Invasiveness Assessment - Heather (Calluna vulgaris) 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 Heather.

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: Heather
Scientific name: Calluna vulgaris

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	‘Seeds can germinate all year round but most successful germination occurs during spring and autumn.’ ‘Rarely germinate without exposure to light, and germination increases when seeds are heat treated’ (CRC for Australian Weed Management 2000) . Requires natural seasonal temperatures for germination.	MH	M
Establishment requirements?	‘It does not tolerate shade’ (CRC for Australian Weed Management 2003). Requires access to light and open spaces to establish.	ML	M
How much disturbance is required?	‘Grows on poor undeveloped grassland .. prefers frost flats, scrub and higher tussock grasslands.’ Colonises up to altitudes of 1,500 m and is thus a serious threat to Australia’s alpine country’ (CRC for Australian Weed Management 2003). Can establish in healthy and undisturbed natural ecosystems.	H	M
Growth/Competitive
Life form?	Evergreen perennial shrub (CRC for Australian Weed Management 2003). Life form– other	L	M
Allelopathic properties?	‘ releases allelopathic substances that may inhibit invasion and growth of some trees in heather-dominated heaths and moors’ (USDA Forest Service 2004).	MH	MH
Tolerates herb pressure?	‘Intense sheep grazing pressure .. will suppress new growth and flowering and may eventually eliminate C. vulgaris after a number of years. .. Light grazing will not be helpful’ (CRC for Australian Weed Management 2003). ‘Heather beetle Lochmaea suturalis .. was released in New Zealand in 1996 but has had limited success so far.’ ‘Heather production greatly exceeds heather consumption by herbivores' (USDA Forest Service 2004).	MH	MH
Normal growth rate?	Seedlings are easily out competed by grasses (CRC for Australian Weed Management 2003 ). ‘ .. slow growing, early successional shrub’ (USDA Forest Service 2004). Slow-growth, will be exceeded by many other species.	L	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	‘Extremely frost hardy and tolerates water logging’ (CRC for Australian Weed Management 2003). ‘Fire helps spread the plant’ (Weber 2003). Grows on fixed sand dunes. ‘Very tolerant of salt spray’ (Underhill 1971). Highly resistant to at least 2 and not susceptible to more than one.	H	MH
Reproduction
Reproductive system	Mainly reproduces by seed although vegetative reproduction occurs through layering. (CRC for Australian Weed Management 2003). Self-sterile but cross-pollinates (USDA Forest Service 2004).	H	MH
Number of propagules produced?	‘Each plant can produce several thousand flowers and tens of thousands of seeds’ (CRC for Australian Weed Management 2003). Above 2,000.	H	M
Propagule longevity?	‘.. seeds can remain viable for extended periods, up to 100 years’ (CRC for Australian Weed Management 2003).	H	M
Reproductive period?	‘Plants live for about 30 years’ (CRC for Australian Weed Management 2003). Produces viable propagules for 10 years or more.	H	M
Time to reproductive maturity?	‘In good conditions plants can produce seed within three years’ (CRC for Australian Weed Management 2003).	ML	M
Dispersal
Number of mechanisms?	‘ .. spread by wind, animals or walkers brushing against the plants’ (CRC for Australian Weed Management 2003). Small wind-dispersed seeds.	H	M
How far do they disperse?	‘It spreads at rates of up to seven kilometres a year along roads, through seeds being spread by road machinery ..’ (Department of Conservation n.d.). Very likely that some propagules will disperse greater than 1 km.	H	M

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