Thistles
General description and types
Thistles are both biennial and perennial weeds of which there are 14 different species in the UK alone however three types are usually observed on poorly maintained sports fields:
🌿Creeping Thistle (perennial) the most common, has spiny leaves often covered with white hairs sprouting from spineless stems producing lilac flowers although these will not normally be observed in managed turf.
🌿Dwarf Thistle (perennial) by comparison has a redish purple flower but the main point of difference is that it is almost stemless mainly displaying a rosette of spiny leaves.
🌿Spear Thistles (biennial) create large, short stalked rosettes of dull, hairy long spined leaves that are the most unpleasant if handled, they typically wont flower on maintained areas as the flowers appear when the weed becomes taller.
✅In what conditions do they thrive?
Creeping Thistle is happy in most soil types but does best in newly sown areas and can be observed in new pitch projects before a regular mowing regime is established. Dwarf Thistle favours mainly chalky alkaline soils whilst Spear Thistle does well in most soil types but is most often observed where soils has been disturbed through cultivation.
⚽ What are the effects on turf?
Creeping Thistle is usually the most problematic as it can spread both through seed and creeping underground roots meaning formation of the seed head is not necessary for spread unlike the other thistles mentioned. If left untreated the population can spread by 6-12 metres per year. Thistle seed can remain viable in the soil for many years with Creeping Thistle up to 20 years in undisturbed soil. Given the size of this weed it can quickly smother and kill surrounding grass.
Management
Cultural
🌿Thistles as a rule don’t tolerate regular mowing so this should usually be adequate to control them.
🌿As with many weeds they are encouraged by poorly maintained worn turf where areas of bare ground exist. A good maintenance regime is the first line of defence.
🌿Small populations of thistles can be removed by hand but take care as the spined leaves are sharp.
Chemical
🧪Spot treatment can be effective if there is a limited population.
🧪Where populations are more widespread thistles will be controlled through application of broad-spectrum selective herbicide when growing. (Do not apply under drought conditions, application will not be effective and may damage the grass sward).
🧪One application is normally sufficient.
🧪 Selective herbicides should only ever be applied by a fully qualified professional with the appropriate equipment and paperwork.
🧪Always try and minimise use of chemicals wear possible. Seek guidance from BASIS certificated advisors and use contractors abiding by The Amenity Standard scheme.