This perennial forms a low mat of dark green leaves. Dig up young plants before they flower, or cover them with weed matting or carpet. If they persist, treat repeatedly with glyphosate weedkiller.
The cloverlike leaves spread rapidly, and can invade lawns. Annuals have explosive seed pods; perennials have bulbils. Yellow oxalis in lawns resists selective weedkillers, so try scarifying in autumn.
The roots of this perennial are hard to pull out since the stems snap easily. A water-resistant coating on the stems also helps them shake off weedkiller, so crush them before treating with glyphosate in late summer.
Treat plants when young: dig the taproot out with a fork, or use a weeding tool in lawns. Don't allow mature plants to flower, and use a glyphosate-based weedkiller to kill their extensive root systems.
Perennial stinging nettles form a network of root runners that support a colony of plants. Wear thick gloves to dig out the whole root system, or spray with systemic weedkiller. Or leave large groups for a valuable wildlife refuge.
Any root fragments of this bamboolike thug will regrow. Repeatedly dig them out over several seasons; dry and burn the removed roots. If this fails, spray with glyphosate-based weedkiller repeatedly from late spring to early autumn.
This pretty but persistent twining perennial disappears in winter, only to resprout from fleshy white roots in spring. Digging it up can spread the roots; instead, train it up canes set away from ornamentals, and spray with glyphosate.
The thorny stems spread rapidly over other plants and the tips will root wherever they touch any soil. Dig out seedlings and rooted runners. Cut back larger plants and dig out the woody base and roots. Spray unplanted areas with brushwood killer.