Many species occur as unwanted weeds in gardens. Among the commonest or biggest nuisances are:
| Ground elder | Aegopodium podagraria |
| Cow parsley | Anthriscus sylvestris |
| Thale cress | Arabidopsis thaliana |
| Daisy | Bellis perennis |
| Bindweed | Calystegia sepium ssp. sepium |
| New Zealand bittercress | Cardamine corymbosa |
| Hairy bittercress | Cardamine hirsuta |
| Couch grass | Elytrigia repens |
| New Zealand willowherb | Epilobium brunnescens |
| American willowherb | Epilobium ciliatum |
| Common horsetail | Equisetum arvense |
| Hogweed | Heracleum sphondylium ssp. sphondylium |
| Creeping buttercup | Ranunculus repens |
| Broad-leaved dock | Rumex obtusifolius |
| Groundsel | Senecio vulgaris |
| Dandelion | Taraxacum officinale |
| Nettle | Urtica dioica |
Many exotic shrubs introduced for garden purposes have become nuisances both within gardens and in the wild. Notorious examples are rhododendron (Rhododendron ponticum and its hybrids), pirri-pirri bur (Acaena ovalifolia and allied species), snowberry (Symphoricarpus rivularis), Japanese knotweed (Fallopia japonica).
| © National Museums and Galleries of Northern Ireland and Environment and Heritage Service, 2000-2004 |