundup or SBK Brushwood killer. You won’t be able to plant in the space for several years, until the root has rotted away, but it will save a lot of backbreaking work. If the clump is in an isolated spot away from fences and buildings, you might be able to build a bonfire over it and cook the roots to kill them. I’d advise never to grow any bamboo (clump-forming or otherwise) in the soil, only in a large pot.