Nell wrote:

On a large property I have about a dozen foxglove plants at the moment,
all with dark purple flowers and they are beautiful and charming. They
popped up in various places in the early spring along with the weeds and
I plucked many out recognising them immediately, but I left those that
had appeared in attractive or bare positions.

I prefer to have a mixture of colours from white to purple. YMMV

This weekend the previous owner revisited and warned that if I don't
pull this dozen out immediately, the whole property will be covered with
them next year. He says that he spent years trying to get rid of them.
How true is it that they will become a frightful nuisance?

They are not a real problem in a big garden provided you only let them
grow where you want them (and remember to cut the seed heads off before
they ripen). I expect if you left all the seed heads on it could rapidly
get out of control since each plant produces a few thousand sseds...

As I drive along country roads and lanes I see a few here and there,
never more than a dozen every half mile or so. If it were true that
they can run riot, I can't see why the verges aren't full of them.

There are other things that compete even more aggressively in the
hedgerows. On cultivated ground it is different. I have never found
foxgloves much of an issue they are so easy to hoe out when small.

Regards,
Martin Brown