RAGWORT  (senecio jacobaea)

This striking plant was once a considerable rarity.  When farmers depended heavily on forage production and had large numbers of farm staff, any Ragwort plant was meticulously rooted out and destroyed. However, for the past 12 years Ragwort has staged a seemingly unstoppable comeback, and is now a commonplace kerbside flower.

Plants range in stature from as little as 20 cm to a majestic 2 metre depending on the fertility of the soil they invade. Ragwort is famous for its ‘GROW ANYWHERE - SEED EVERYWHERE’  capabilities and apart from human intervention, the plant  only has the larvae of the Cinnabar moth as an effective predator.  Its acrid smell, bitter taste and natural toxicity give it a virtually unchecked opportunity to multiply.

Designated a ‘Harmful Weed’ under the 1959 Weed Act, Ragwort is normally biennial. It germinates in bare patches of ground and spends the first year as a small rosette close to the ground developing a substantial root system and a bulbous storage rhizome in preparation for rapid growth and colonisation the second year. The flat nature of the rosettes, mean that they are missed by mowing and by ‘Strip and Burn’ teams.

Ragwort is highly invasive and will rapidly degrade and take over grazing land.  Because of its smell and taste, stock leave the Ragwort alone allowing it to reproduce and colonise rapidly.

This square metre of rough pasture hosted over 140 plants - that’s nearly 1.5 million plants to the hectare - and there are many thousands of hectares degraded to this level and worse.

The plant can withstand severe frost (-7^oC for over 3 days), immersion flooding for several weeks, and because of its large root system, can survive extreme drought.

In it’s second year, as soon as the temperature rises, rosettes extend to start the formation of flowering spikes. In urban environments, where temperatures may be several degrees warmer than the countryside, Ragwort has reached flowering and seeding by mid May.  However, on kerbsides, waste land and grazing meadows growth is slower, such that it is not until June that plants have formed multiple woody stems. Each stem is multi branched, and each branch carries many flower heads. Plants typically achieve 2 ft to 5 ft, and have been recorded achieving over 7 ft in height in rich soils.

At the moment, small numbers of Cinnabar cling to the edge of survival, and due to the ravages of intense predation, they achieve little more than superficial damage to the large stocks of Ragwort. In order to effect significant change in the survival rate of Ragwort, the moth and caterpillar must outnumber predators by a significant proportion.  When this occurs, moth numbers will increase rapidly until they become commonplace. Only then will the caterpillar levels be adequate to bring the plague of Ragwort under control.