Invasiveness Assessment - Italian lily (Arum italicum) in Victoria

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Italian lily.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
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Common Name: Italian lily
Scientific name: Arum italicum

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Seed germinates at much the same time as mature plants begin their growing season in autumn after being dormant over summer (Boyce 1993).	MH	MH
Establishment requirements?	Reported to be capable of invading dry coastal vegetation to riparian vegetation and pasture (Carr, Yugovic & Robinson 1992; Roy et al 1998). Therefore capable of establishing under a variety of light and moisture conditions.	MH	MH
How much disturbance is required?	Can invade riparian vegetation (Carr, Yugovic & Robinson 1992).	MH	MH
Growth/Competitive
Life form?	Tuberous geophyte (Carr, Yugovic & Robinson 1992).	ML	MH
Allelopathic properties?	There is no evidence of this.	L	M
Tolerates herb pressure?	All parts of the plant are poisonous; the juice is an irritant to the skin and mouth which causes arum species in general to be avoided by grazing species. Stock death has occurred after consuming arum species (Connor 1977; McBarron 1977; Shepherd 2004). Arums are troubled by a few insect pests including aphids, red spider mite and slugs and snails, severe damage only occurs under high infestation rates, therefore the plant is relatively untroubled by herbivore pressure. (Boyce 1993).	H	MH
Normal growth rate?	Anecdotal reports of the plant crowding out garden beds, however this doesn’t compare with species of the same life form, presumed to be similar (Dave’s Garden 2007).	M	ML
Stress tolerance to frost, drought, w/logg, sal. etc?	Drought tolerant, dies back during summer (Mendez & Obeso 1993) Frost tolerant; rated to zone 5a (-28.8°C) (Dave’s Garden 2007). Dieing back in summer would mean that it is unlikely to be effected by fire. Reported growing in a coastal dune system (Mendez & Obeso 1993). Therefore may have some tolerance to salinity. Unknown tolerance to waterlogging.	MH	MH
Reproduction
Reproductive system	Reproduces sexually with seed and vegetatively with tubers (Mendez & Obeso 1993).	H	H
Number of propagules produced?	Found to have an average seed production per inflorescence of 82.8 ± 62 with the maximum recorded as 335 (Albre, Quilichini & Gibernau 2003). Most plants produce 2-4 inflorescences which means the number of seeds produced is likely to be less than 1000 (Mendez & Diaz 2001).	ML	H
Propagule longevity?	Unknown.	M	L
Reproductive period?	Not exactly known, there are anecdotal reports of people trying to control self persisting populations for 18-30 years (Dave’s Garden 2007).	H	ML
Time to reproductive maturity?	On average it takes between 4 and 5 years for arums grown from seed to flower (Boyce 1993). Can produce independent daughter tubers in its second growing season (Mendez & Obeso 1993).	MH	H
Dispersal
Number of mechanisms?	Has red to orange berries which are dispersed by birds (Mendez & Obeso 1993)	H	H
How far do they disperse?	With the aid of bird dispersal seeds could travel more than 1 km, however dispersal distance for this species is not reported.	MH	M

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