Carthamus is from the medieval Latin name qartum or the Arabic quarthami which is the name for Safflower and means to paint, referring to the dyes extracted from the flowers of some species.
Lanatus, a Latin word, means woolly referring to the woolly haired leaves and stems of some forms of the plant.
Saffron Thistle - Saffron is derived from Safflower. Thistle is of uncertain origin but may be derived from the Germanic thisilatz.
Other Names:
Other names:
Barnaby Thistle
Chinese Thistle
Common Star Thistle
Distaff
False Star Thistle
Saffron Star Thistle
Star Thistle
Sulphur Thistle
Woolly Kentrophyllum
Woolly Safflower
Woolly Star Thistle
Yellow Chinese Thistle.
Summary
Saffron Thistle is a yellow to cream flowered, spiny, slightly hairy to woolly, annual thistle that flowers in spring and summer and grows to around 1 metre tall with a much branched flowering stem with leaf like, spiny flower bracts and seeds that look like shuttlecocks. The leaves are rigid and prominently veined, have cobweb-like hairs, are spine-tipped and the margins are spiny-toothed. The stems of are not winged nor spiny and bear a single flower head. The seeds are topped by slender scales.
It is native to Europe and a weed of crops, pasture and waste ground and is a declared weed.
Description
Cotyledons:
Two. Oval about 50 mm long. Tip rounded. Sides convex. Base tapered. Surface hairless. Petiole 5-10 mm long and shorter than the blade. The seedling has a very short hypocotyl and no epicotyl.
First leaves:
Appear to be paired. Oval. 70-100 mm long. Stalked. Soft. Tips lightly pointed. Edges scalloped with a few weak spines. Hairless. Glossy green.
Leaves:
Rosette Leaves
Blade - 100-250 mm long. Rigid. Olive to bright green. Leathery. More or less woolly. Usually recurved. Deeply lobed with scalloped edges and a broad terminal lobe. Each lobe ends in a short spine. 5-7 Veins obvious from below. Spiny edges. Base tapered. Prominent veins.
Petiole - Short.
Stem leaves.
Alternate.
Blade - Short spines on tip and lobes. Triangular. Up to 150 x 30 mm long. Usually 20-80mm x 15-35mm. Curved back, slightly downwards and away from the stem. Very stiff. Clasp the stem. 5-7 Veins obvious from below. Hairless or a few cobweb hairs and some plants downy on the upper surface.
Petiole - None.
Stems:
Flower stem - Erect. 200-2000 mm (usually around 1000 mm in agricultural infestations). Pale green, brown, yellowish or white. Sparse crisp to woolly and tiny glandular hairs. Elongate in spring. Stiff. Round and fluted with lengthwise grooves and no wings. Solid with a pithy core. Hairless or a few fine hairs, but some plants may be downy. Upper branches are often more hairy than lower ones. Unbranched near the base but branched (often profusely) near the top.
Flower head:
20-25 mm long. Egg shaped and attached at the broad end. Stalkless. Webby hairy near base. Single at the ends of corymbose upper branches. Outer and intermediate bracts with pale hard bases. Innermost bracts papery near tips with small spines on either side of a longer terminal spine. Bracts leaf like, spiny and hairy.
Flowers:
Yellow, cream or rarely white with faint red or black veins. About 40 mm wide. Strong, spiny, stiff, lance shaped bracts at the base of the flower.
Ovary -
Perianth -
Stamens -
Anthers - Tailed at the base.
Fruit:
Achene (cypsela) that looks like a shuttlecock. 6 mm long. Brown to greyish. 4 ribbed and sometimes wrinkled or pitted near the top. The 4 angled base is about 3 mm long and surmounted by a fringe of semi transparent scales.
Seeds:
Grey brown, 4 angled, egg to wedge shaped, smooth 3-6 mm long. Some have a pappus of several rows of stiff bristles of uneven lengths up to 10 mm long.
Roots:
Taproot.
Key Characters:
Yellow flowers. Outer flower head bracts longer than the inner ones and similar to leaves with spines. Seeds obliquely attached to the receptacle. Outer florets ligulate, centre ones tubular with many fine straight hairs between the florets. Anthers tailed at the base.
Biology
Life cycle:
Annual or rarely biennial. The major germination occurs in autumn after the first rains with minor ones up to October. The seedling develops into a rosette and the flowering stem emerges in late September to October. The rosette leaves tend to die off as the stem elongates. At this time the spines become more rigid and repel stock. Flowers are formed in early summer (November/December) and may continue for some months if moisture is available. Seeds ripen in December/January and usually remain in the flower head until the bracts dry out and bend back to expose them. Disturbance by stock or wind may shake some seed loose before the bracts dry. Most plants die with onset of summer drought with rare individuals surviving for a second season under moist conditions.
Physiology:
The seed has a high feed value and readily eaten by animals.
Flowering stems will grow 7-15 mm per day.
Reproduction:
Pollinated by bees.
Requires a cold winter period to initiate flowering.
Less than 10 to more than 40 flower heads may be produced per plant with 8-16 seeds per head. Seed production varies from 70 to 255 viable seeds per plant.
Flowering times:
November to March. In WA the major flowering occurs in November whereas the major flowering in eastern Australia is February-March.
Seed Biology and Germination:
About 60% of the viable seeds produced have a pappus of stiff hairs.
Seed is heavy compared to other annual thistles and ranges from 12-26 mg/seed (Michael, 1968).
10-20% of seeds close to the soil surface germinate in the next season. A further 30% germinate in the next season and very few after that. Less than 5% of seeds germinate when buried 50 mm deep. One third of the seed buried 100-150 mm deep can be viable 10 years after burial. However, in the field, termites often attack the seed so none is detected after 8 years of burial. Seed dormancy varies depending on the area the seed is collected from and the site at which it is grown. (Quinlivan, 1965; Quinlivan and Peirce, 1968; Peirce and Quinlivan, 1971; Peirce, 1990).
The optimum temperature for germination is 10/200C (Groves and Kaye, 1989).
It takes most seed at least 6 months before it reaches its maximum germination potential.
Washing the seed with water increases the amount of seed that will germinate by leaching a water soluble inhibitor, which is probably abscisic acid. Leaching in the presence of red light during imbibition breaks seed dormancy (Wright et al, 1980)
Seed dormancy is reduced by exposing the seed to high alternating temperatures. This may explain why dormancy is higher in seed that is retained in the head over summer compared to those that are shed.
Saffron Thistle is one of the most sensitive species to moisture stress for the initiation of germination but was the most tolerant of stress once germination had commenced Groves and Kaye, 1989).
Hybrids:
C. lanatus is a complex with 2 subspecies (lanatus and baeticus) resulting from crosses with other Carthamus species. They are distinguished by the length of their spiny, outer flower bracts. C. lanatus has outer bracts 1.5 times the length of the inner whereas in C. baeticus they are twice as long. A range of hybrids, with intermediate morphological characters, usually appear where there is contact between the subspecies and other Carthamus species. The hybrids are generally less fertile or sterile.
Population Dynamics and Dispersal:
Dispersal is entirely by seed. Most pappus bearing seeds and many others are shed at early maturity close to the plant. They are not spread by wind but the pappus does allow the seed to float. The stiff pappus helps the seed adhere to fur, wool clothing and bags and allows it to float for transport in water. The spiny flower head tangles in fur and wool dispersing seed as the animal moves or when the wool and hides are shipped. The whole plant breaks of at the base and tumbles, effectively distributing seed over medium distances. Long range transport of seed is by movement of contaminated grain and produce including wool, stock movement (mainly sheep), on peoples clothing and by seeds lodged in mud on vehicles. It doesn't pass through animals in a viable condition.
Where the density of Saffron Thistle is greater than 20 plants /m2 in clover and grass pasture seedling mortality can approach 40%. In sparser pastures this fell to 18%.
Heavy grazing, generally results in increased infestations of Saffron Thistle because stock usually have a preference for companion species. It doesn't invade perennial pastures. In legume based pastures increasing phosphate fertilisation usually decreases the level of infestation. Where the legume content is low, increasing phosphate applications usually results in greater infestations.
Infestation levels vary considerably between seasons. They tend to be dense in low rainfall years and sparser in high rainfall seasons.
Origin and History:
Mediterranean and Western Asia.
Probably introduced into SA around 1860, and spread around Australia as a contaminant of fodder and grain in the late 1800's. It was introduced to New Zealand and probably Western Australia, as a contaminant of wheat.
Distribution:
ACT, NSW, Southern NT, Southern QLD, SA, VIC, Southern WA and small areas on pastoral land in Tasmania. It is most troublesome in the drier cereal growing areas.
It occurs in most temperate areas of the world but is only regarded as a weed in Australia. In Western Australia it infests over 400,000 ha. It is the most widely distributed of the Carthamus species
Habitats:
Climate:
Warm temperate and subtropical semi arid regions.
It is a serious weed in areas with an annual rainfall of 500 to 850 mm in eastern Australia and in areas down to 300 mm in Western Australia.
It is very cold tolerant.
The density varies much between seasons.
Soil:
Under high fertility conditions other plants tend to displace Saffron Thistle, so it is more abundant on the less fertile soils.
It has no particular affinity for soil types, but tends to be less common on the sands and in WA is most abundant on the red clays. It is most common on disturbed loamy and clayey soils in NSW, and generally prefers cultivated or disturbed soils elsewhere.
Plant Associations:
It tends to be a weed of cultivation and disturbed sites although it does occur in pastoral areas especially where it is overgrazed or suffering drought.
Significance:
Beneficial:
Poor fodder. Honey.
Folk medicine for promoting perspiration, curing fever and destroying intestinal parasites.
Provides ground cover and reduces erosion on low fertile soils or in drought conditions.
Seed has about the same crude protein content as wheat but a lower digestibility of 26.3%. Free range turkeys have been fattened on Saffron Thistle stands. Seed can be a useful stock feed source in drought years.
Strong taproot opens the soil to allow water and air to enter.
It is a potential gene source for leaf spot and bacterial blight resistance for transfer to Safflower.
Cultivated in tropical Africa for its oil for paint manufacture and colouring. A good quality, semi drying oil, similar to linseed oil, can be extracted from the seed and the remaining meal used as a stock feed.
Detrimental:
Weed of crops causing yield loss and grain contamination. Difficult to mechanically remove from cereal grains. Green material at harvest can cause blockages of harvesters.
Weed of pastures causing loss of grazing in infested areas.
Weed of roadsides.
Contaminates wool with vegetable matter. Saffron is the most common thistle seed in wool, but it is easily removed. Spiny bracts, leaves and flower heads cause discomfort to shearers and sheep handlers.
Competes for moisture, light and nutrients.
Little grazing value.
Restricts pasture growth in low fertility soils.
Restricts livestock movement in late spring and summer.
Causes difficulty in mustering and hinders working dogs, horses and vehicles.
Causes eye and mouth injuries in stock.
Reduces grain yields by up to 70%.
Decreases property values.
Estimated losses in SA, Vic and NSW were $3.5M per year in 1997 (based on Sloan et al, 1988).
Host for the cotton disease Verticillium dahliae.
Host for the root rotting disease of Safflower Phytophthora drechsleri.
Produce containing Saffron seed can not be sold where it is a declared weed.
Saffron Thistle seed in wheat discolours flour and may damage milling equipment.
Dried stems left after slashing can puncture tyres.
The spiny leaves and bracts can transmit virus diseases of grazing animals.
Toxicity:
Not recorded as toxic.
Legislation:
Declared plant in NSW, QLD, TAS, VIC and WA, . It was declared in SA from 1890 until 1990 but revoked because of the widespread distribution.
It was first declared under the Thistle act in Victoria in 1892.
Management and Control:
The rosettes are often grazed until the spiny erect growth emerges. Animals will work their way into infestations as other feed becomes scarce.
2,4-D and MCPA have been used for many years and are most effective on plants up to budding. At rates required for high levels of control they usually cause some damage to clovers and medics but are safe in tillering wheat and barley crops. 2,4-D amine is the most cost effective of the hormone herbicides for Saffron Thistle control.
"Spray Grazing" is effective. In this technique a low rates of hormone herbicide such as 2,4-D amine (750 mL/ha) or MCPA (1 L/ha) is applied just before the flowering stem elongates in September and then 4-5 times the normal stocking rate of sheep is applied 7 days after spraying.
Lontrel (Clopyralid) has provided the most reliable control in cereal crops. It is often mixed with hormone herbicides to control a wider range of weeds.
Preventing seed set or "Spray Topping" is another reliable control technique for pastures. The preferred mixture is glyphosate (450 g/L) at 400 mL/ha plus 2,4-D ester (800 g/L) at 400 mL/ha applied at early flowering. This provides good control with little regrowth if the plants are not moisture stressed. Paraquat(200 g/L) applied at 500-1000 mL/ha plus 1% oil when the thistle is in the stem elongation stage until the first flowers are opening is also effective (Fromm 1990). Spray.Seed at 1L/ha provides similar control. In some years plants recover after the Paraquat and Spray.Seed treatments or glyphosate alone and set new viable seed. Because Saffron Thistle flowers somewhat later than pasture species the herbicide treatments cause little damage. Boom sprays need to raised so there is a double overlap of spray at the height of the flowers.
Tordon 75-D is useful for fence lines and unused areas because it contains a soil residual herbicide that controls plants emerging after spraying.
Increasing pasture competition with fertilisers, pest control, better suited species and better grazing management to avoid overgrazing will reduce the impact of Saffron Thistle. In one experiment in NSW, Saffron Thistle was reduced by 90% by applying super to improved pasture species.
Mowing or preferably slashing is effective providing it is done before flowering and repeated as necessary.
Grazing with sheep and cattle usually increases the density of Saffron Thistle.
Long term grazing with goats can reduce infestations. In WA it took 3 years before levels started to drop. After 5 years levels had fallen from 30 plants/m2 to 1 plant/m2.
Grazing with horses or goats can help contain a small infestation. Pre treatment with 2,4-D improves the palatability.
In the first summer after growth it is somewhat resistant to burning, but it usually burns well in the next summer.
Thresholds:
1 plant/m2 can cause contamination of grain. 10-20 plants/m2 will reduce grain yields by about 10% or more.
More than 5 plants/m2 restricts stock from grazing infested areas.
Eradication strategies:
Eradication will be difficult if not impossible and take many years. The following is a best bet set of options.
Plan on going into a continuous crop rotation for 5-8 years.
Apply 500 mL/ha glyphosate(450g/L) the bud stage (late October). 2 weeks later apply 500 mL/ha paraquat(250g/L) plus 1% oil (i.e. 1 L spraying oil per 100 L of spray mix).
Graze with goats over summer to eat escaping flower heads.
Burn in summer to expose seed to high alternating temperatures which helps break dormancy. (Herbicide applications in spring will make the thistle more susceptible to fire).
Shallow cultivate (10 mm deep) 5 days after the first rains to kill germinating seed and bury others so they will germinate.
Apply 750 mL/ha glyphosate(450g/L) plus 500 mL/ha Tordon 75-D plus 1% wetting agent 7 days after the second rain. (the extra wetting agent gives greater germination of surface seed). 7 days after the third rain, plough to 100 mm or more deep to bury seed too deep to emerge. Plant a short season wheat with a minimum tillage seeder to avoid disturbing buried thistle seed. Increase the seeding rate by 30% to increase crop competition with the weeds.
Apply 500 mL/ha paraquat(250g/L) plus 1% oil just before the crop emerges.
If more than 20 thistles /m2 emerge, spray the crop at the 2 leaf stage with 300 mL/ha Lontrel. Otherwise, wait until the 6 leaf stage of the crop and spray with 200 mL/ha Lontrel plus 500 mL/ha of Tordon 75-D.
Check the crop at the elongation stage and if thistles are found respray with 250 mL/ha of Lontrel plus 1000 mL/ha 2,4-D amine(500g/L).
Use a seed catcher behind the harvester to collect weed seed. Treat with diesel, burn or dump it where it can't reinfest the paddock.
Graze with goats after harvest.
Burn stubble.
In the second season, shallow cultivate, 5 days after the first rain. Apply 750 mL/ha of glyphosate(450g/L) plus 250 mL/ha dicamba(200g/L) 7 days after the second rain and plant barley with a minimum tillage seeder. Use a higher seeding rate. If more than 20 Saffron Thistle per square metre, apply 300 mL/ha Lontrel. If less, apply Lontrel at the 6 leaf stage of the crop (Don't use Tordon because this may carry through to next years crop). For the rest of the season treat as for wheat above.
In the third season, shallow cultivate after the first rain.
5 days after the second rain, apply 500mL/ha of glyphosate(450g/L) plus 250 mL/ha of Dicamba(200g/L) plus 1 kg/ha of Atrazine(900g/kg) granules plus 1% oil plus 1 kg of crystalline ammonium sulphate per 100 L of spray mix.
Plant triazine tolerant canola a day or two later. Extra nitrogenous fertiliser will be required to improve crop competition and make up for the run down over the previous two cereal crops. Avoid using insecticides detrimental to ants such as Talstar and endosulfan, because the ants are probably helping to reduce the dormant seed bank.
At the 3-4 leaf stage of the crop, apply 1 kg/ha of atrazine(900g/kg) granules plus 300 mL/ha Lontrel plus 1% oil.
Check the crop at stem elongation and if thistles are found apply 300 mL/ha of clopyralid(300g/L) or Lontrel.
Swath the crop or desiccate with 2-3 L/ha of paraquat(250g/L) or Reglone. This will also control any late emerging thistles.
Graze with goats after harvest.
In the fourth season a legume is required to replenish soil nitrogen.
Shallow cultivate after the first rain
Apply 500 mL/ha glyphosate(450g/L) plus 100 mL/ha Goal CT.
Apply 1 L/ha Simazine(500g/L) plus 2 L/ha Diuron(500g/L) immediately before planting Lupins, Faba Beans or Chickpeas. Use 3L/ha Diuron(500g/L) if planting peas. Use short season varieties so that the crop has finished pod fill before the thistle flowers.
Apply 1 L/ha paraquat(250g/L) plus 1% oil when the crop seeds have reached full size and the Saffron Thistle is budding to just starting to flower. Repeat after harvest if necessary.
Graze after harvest with goats.
Alternatively use a green manure crop for the fourth season, These have shown potential in the Saffron Thistle areas. Plant the legume species that will provide the greatest bulk for your district, then shallow plough it in spring to kill it and conserve moisture for the following cereal.
Repeat the 4 year program above.
Talk to your local agronomist about the best crop rotations for your area and modify the above accordingly.
In paddocks that can't be cropped, a combination of the following is useful.
1) planting and encouraging pasture legumes then fertilising with superphosphate.
2) goat grazing over spring and summer plus
3) 'spray grazing' (750-1000 mL/ha of 2,4-D amine(500g/L) applied in winter when the thistle is in the rosette stage followed 7 days later with 4-5 times the normal stocking rate of wethers) plus
4) 400 mL/ha glyphosate (450 g/L) plus 400 mL/ha 2,4-D amine at the budding to early flowering stage of the Saffron Thistle and
5) using goats for grazing will reduce Saffron Thistle to low levels over a number of years. In higher rainfall areas, establishing perennial pasture species will reduce Saffron Thistle to insignificant levels.
On fence lines, roadsides and other unused areas, use an annual application of 2 L/ha of Tordon 75-D at the beginning of stem elongation (late September) plus a follow up spray of 1 L/ha of paraquat(250g/L) if required in early summer. This will not kill most grasses which helps prevent reinfestation. Bromacil may also be used in industrial situations where there are no trees close by and no run off from the site.
Prevent reinfestation.
Shear all sheep that have been exposed to saffron seed before moving them into clean paddocks.
Don't buy feed or seed from infested farms. Your thistle problem most probably arose from contaminated seed or produce purchased many years ago.
Watch creek lines and flood ways. Saffron Thistle seed will float and this is a potential source of external infestation.
Remove odd plants and spray the area and a 3 metre buffer strip, until it is just wet, with a mixture of 1 litre of Tordon 75-D in 100 litres of water.
Herbicide resistance:
No resistance recorded.
Biological Control:
Because Saffron Thistle is closely related to the commercial Safflower, biological control is not likely to be implemented.
Native budworm (Helicoverpa species)occasionally causes damage to the flowering heads.
Seeds are eaten by termites in some districts.
Red legged earth mite cause severe damage in some years.
Related plants:
Glaucous Star Thistle(Carthamus leucocaulos or C. glaucus)
Safflower(Carthamus tinctorius)
Toothed Thistle (Carthamus dentatus).
Plants of similar appearance:
Spear Thistle (Cirsium vulgare) and Sheep and Slender Thistles (Carduus species) like most other thistles have pink or purple flowers.
Cultivated Safflower (Carthamus tinctorius L.) has undivided leaves and darker yellow flowers.
St Barnaby's Thistle (Centaurea solstitialis) and Maltese Cockspur (Centaurea melitensis)have yellow flowers but the heads are much smaller and rounder than Saffron Thistle and they don't have lobed and spined leaves. Golden Thistle (Scolymus hispanicus) has flowers that are very similar to Saffron Thistle but the "petals" are broader and the seeds are flat. Spotted Thistle (Scolymus maculatus) also has yellow flowers but only occurs in NSW and QLD.
Toothed Thistle (Carthamus dentatus) has pink/purple flowers and only occurs in central NSW and Vic.
Glaucous Star Thistle(Carthamus leucocaulos or glaucus) has purplish flowers and is rare in VIC, SA and WA.
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P89. Photos.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P937. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P395. Diagram P397.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P721-722. Photo.
Fromm, G.M. (1990). Chemical control of Saffron Thistle (Carthamus lanatus L.) in pasture in the South Australia Mallee. Plant Protection Quarterly, 5(1),14-17.
Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P47. Photos.
Groves, R.H. and Kaye, P.E. 1989. Germination and phenology of seven introduced thistle species in southern Australia. Australian Journal of Botany 28:193-8.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P32-33. Diagrams.
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #260.2.
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P666.
Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P160-162. Photo. Diagrams.
Michael, P.W. (1968). Thistles in south eastern Australia - some ecological and economic considerations. Proceedings of the First Victorian Weeds Conference 4,12-16.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P194-197 (photo).
Peirce, J.R. (1990). Morphological and phenological variation in three populations of saffron thistle Carthamus lanatus L. from Western Australia. Australian Journal of Agricultural Research 41, 1193-201.
Peirce, J.R. (1995). Carthamus lanatus L. in The biology of Australian Weeds, Ed. R.H. Groves, R.C.H. Shepherd and R.G. Richardson, Volume 1, pp.51-66. (R.G. and F.J. Richardson, Frankston, Australia).
Peirce, J.R. and Quinlivan, B.J. (1971). Factors controlling seed dormancy in Saffron Thistle (Carthamus lanatus). Proceedings of the Australian Seed Research Conference, Mount Gambier, South Australia. 1(6), 15-18.
Quinlivan, B.J. (1965). Seed dormancy in saffron thistle. Proceedings of the Australian Weeds Conference, Toowoomba, Queensland 1,1(a),pp.2-3.
Quinlivan, B.J. and Peirce, J.R. (1968). The long term field germination of saffron thistle, Carthamus lanatus L. and the life span of dormant seeds in the Geraldton region of Western Australia. Journal of the Australian Institute of Agricultural Science 34, 231-2.
Sloan, Cooke and King. 1988. The economic impact of pasture weeds, pests and diseases on the Australian wool industry. (Sloan, Cooke and King Pty Ltd, Sydney). P23-5.
Wright, G.C., McWilliam, J.R. and Whalley, R.B.D. (1980). Effects of light and leaching on germination of saffron thistle Carthamus lanatus L. Australian Journal of Plant Physiology 7,587-94.
Acknowledgments:
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