There are several varieties of common thistles which are quite easy to control while Artichoke Thistle is more difficult.
Artichoke Thistle
Scotch Thistle
COMMON THISTLES
Common thistles may be removed by hand if their numbers are small, though the risk of regrowth from the roots is high. (If you are cutting them with a hoe, many will regrow unless you get right down into the root system)
Larger infestations of common thistles may be successfully sprayed. The best time to do this is while they are small, usually when all the pasture has germinated in the autumn. Because of the seed bank in the soil some thistles are very difficult to eradicate. Others are quick to return if there is weak or no pasture present, however autumn broad leaf spraying and strong pastures will largely control scotch, spear, slender and shore thistles. Golden and variegated thistles will be significantly reduced.
Late autumn to early winter is the best time to use a broad leaf spray, no only to remove thistles from your pastures, but also to control a wide range of other broad leaf weeds which reduce their vigour. If you miss this time period then it is still possible for us to spray right through until late spring, however weed control will be less assured.
RED-LEGGED EARTH MITES
If the pasture we are spraying for broad leaf weeds and thistles has a lot of clover in it, we may suggest using an insecticide to control red legged earth mites. If they are a significant problem, there is a specific control program which RVFS can implement for you.
ARTICHOKE THISTLE
This thistle is more difficult to remove from pasture by boom spraying. It requires more expensive chemicals and can take many years to gain control.
If possible remove by hand or by spot spraying.
Recommended time of treatment is late winter.