Don looked at the Taiwan or Formosa lily, a beautiful tall lily that has escaped from gardens to become a weed. It is now outcompeting many of our native Australian plants, and degrading the value of our urban bushland.
Common name: Taiwan lily, Formosa lily Botanic name: Lilium formosanum
The species name formosanum is Latin, meaning ‘from Formosa’. The island of Formosa is now Taiwan.
Description: A bulbous plant with upright, straight, flowering stems 1-1.8m (up to 6′) tall in summer. Clusters of 1-3 lightly scented, trumpet-shaped flowers are borne at the top of each stem. The flowers are white with a pale yellow throat, and some have pink staining on the outside of the petals or when in the bud.
Problem areas: This plant has escaped from gardens and naturalised in southeast Australia from Queensland to Victoria and also on Lord Howe Island. It is usually found along roadside verges, drainage ditches, on wasteland and in bushland.
Reasons for success
The Taiwan lily grows from seed, bulbs and fleshy leaves (called bulb scales). The plant grows from seed to flowering stage in around 6-9 months (most lilies take two years from seed until flowering). Each flower produces hundreds of seeds. As the seeds mature, the seed pods are held upright and open slowly. Seeds are released over a 4-8 week period to take advantage of good conditions. Seeds are light and travel long distances on the wind. Even a single plant dumped in bushland can become the nucleus of a new weed infestation.
Hand weeding. This is the best option for home gardeners. Cut down the flowering stem before the plant sets seed. Remove the bulb, taking care not to leave any bulb scales in ground. You may have to remove some of the surrounding soil to catch small bulblets that break away from the parent plant.
Note: don’t just pull the plant up. The bulb is quite deep in the soil and all you’ll get is the stem with some roots (called stem roots).
The Taiwan lily is difficult to kill with glyphosate-based products (eg Roundup). The tops of treated plants will probably die down, but the bulbs will survive. A herbicide called Metsulfuron Methyl – sold as Brush Off – does work, but it is not readily available for home gardeners (try produce stores).
Do’s and Don’ts
Never plant potentially invasive exotic plants. Any plant that grows and spreads quickly in your garden is likely to do the same thing in the bush. It is also important not to dump garden refuse into the bushland.
Think about planting some of the lilies that are not weedy. Horticulturists at your local nursery will be able to recommend suitable species for your area. Here are some alternatives to get you started:
Alternatives to Taiwan lily Madonna lily (Lilium candidum) is not a weed, has pure white, fragrant flowers in summer and can be grown in the garden or in pots. Any of the white oriental liliums (Lilium Hybrids) are also an option. The November lily (Lilium longiflorum) grows to about 1m (3′) tall. It flowers in late spring to early summer (ie Nov-Dec) and does very well in pots. For white flowering, scented, shrubby plants also consider planting cutting-grown murrayas (Murraya paniculata) or gardenias (Gardenia spp.).
For information on weeds in your area contact your local council or bush regeneration group. Links to weed sites can be found at http://www.environment.gov.au/ (Environment Australia Online) and http://farrer.riv.csu.edu.au/ASGAP/index.html (The Association of Societies for Growing Australian Plants). The Society for Growing Australian Plants is now known as Australian Plants Society. There are branches in all areas. To contact your local group ring the head office on: (02) 9621 3437.