In article , Stewart Robert Hinsley
writes

Whether a plant becomes a pest or not depends not only on the plant, but
on the environment. A decorative plant may in some environments escape
from cultivation and play havoc with the ecology or the economy. For
example, Japanese Knotweed, Giant Hogweed, Himalayan Balsam and
_Rhododendron ponticum_ were all introduced to this country as
ornamental plants; they are all now considered weeds. It's quite
possible that a plant is a desirable horticultural object in one country
and a noxious weed in another.

This is very true. In the same way, plants which are generally
considered to be weeds can be welcome and useful in some gardens. I use
comfrey and nettles for composting, mulching, infusions etc., so those
plants are not weeds in my garden. I don't have to plant them or
cultivate them, they grow of their own accord. I clear them from areas
such as vegetable plots, flower beds etc. along with other unwanted
plants, but even there they return as compost etc. In the end there are
only two kinds of plants - natural and cultivated, and gardeners depend
upon both.
--
Alan & Joan Gould - North Lincs.