"Rogues Gallery" of Perennial Weeds

Couchgrass foliage.

Couchgrass Roots. These are often far longer than those illustrated here. Generally though they are shallow, in the top 30cm (12") of soil.
Dockleaves. Shown here gone to seed. Their roots are long taproots stretching down to 60cm (2'), in contrast to the spreading rhizomes of couchgrass.

Brambles. These woody colonisers of unused land require more physical effort to eliminate than smaller plants, but can be cleared more quickly.