Saffron Thistle Carthamus lanatus
Origin: Europe, W Asia, N Africa
Distribution in Canberra Region: Small infestations are widespread in most parts of CNP: major infestations in some larger grassland areas especially where sheep grazed in the past, e.g. Coolamon Ridge, Mt Painter, Mt Ainslie/Majura (dominant species in areas 30x30 m in parts of these areas). Can grow in poor soils and rocky terrain.
The pattern of infestation in a reserve may vary considerably from year to year depending on weather conditions and on what control methods were applied the previous season.
CUPP areas less affected. Farmlands heavily or lightly infested � related to livestock.
Dispersal: Mostly local, by seeds which fall from seedheads or are windblown over short distances, or carried downhill on slopes by rain; or carried by livestock/kangaroos.
General description and biology
Saffron thistles are annual, erect, up to 1 m high; stalk to 2-3 cm thick but usually < 1 cm, much branched at the ends.
Pale green narrow triangular stem-clasping leaves with no stalk, ending in a spike.
Most of the plant covered with minute hairs.
Flowers bright yellow, on ends of stalk or branches.
Saffrons grow rapidly from rosettes in spring, flowering about December to February.
A second crop commonly occurs later, March-May.
They are prolific seed-bearers and strong competitors, capable of supplanting everything else.
Seeds can remain dormant in the soil and germinate up to 10 years later.
Infestation is less abundant where there is adequate grass cover.
Control methods
a. Manual methods
Can be pulled out by hand; or cut off with secateurs (small or large) or brushcutter.
Unlike other common thistles, they usually grow again when cut, if cut before flowering.
For heavily infested and larger areas a brushcutter with nylon blades is recommended;
but large secateurs/loppers for stems >1 cm thick.
Slashing should be done when the yellow flower has formed but not yet produced seed.
Slashing before flowering or once the flower has wilted and is beginning to set seed is hardly useful � although it may throw seed to the ground that will germinate at the wrong time or be destroyed by insects, birds etc.
Slashing should thus be optimally done by January and becomes progressively less effective as the season advances.
Persistent slashing over a period of years can eradicate saffrons, but crucially: be timely.
The rosettes can be quite easily dug out or cut off just below ground level with a mattock or mini-pick; less easily, with loppers.
Getting saffron thistles at the rosette stage (especially in spring) is ultimately the best strategy, together with collecting dried-up seedheads.
If plants have gone to seed, picking off the seedheads and bagging/composting them is effective but labour-intensive!
b. Chemical methods
Sprays are effective if applied early (spring), before the plants produce flowers; essentially, to rosettes.
For relatively small areas spot-spraying can be done by knapsack spray.
For large areas a motorized pump with long hose is appropriate.
For the spray to be effective the rosettes must not be covered by grasses. So it is usually necessary to mow the grass first (if the terrain is not too stony or steep) or to introduce livestock to graze it.
The spray to be used is a specific herbicide.
Contact CNP/CUPP for advice � since spraying is only done by the Parks and Conservation service, or by a technically qualified contractor; not by volunteers.
The above information is provided only to enable park-care groups to make appropriate plans and suggestions to CNP/CUPP. See also important paragraph on Limitations, #4.