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Diplotaxis tenuifolia
(L) DC. - Perennial Sand or Wall Rocket
[This Australian source does not
recognize the edible properties of this plant and views it solely as a
weed and pest. However, this and another species -
diplotaxis muralis (L) DC - along with Eruca
sativa, are known under the collective edible herb name Arrugula, Arugula,
Rocket, Roquette, Rucola, Rucoloa, Rughetta, and by other names.] ]
Weedy Significance
Origin: Southern & central Europe, Asia Minor.
Now spread to: Many warm-temperate climatic places with porous
calcareous soils
A weed of some importance: Throughout Europe (including UK), western
USA, Argentina, New Zealand, Australia
- Invades and dominates poor pastures
- Competes with hay crops making cutting difficult
- Confusion over value as fodder -- downside: not always readily
eaten by stock, if eaten it taints meat and dairy produce, &
unsubstantiated claims of poisoning stock
- If in cereal crops it is green at harvest and discolours, taints
and downgrades harvested grain
- Reduces benefits from summer fallows by depleting moisture and
nutrients
 World distribution:
Lincoln weed (Diplotaxis tenuifolia) (L.) DC is an
introduced perennial broadleaved herbaceous plant with a deep tap root
belonging to the family Brassicaceae (also known as Cruciferae). It
reproduces from seeds, annual crown regrowth and after cultivation,
from pieces of the root. Originating in southern and central Europe
and Asia Minor it has now spread to many warm-temperate climatic
places with porous calcareous soils. It is a weed of some importance
throughout Europe including the British Isles, western United States
of America, Argentina, New Zealand and Australia (16).
Australian distribution:
In Australia it is confined to southern areas occurring in both
coastal and inland areas of low to moderate rainfall with sandy often
calcareous, soils of neutral or high pH. Inland areas with colder
winters such as in northern, north- eastern South Australia and far
south western New South Wales receive more summer rainfall events,
important to this plant's predominantly summer growth.
States:
Conjecture on the present distribution of D. tenuifolia in
Australia has as much to do with the time and manner of its
introduction and spread, land management and transport systems and
changes in them as it has on climate and soil. The consequences
however are that the plant is legislated as noxious in Victoria and
South Australia. As its benefits as a pasture plant or pollen source
for bee hive maintenance in winter are considered outweighed by its
detrimental effects of tainting meat, dairy products and grain and
hay, invading and dominating poor pastures, depleting moisture and
nutrients in summer fallows and possibly poisoning livestock (16). On
the question of poisoning, many plants in the brassica (or crucifer)
family contain organic substances (glucosinolates) containing sulphur
and nitrogen. These fall into two groups: goitrogenic (goitre
inducing) and mustard oils. Mustard oils, ingested in excess, are
acutely fatal for livestock and humans. Brassica family members can
accumulate high levels of nitrates, also toxic if ingested in excess.
The levels of nitrates depend largely on the interplay of soil
nutrient, moisture, temperature and stage of growth variables. Leaving
aside the question of unpleasant but not toxic odours/tastes common in
the brassica family, those members described with substantial
poisonous status (11) did not include Diplotaxis.
 Early history:
- probably introduced between 1880 & 1900, possibly in ships
ballast as first found around Vic and SA ports including on known
ballast dumps
- Sown in SA as pasture on Eyre Peninsula until 1960s and to bind
sand dunes (failed) in NE pastoral country
Now occurs in Vic, SA, NSW, Tas & WA
- Vic: persists Bacchus Marsh, Geelong, Warrnambool areas -
roadsides, railway easements, some pastures
- SA: common on Eyre & Yorke Peninsulas, Upper North, Murray
Mallee, eastern slopes Mt Lofty and Barossa Ranges
- NSW: becoming well established in Broken Hill, Menindee,
Wentworth area, widely scattered but unimportant elsewhere
- WA & Tas: Isolated patches have not been allowed to develop into
problems
Noxious status:
- Victoria: declared noxious for whole state except Melbourne
metropolitan area
- South Australia: Class 3 Originally proclaimed a Schedule 3
plant under the Pest Plant Act 1975. Act repealed and replaced by
the Animal and Plant Control (Agricultural Protection and Other
Purposes) Act 1986. Now proclaimed under the 1986 Act in the plant
schedule as a Class 3 plant (specifically Class 3f) as:
Diplotaxis tenuifolia Lincoln weed
Photographer
: A. Danin
Control options:
The biology of D. tenuifolia restricts the range and ease of
its control, particularly now with very complex systems of Integrated
Weed Management (IWM) needed for the current diversity of cropping
systems and rotations. While strategic deep cultivation and follow up
measures on seedlings and rootlings can be effective on mature plants
(16) for a limited set of land class/land use combinations it is
inappropriate in most situations (non arable, native grasslands, low
or no till cropping systems etc). Selective hormone herbicides eg
MCPA,; 2,4DB; 2, 4-D formulations are mostly effective on seedling
stages (including 'rosettes' - see most labels) but require very
careful attention to the situation of use. It is essential to consider
other target species, host crop/pasture species, (especially legumes)
growth stage, soil and climatic conditions, etc and because of their
high volatility, proximity to sensitive off-target species -
especially grapevines, now so widespread into former broadacre
cropping areas.
With other effective herbicides; (eg chlorsulfuron, triasulfuron,
metsulfuron-methyl and other sulfonyl ureas) which have long half
lives on high pH soils, where D. tenuifolia tends to be, there
is a further risk of 'disintegrated' weed management as a result of
the extreme sensitivity of many pulse crops and pasture legumes or
another brassica (e.g. canola) as a following crop. Note that there is
no herbicide recommendation for Lincoln weed in pulse crops in SA (8).
All the issues of plants developing resistance to chemicals, plant
back periods etc covered in (4, 6) need to be carefully considered by
instructors in Integrated Weed Management Course presentations for
this weed. Furthermore the IWM situation analyses for specific groups
of land managers need to focus not only on D. tenuifolia but
also carefully examine the total suite of weeds to be controlled. A
particular product may be effective but not registered for D.
tenuifolia but is registered for that land use situation for
another weed present in the target suite. If passing safety checks for
the other risk factors a de facto herbicide application product may be
legitimised.
Lifecycle:
Perennial herbaceous plant with deep tap root reproducing from
seeds, crown and damaged root tissue. Dispersed mainly as seed
contaminating vehicles (e.g. rail) and carried on clothes, bags, in
water, mud etc. Some limited spread as root pieces on cultivation
equipment.
- seed germinates after autumn rain
- seedling becomes a slowly growing rosette through winter
- plant becomes reproductive in spring producing a bulk of upright
flower stems, leafy in the lower part
- plant grows most and flowers throughout summer into autumn while
developing a strong taproot
- seeds ripen in late summer and autumn
- topgrowth dies off in late autumn
- plant regrows annually (not as a rosette) in winter from crown
of deep stout often branched taproot and after rainfall, often
flowering all year
Habitat:
Warm-temperate regions, preferring
porous calcareous soils (Parsons and Cuthbertson 1992). It is a weed
of neglected areas, roadsides, railway easements and pastures (Parsons
and Cuthbertson 1992). Sand rocket invades dry coastal vegetation,
lowland grassland and grassy woodland, riparian vegetation and rock
outcrop vegetation (Carr
et al
1992).
Identification:
Another species of Diplotaxis, D. muralis (L.) DC
'Wall rocket' occurs in Australia. It is annual and sometimes
biennial, often found co-existing with D. tenuifolia and
extending into more extreme Mediterranean climates here and overseas
in Mediterranean areas and South Africa (13).
Essential differences for distinguishing D. muralis from
D. tenuifolia include;
- its round (3, 9, 10, 14, 17, 19) to oval cotyledons (14, 19)
- bristly hairs on lower parts of stems (3, 9, 10, 14, 17, 19)
- pale yellow flowers (3, 9, 14, 19)
- flattened/constricted pod (14, 17, 19) and
- its growth more prominent in spring-summer than in summer (17).
Other differences described by various authors are unreliable from
one location to another (particularly size measurements) and sometimes
inconsistent between authors eg;
- whether or not D. tenuifolia has rosette leaves (2, 19)
versus none (3, 10) or
- ascribing the foetid, foxy, or unpleasant odour of crushed
foliage to one species and omitting it from the other (12) whereas
it is a feature common to the whole Diplotaxis genus (5).
Mature plant:
Erect, 30-70cm up to 1m, leaves deeply lobed, apex pointed, `foxy'
odour, hairless stems, deep stout taproot with annual multi-stemmed
crown regrowth - not a rosette.
Photographer : A. Danin
Seeds:
Ovoid, brown or yellow-orange, slightly pitted, 1-1.5mm long.
Seedlings:
Cotyledons heart or kidney shaped;
First leaves oval, apex rounded, margin slightly serrated, hairless.
Immature plants:
Rosette of leaves increasingly deeply lobed, pointed apices,
unpleasant `foxy' smell when crushed.
Flowers:
Bright yellow four petalled flowers.
Fruit:
Seed pods cylindrical 1-2mm diameter, 3-5cm long, with many (50-80)
seeds in 2 rows separated by a longitudinal papery partition. Pod tip
cone shaped, seedless
Potential benefits of the weed:
- Fodder: high in crude protein, grows in summer when other
species decline
- Beekeeping: valued as a pollen source on Eyre Peninsula
References and further reading:
- Anon. (1986) Pest Plant Notes. Lincoln Weed (Diplotaxis
tenuifolia (L.) DC) (Pest Plants Commission, Adelaide). 2pp.
- Anon. (1987) APB Infonote 12/87. Lincoln Weed
(Agriculture Protection Board of WA). 2pp.
- Auld, B.A. and Medd, R.W. (1987)
Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press,
Melbourne). p.135.
- Bedgood, W. (2000). Weed
management. Tools for an integrated approach. (Department of Natural Resources and Environment
Agriculture Victorian, Horsham). 86pp.
- Black, J.M. (1948). Flora of South Australia. Part 2
(2nd
edn.). (Government Printer, Adelaide).pp.378-379.
- Britton, R. and Cummins, J. (1996). Weed management in a
cropping rotation. (Primary Industries South Australia - Rainbow
Press, Adelaide). p.27.
- Britton, R. and Fromm, G. (2000). Cereal Weed spraying Chart
2000. (Primary Industries South Australia).
- Britton, R. and Fromm,G. (2000). Pulse weed spraying chart
2000 (primary Industries South Australia).
- Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H.
(1992). Plants of Western New South Wales. (Inkata Press,
Melbourne). pp.322-323.
- Curtis, W.M. and Morris, D.I. (1993).
The student's flora of
Tasmania. Part 1 (2nd edn.). p.36.
- . Everist, S.L. (1981). Poisonous plants of Australia.
(2nd edn.). (Angus and Robertson, Sydney).pp.30, 209-217.
- Jessop, J.P. and Toelken, H.R. (eds)(1986).
Flora of South
Australia. Part 1. (Government Printer, Adelaide). pp. 391-392.
- Lazarides, M., Cowley, K. and Hohnen P. (1997). CSIRO
handbook of weeds. (CSIRO, Melbourne) p.64.
- Moerkerk, M.R. and Barnett, A.G. (1998).
More Crop Ceeds. (R.G.Richardson and F.J. Richardson, Melbourne). p.67.
- Parsons, J.M. (ed.).(1995). Australian weed control handbook
(10th edn.). (Inkata Press, Melbourne). 560pp.
- Parsons, W.T. and Cuthbertson, E.G. (1992).
Noxious weeds of
Australia. (Inkata Press,Melbourne). pp.338, 342-344.
- Prescott, A. (1994). It's blue with five petals. Wildflowers
of the Adelaide region. (Ann Prescott, Adelaide).pp.6-7.
- Richardson, R.G. and Shepherd, R.C.H. (eds.) (1992).
Recommendations for weed control in temperate Australia. Vols.1,
2a & 2b. (Weed Science Society of Victoria Inc., Melbourne).
- Wilding, J.L., Barnett, A.G. and Amor, R.L. (1998)
Crop Weeds (2nd edn.). (R.G. and F.J. Richardson, Melbourne). p.80.
Web Sites:
Updated:
17/10/2000 by Mihael Moerkerk
Sources:
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