Garden Thugs © Frances Michaels

This is a list of garden plants best avoided unless particular care is being taken to control their spread. The plants in the first list are not usually classified as 'weeds', they simply take far too much time and effort to keep in their place. Many of them are sold as 'herbs' and have a range of uses. The rampancy or vigour of a particular plant is very much related to the area you live in. Plants that can be well-behaved in one area can become serious weeds in a different climate zone. This is a particular trap for gardeners that relocate north to a warmer area. Plants that had previously behaved well suddenly either drop dead in the wet season or become garden thugs. The Sky Flower vine which is a reasonable performer in Sydney, tries to take over bushland in Cairns. Elderberry, which is just a shrub in Victoria, can grow into a large, suckering tree thicket in Queensland.

As organic gardeners we need to choose plants that are suitable to their environment, as their water needs will be less and they will be far more resistant to pests and diseases. The impact of growing plants outside their preferred zone is huge (wasted water, pesticide usage, even glasshouse heating costs). However, plants well-adapted to the climactic zone you live in will generally reproduce. The real question is, how much is too much? A seedling here or there might not be a problem with annuals such as basil or parsley, as they tend to come up close to where they were growing the previous year. However, plants that birds eat the fruit of, can quickly become a serious problem as birds will spread them far and wide. Fruit trees such as olives Olea europaea are now a problem in South Australia. Ornamental shrubs with berries that are fast becoming a problem in Queensland include Mock Orange Murraya paniculata, Duranta and Indian Hawthorn Rathiolepis spp.

Some of the most widespread 'weeds' in Australia are the invisible ones, the ones we see as just 'green paint' on the landscape, the grasses. If your garden or property doesn't already have a carpet of kikuyu Pennisetum clandestinum (E Africa) couch Cynodon spp, carpet grass or buffalo grass Stenotaphrum secundatum (Africa) then for goodness sake, don't plant any!

Garden plants best avoided:
Aerial Potato Discorea bulbifera
Balsam syn Busy Lizzie Impatiens spp.
Buddleia syn Butterfly Bush Buddleja davidii
Chinese artichoke Stachys spp.
Chinese Forget-Me-Not Cynoglossum amabile
Cleavers Galium aparine
English Ivy Hedera helix
Epazote Chenopodium ambrosioides
Fennel - Common Foeniculum vulgare
Fish Plant Houttuynia cordata
Gazania Gazania spp.
Ginger Lily Hedychium gardnerianum
Guava Psidium guajava and P. guineense
Horehound Marrubium vulgare
Yellow Water Iris syn Yellow Flag Iris pseudacorus
Lavender - Spanish syn Topped Lavandula stoechas
Leucaena Leucaena spp.
Lippia Phyla nodiflora
Mint Mentha spp. (particularly Apple mint, Eau de Cologne mint). Mints are best planted in large tubs, positioned under or near taps, to avoid them taking over large areas of the garden.
Mirror bush Coprosma repens
Mugwort Artemisia vulgaris
Paris daisy Euryops abrotanifolius
Pink Evening Primrose Oenothera spp.
Pink periwinkle Catharanthus roseus
Sky Flower Thunbergia grandiflora
Yarrow Achillea millefolium

Garden plants which are definitely weeds, however you look at it, including some very serious ones:
Arum Lily Zantedeschia aethiopica
Asparagus Fern Protasparagus densiflorus
Blackberry Rubus vulgatis
Black-eyed Susan Thunbergia alata
Blue Periwinkle Vinca major
Blue Potato Vine Solanum wendlandii
Bridal creeper Myrsiphyllum asparagoides
Broom Cytisus spp.
Cape Ivy Senecio angulatus
Cat's Claw Creeper Macfadyena unguis-cati
Coreopsis Daisy Coreopsis lanceolata
Cotoneaster Cotoneaster spp.
Duranta Duranta repens
Fishbone Fern Nephrolepis cordifolia
Fountain Grass Pennisetum setaceum
Glory Lily Gloriosa superba
Golden Rod Solidago altissima
Honey Locust Gleditsia spp.
Honeysuckle Lonicera japonica (some cultivars are well-behaved)
Horsetail Equisetum arvense
Japanese syn. Mexican sunflower Tithonia spp.
Lantana Lantana spp.
Moth Vine Araujia sericifera syn. hortorum
Mother of Millions
Morning Glory Ipomoea learii syn. indica
Pampas Grass Cortaderia selloana
Pepper Tree Schinus areira
Privet Ligustrum lucidum
Singapore Daisy Sphagneticola trilobata
Umbrella Tree Schleffera actinphylla
Wandering Jew Tradescantia albiflora
Water Hyacinth Eichhornia crassipes
Watsonia Lily Watsonia spp.
Weeping Willow Salix spp.
Yellow allamanda Allamanda cathartica
Yellow bells Tecoma stans

Further information can be found at:
www.weeds.org.au
www.weeds.org.au/docs/jumping_the_garden_fence.pdf (1.6 MB)