GARDEN THUGS CARESHEET FOR HOME GARDENERS IN WESTERN AUSTRALIA

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1 WEEDS OR WILDFLOWERS ENVIRONMENTAL WEEDS ACTION NETWORK (INC) GARDEN THUGS CARESHEET FOR HOME GARDENERS IN WESTERN AUSTRALIA One of the joys of gardening is to try one s hand at growing different plants and to see them flourish and reproduce themselves, providing a colourful and exotic landscape. Gardeners are also generous and love to give their excess plants away to family and friends or put them on community stalls and markets. The majority of Western Australia s environmental weeds have escaped from home gardens. These are known as garden escapees or Garden Thugs. Weeds dramatically alter essential habitats for our own unique flora and fauna. Garden refuse must now be chipped and composted after bulk collection by Councils, or binned and taken for deep burial. Regulations prohibit the dumping of excess garden plants and prunings in bushland. Despite this, some gardeners who have no idea that the plants will reproduce and have a devastating impact on our environment, still carry out this illegal practice. It has always been a joy to watch garden seedlings come up in the garden or even on verges and in bushland and think how clever those plants are to reproduce themselves. Today s gardeners must now come to realise that in Western Australia this ease of reproduction is a warning of the plants potential to turn into an environmental weed or Garden

2 Thug, and to escape into our already threatened bushland ecosystems. When not removed before seeding these plants become a very costly and time-consuming management problem for future taxpayers. Special care needs to be taken of both exotic and non-local native plant species when gardens are adjacent to bush reserves, parklands and waterways, to prevent their spread outside your garden walls. Also consider your neighbours when choosing plants that are vigorous climbers or suckering species. This Care Sheet endeavours to inform gardeners of best practices they can carry out to prevent Garden Thugs escaping into our bushland. DEFINITIONS (WONS) Weeds of National Significance (DP) are Declared Plants in all or parts of Western Australia and FERNS Ferns reproduce mainly from spores, stolons or rhizomes. Particular care must be taken as they spread readily when gardens are adjacent to creek-lines and moist areas especially in the higher rainfall areas of our State. Garden Thugs include soft tree fern or Cyathea cooperii, batwing fern or Histiopteris incisa, holly fern, and fishbone fern. v Spore bearing fronds need to be removed before the spores are ripe. v Leftover pieces of rhizome and roots from plant divisions should be placed in plastic bags and disposed in your Council rubbish bin for deep burial. v Solarisation in black plastic for several weeks during the summer heat can also be very effective. (PP) are Pest Plants declared by local councils. 2 WEEDS OR WILDFLOWERS

3 BULBS, CORMS AND RHIZOMES Bulbs, corms and rhizomes are a popular addition to today s gardens. Careful selection is required, as they can be a threat to our bushland. Many of these plants have the ability to spread rapidly amongst our native species and make eradication and control very difficult. As well, many are highly toxic. The most troublesome Garden Thugs include many South African bulbs such as freesias, lachenalias or soldiers, jonquils, small flowering gladiolus, sparaxis, ixias, babianas, watsonia (PP), dietes or moraea, and crocosmia. Others are oxalis, chincherinchee and some alliums from the onion family. Plants with rhizomes such as arum lily (DP), cannas and taro cause infestations in our wetlands and streams. v Seed heads should be removed before they mature. v All surplus bulbs, corms and pieces of root rhizomes placed in plastic bags and disposed of carefully to deep burial. WATER PLANTS Water features are a popular item in home gardens. Special care must be taken to purchase plants from reliable suppliers. Water plants as Garden Thugs can have a devastating effect in our wetlands and waterways. Water plants that have escaped the garden pond are water hyacinth (DP), salvinia (WONS, DP), water lettuce (DP), bull rushes, papyrus grass, azolla, calocasia (taro), elephant s ears, arum lily (DP), parrots feather (DP), ribbon weed (DP), vallisneria, sagittaria and hydrocotyle (DP). v Careful disposal in plastic bags of any excess water plants is very important. v Dispose of exotic fish and water snails in the same way to prevent escape into rivers and streams. v For some free-floating aquatic weeds like salvinia and water hyacinth which are illegal, seek advice from the Department of Agriculture WILDFLOWERS OR WEEDS 3

4 COTTAGE PLANTS AND HERBS Many colourful annuals and perennial plants and herbs make up the cottage garden. Unfortunately over the years many of these plants have become well established Garden Thugs. Cottage Garden Thugs include Italian and French lavender, species of verbascum, oenothera or evening primrose, salvia, verbena, euphorbia or spurges, leonotus or lions tails pelargoniums, alstroemeria, agapanthus, hypericum or St John s wort, culinary herbs such as mint, basil, fennel and New Zealand spinach. Some newer introductions making their presence felt are gaura or white butterflies, arctotus, gazania, and oestospermum or African daisies. Annual or short lived perennial species such as statice, echium or Paterson s curse (DP), scabiosa, alyssum, forget-me-nots, heliotrope, Californian and red field poppies, senecio daisies, sunflowers, and swan plant (DP) have all become naturalised. Precautions to take v Careful plant selection, good garden maintenance, correct disposal of seed-heads, prunings and surplus root rhizomes will help prevent further spread. v Gardeners should be very conscious of the ease of spread of such plants within their garden and if too vigorous and spreading remove them altogether with careful disposal in plastic bags and bin. v Avoid easy to grow cottage plants from markets and stall, these are usually already well known Garden Thugs. 4 WEEDS OR WILDFLOWERS

5 CLIMBERS AND CREEPERS Climbers and creepers as Garden Thugs smother large areas and have the ability to overwhelm and eventually destroy whole habitats. Amongst the worst are asparagus species like bridal creeper (WONS), rubber vine (WONS, DP), ivies, morning glory, vinca, lippia or phylla, mad myrtle, yellow allamanda, honeysuckle, pea flowered lathyrus and dolichos, nasturtium, blackberry (WONS, DP), briar rose species, passionfruit, balloon creepers and feral grape vines, all have garden origins. Precautions to take v Keep these plants well contained in the role they were intended to play within your landscaping. v Some sucker extensively and others may form new plants where the long growing tip hits the ground. v Keep seed heads trimmed and remove unused fruits before they mature. v Dispose of prunings etc correctly by local council deep burial. GRASSES, SEDGES AND STRAPPY PLANTS Modern trends in landscaping have broadened the interest in these types of plants. Annual and perennial grasses are some of our worst Garden Thugs. They form a large part of our wild landscapes today, to the exclusion of our native species. Notable Garden Thugs are pampas grass, bull rushes, foxtail grass, blowfly grasses, couch, kikuyu, buffalo, miscanthus, phoenix palms, arundo and fountain grass. Species of dietes or morea and agapanthus from South Africa set huge amounts of seed and are showing signs of naturalising. Precautions to take v The removal of seed heads before they are ripe prevents them being carried by birds or dispersed by the wind. v This is essential best practice gardening. v Place excess runners in a plastic bag before placing in the rubbish bin for deep burial. v Look for local species to plant. WILDFLOWERS OR WEEDS 5

6 SHRUBS AND TREES Many of our commonly grown woody garden shrubs and trees have become Garden Thugs. They spread by seed or berry dispersal, suckering, or careless disposal of prunings, sometimes indiscriminately dumped in out of the way places in bush reserves. Notable garden escapes are species of tree lucerne or tagasaste, tamarisk, schinus or Brazilian pepper, tree of heaven (PP), tecoma, oleander, willow, poplar, cotoneaster, pyracantha, genista or yellow broom, lantana (WONS), polygala, podalyria, pine, blue broom, datura (DP), coral tree, camphor laurel, and buddleia. Fruiting Garden Thugs are olives, bananas, loquats, seedling plums and apples. v Careful plant selection and garden maintenance and the correct disposal of all prunings will help prevent further spread. CACTI AND SUCCULENTS Many cacti and succulents from a bygone era have readily settled into bushland areas as Garden Thugs. Revived interest in these architectural plants could see a renewed spread. Current cacti and succulent Garden Thugs are prickly pear (DP), numerous types of pig face or carpobrutus, lampranthus, mesembyanthemum, drosanthemum. Others are tetragonia, agave (century plant) and yucca. v Cacti and succulents can reproduce by seed but usually spread from dumped pieces of leaves and stems that form new plants. v Careful disposal of seed heads, stems and leaves by deep burial are essential. v Plan your pruning programme to prevent seed heads, berries and fruit becoming fully matured and ready to be dispersed. 6 WEEDS OR WILDFLOWERS

7 AUSTRALIAN NATIVES Native plants from Western Australian and from other states of Australia, grown away from their natural habitat, have become important Garden Thugs in Western Australia. Victorian tea tree or Leptospermum laevigatum (PP) brought to Western Australia to form wind breaks in a bygone hedging era, has spread dramatically and continues to spread throughout southern Western Australia. Other introduced Australian species include the wattles or acacias such as the Cootamundra, silver, cedar, Sydney golden, Queensland silver, Australia s golden floral emblem, Flinders Range, and Mt Morgan wattles, all of which are prolific seeders. Many well know Eucalyptus are Garden Thugs such as lemon scented gum, sugar gum, blue gum, spotted gum, bangalay and sweet pittosporum. These trees change the appearance of our natural landscape and degrade our environment. Also of concern in local Perth reserves are escaped Western Australian Geraldton wax, hibbertia and calothamnus species, and other eucalypts such as river gum and Bald Island marlock, and agonis or peppermint trees. Kunzea baxteri has naturalised away from its own local area in the southwest. v Plan to carry out your pruning programme after flowering and before seed heads are mature. v Dispose of prunings in the recommended way. v Remove any naturalised seedlings that appear. v Careful plant choice is required especially in areas close to parks and bush reserves. v Many local councils, Friends of bush care groups and Wildflower Society branches have lists of plants local to your area and information on how to grow them and could probably advise on what species not to plant in your area. WILDFLOWERS OR WEEDS 7

8 NEW INTRODUCTIONS The behaviour of many new plants introduced through your local garden centre has not been monitored to gauge their ability to naturalise under Western Australian conditions. Gardeners have an important role to play here by observing these plants and by reporting any trend they may have to naturalise and become Garden Thugs to the local bushcare group, CALM Wildlife and Agriculture Western Australia. Gardeners can play a valuable role in preventing further garden escapes into our unique bushlands. Compiled by Hazel Dempster, April 2004 Environmental Weeds Action Network (Inc) (EWAN) PO Box 380, Greenwood WA ewan@iinet.net.au HOW CAN YOU HELP? v Avoid growing weedy plants and Garden Thugs. v Practise responsible garden maintenance and disposal. v Keep your plants within the garden boundary. v Remove any escapes from the surrounding area. v Report any weedy habits of new plants. v Local councils control any Garden Thugs that may appear in their disposal sites. v Campaign against dumping in your area v Get to know the needs of your local parks and bushland. Western Weeds: A guide to the weeds of Western Australia Authors: BMJ Hussey, GJ Keighery, RD Cousens, J Dodd, SG Lloyd Publisher: The Plant Protection Society of Western Australia (Inc) 1997 Further Reading Bushland Weeds: A practical guide to their management. Authors: Kate Brown, Kris Brooks, illustrated by L Sandiford Publisher: Environmental Weeds Action Network (Inc) WEEDS OR WILDFLOWERS