Friday, 21 August 2009

Yellow Peril

Common Ragwort is a biennial plant of grassland. Basal leaves only develop the year it germinates, with flowering in the second year (after which it dies). It establishes where the ground is disturbed. It is considered poisonous to livestock, but grazing animals avoid eating it unless it is accidentally harvested with hay (then they cannot see it).

There have been many debates about how to manage ragwort. If pulled when in flower some roots are often left in the ground. This turns it into a perennial (meaning it will re-grow next year). Studies on ragwort indicate that to reduce the quantity of ragwort in pasture, the following approaches are recommended:
  1. Remove or reduce the source of any disturbance to the grassland (e.g. rabbits, overgrazing, harrowing) - if the ground is not disturbed, then the plant cannot spread by seed into new areas.
  2. Allow existing plants to flower, after which (being biennial) they will die.
This is the advice I have given this summer to the Trustees, who need to consider how to address the infestation of pastures at Freeman's Marsh by ragwort.

It may also be possible to use herbicide sprays to kill individual plants in spring, when the basal rosettes are visible, but if there is a heavy infestation this is not advised. Spraying will also open up bare ground - where seedlings will be able to germinate.

The advice I have given is based on scientific studies of the plant carried out by Professor Mick Crawley at Imperial College.

In a hay meadow, it is vital to pull the ragwort before the hay is cut. However, a well managed hay meadow will contain little ragwort. Pastures are more prone to ragwort infestation if they are grazed by too many animals or grazed when the ground is wet, which creates areas of bare ground. Rabbits can also cause considerable pasture damage - ragwort is often abundant on railway banks around rabbit warrens.

More information on ragwort is available online here and here.

Wednesday, 29 July 2009

Cows on Freeman's Marsh

Grazing is vital to maintain the wild flora of Freeman's Marsh. Without grazing, the marsh would be dominated by coarse grasses, rushes and, eventually, trees! It is really difficult getting the balance of grazing right. This year the Trustees have put out fewer cattle on the marsh but it is possible that with the rainy weather the most special part of the site could be undergrazed.

Water crowfoot on the River Dun

What a brilliant display of water crowfoot on the River Dun this year! Despite ongoing problems with pollution originating from the leaky and murky K&A Canal. Photo taken May 2009.
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