Establishing Yellow Rattle, Rhinanthus minor

Spring is well underway, the grass is growing and the Yellow Rattle Rhinanthus minor is germinating in the hay meadows. It is also germinating in profusion in many of the areas that we mulched with grass and hay from Cae Mari Jones last summer and autumn.

Yellow Rattle (Rhinanthus minor) seedlings germinating in hay mulch

Yellow Rattle (Rhinanthus minor) seedlings germinating in hay mulch

There has been a lot of interest in the role Yellow Rattle can play in the establishment and maintenance of wildflower meadows. It is semi-parasitic on grass, reducing it’s vigour and allowing the establishment of a wider range of flora in the meadow.

We have found mulch a very successful method for establishing Yellow Rattle in new areas, all be it unintentionally!

We aim to cut the majority of Cae Mari Jones (with a scythe) every year, starting in early July after the flowers have set seed. This management is necessary for the benefit of the wildflowers, but provides much more grass then we need to make into hay for our livestock and spring hay mulching needs. The excess grass is wilted for a day or two, then used very productively as a mulch, often on areas of perennial edibles (more information on how we use various mulches to follow).

Yellow Rattle (Rhinanthus minor) in one of the Trust's hay fields

Yellow Rattle (Rhinanthus minor) in one of the Trust’s hay fields

The mulch is, of course, full of seed from the meadow. Yellow Rattle establishes best from fresh seed and needs a very short sward or even clear ground in Spring to germinate in.

The mulch comes complete with fresh seed and creates the open conditions that the rattle needs. Seedlings in the centre of the bed seldom thrive but those on the edge, that are able to parasitise the grass on the bordering path/track grow away strongly if allowed. The Yellow Rattle can then seed and spread into the adjacent grassland, providing it is managed in such a way as to encourage it.

It is important to note that Yellow Rattle seed needs exposure to the cold temperatures of winter whilst in the moist soil to break dormency and germinate. We do not find yellow rattle germinating in beds mulched with hay in the spring, only in those where mulch has been in place since the previous summer or from hay mulch in the autumn.

We haven’t tried to use this method to establish Yellow Rattle in grassland where it is absent – we have plenty of it! If you have grass in which you would like to establish Yellow Rattle I can imagine the following method working.

  • Cut the grass short in July (as if it had been cut for hay).
  • Place patches of fresh grass cut from a meadow containing Yellow Rattle amongst the grass, thick enough that they will suppress the grass and provide a bare spot for the rattle to establish in (we mulch our bed with up to 2ft of hay, although this may be more then necessary for rattle establishment).
  • Manage the grassland to encourage the rattle (cut/graze the grass short in the Autumn such that it is short going into the Winter. Leave it to grow long in the spring then cut short in July after the rattle has seeded. Whenever the grass is cut the arisings should be removed, either as hay or otherwise.)
  • Of course, you would need to find a farm that has rattle in it’s hay fields to source grass from. Certainly in our area of Wales there are more such fields about then you might expect. Let us know if you have a go – I would be interested to hear if it works!

    Rattle Seed Heads. The sound of the seeds rattling in the seed cases may give the plant it's name.

    Rattle Seed Heads. The sound of the seeds rattling in the seed cases may give the plant it’s name.

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