|
Ragwort seed has often been reported to have a very low fertility or germination rates in the order of 1% to 3%.
In the wild, ragwort in fact has two germination requirements. When these requirements are met, ragwort has been shown to commonly have fertility levels of 60% to 80% (Germination trials - Ragwort-UK Ltd - 2001,2003).
Those germination requirement are:-
- The seed must be washed to remove inhibitor chemicals. The amount of washing can be achieved during a week of steady rainfall. The washing does not have to happen all in one episode, it can be achieved over several separate, small showers.
- The seed, having been washed, must receive sunlight through its seedcase in order to stimulate germination.
Where ragwort seed has been washed but is blocked from light by plant cover or a thin layer of soil, the seeds do not germinate, however, they are able to remain viable for several years. If they are subsequently exposed to sunlight, they will rapidly germinate.
This gives rise to the observation that dense vegetation cover holds back ragwort germination much better than bare ground or sparse vegetation. It is a fact that strong grass cover will dramatically suppress ragwort germination. However, it is a fallacy to believe that strong grass cover can prevent ragwort germination. There are many agents at work in strong grassland - in particular ants and earthworms - which regularly bring large amounts of soil up to the light. When soil seed levels start to escalate as they are at the moment, then many seeds reach the sunlight and consequently germinate.
For proof of this, look no further than our roadside verges, these are generally places of high fertility and dense vegetation requiring control by mowing several times a year to keep the plant growth in check. Yet despite the density of grass coverage, ragwort has colonised significant percentages of this undisturbed land.
Ragwort is invasive, highly fertile, and capable of invading virtually all undisturbed land when the soil seed density reaches high enough levels. As ragwort plants produce typically ca 150,000 seeds per plant and that seed is long lived, it is not long before land reaches the seed densities necessary to trigger germination with the consequence that ragwort has extended its range still further.
|
