Invasiveness Assessment - Kochia (Bassia spp.) 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 Kochia.

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: Kochia
Scientific name: Bassia scoparia (syn. B. sieversiana, Kochia alata, K. scoparia var. culta, K. scoparia var. pubsecens, K. scoparia var. subvillosa, K. scoparia var. trichophila, K. sieversiana, K. trichophila)

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Will not flower and set seed if temperature is less than 15.5°C. ‘Most seed germinates in spring and early summer .. if conditions allow (late summer rains), seeds can also germinate from March to May’ (State Noxious Weed Control Board 1999). Does require seasonal disturbances for germination.	MH	MH
Establishment requirements?	‘Thrives in warm, low rainfall environments’ (CRC for Australian Weed Management 2003). ‘Competitiveness is limited under a closed canopy’ (Fisher et al 2000). Not documented as to whether or not the weed can establish under a canopy and prefers open, bare environments.	ML	H
How much disturbance is required?	‘In Colorado, was present in both logged forest and undisturbed, protected ponderosa-pine/Douglas fir forest’ (Wali 1999, cited in CIPC 2003). ‘Invades disturbed sites such as roadsides, railways and eroded banks, and also grows in crops, pastures and rangelands’ (CRC for Australian Weed Management 2003). Although thrives in highly disturbed natural ecosystems, can also establish in relatively intact or only minor disturbed natural ecosystem.	MH	MH
Growth/Competitive
Life form?	‘A bushy annual’ (CRC for Australian Weed Management 2003). Life form– other	L	M
Allelopathic properties?	‘Litter has allelopathic properties that affect crop plants and kochia seedlings. … Although it is allelopathic, the compounds appear to create autotoxicity that hastens its own demise’ (CIPC 2003). ‘Some degree of allelopathy’ (University of Connecticut 2004).	ML	MH
Tolerates herb pressure?	In Western Australia a control program where ‘high densities of sheep were used to provide extreme grazing pressure that caused defoliation of large plants and destruction of seedlings’ (CRC for Australian Weed Management 2003). Under moderate herbivory pressure, assume plant would be capable of seed production.	MH	M
Normal growth rate?	‘Grows rapidly through spring and summer.’ ‘Seedlings grow vigorously, out competing perennial species with their rapid growth’ (State Noxious Weed Control Board 1999). ‘Rapid coloniser in high light situations’ (CRC for Australian Weed Management 2003). Rapid growth that will equal competitive species of same life form.	MH	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Very drought tolerant. Tolerant to saline soils. ‘Seeds germinate in early spring because of frost tolerance’ (State Noxious Weed Control Board 1999). Waterlogging tolerant. Highly resistant to at least 2 and not susceptible to more than one.	H	MH
Reproduction
Reproductive system	Reproduces by seed only. Known to cross-pollinate but unknown whether it can self-pollinate (Csurhes & Edwards 1998).	ML	MH
Number of propagules produced?	‘Typically produces around 14,600 seeds per plant’ (State Noxious Weed Control Board 1999).	H	MH
Propagule longevity?	‘Laboratory studies report germination rates of 76 percent or better’. ‘Seeds buried in the soil have five percent viability after one year and zero percent after two years’ (State Noxious Weed Control Board 1999). ‘A small percentage of seeds may remain viable for two to four years’ (CRC for Australian Weed Management 2003).	L	MH
Reproductive period?	Annual plant. ‘Normally the time between germination and death is six to seven months’ (CRC for Australian Weed Management 2003).	L	M
Time to reproductive maturity?	Annual plant (CIPC 2003).	H	MH
Dispersal
Number of mechanisms?	Dispersed by wind and water (University of Connecticut 2004). Becomes a tumbleweed when mature (State Noxious Weed Control Board 1999).	MH	M
How far do they disperse?	When winds reach 25 miles per hour, stem breaks and plants tumble (State Noxious Weed Control Board 1999). ‘Can spread up to several kilometres in a single year [by tumbling]’ (CRC for Australian Weed Management 2003).	H	MH

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