Yellow rattle

[Claire]

I started to cast yellow rattle into my meadow 5 years ago. It had become very grass heavy. It’s been grazed each winter for a very short period- a few weeks.
The rattle took really well and last year there was so much we decided this year we would harvest some seed. However this year I have had to search for the rattle there is so little !
Last winter was the first year we neither grazed or cut the meadow but I find it hard to believe that has caused this.
Has anyone had a similar experience ?
We are at Moreleigh. Thank you.

[Steve Pollard]

Claire, if you had an abundance of rattle last year, there are really only two reasons why you wouldn't have it this year. 1. the rattle was grazed after germinating in mid-spring this year. 2. the sward was not open enough for the rattle to successfully germinate into this spring. From what you say, I'm sure it was the latter. Yellow rattle is an annual plant common in haymeadows, and as such, unlike almost all other meadow plants, it has to grow anew year. It is common in haymeadows because the sward is cut short at least once a year, so that when the seeds germinate in spring they have light and space to grow into before establishing their parasitisation of nearby plants. As your meadow was uncut, the seedlings were out-competed in the closed sward. Generally, the optimal management for yellow rattle is a late-summer cut, followed by sufficient aftermath grazing to ensure that the sward is as short as possible for germination in early-spring. I'm sorry!

[Robin]

I wonder if the mild winter was a contributory factor. Yellow rattle needs frost to germinate and there weren't many nights that cold.

[Claire]

Thank you Robin and Steve for your answers.
The lack of cold temps during the winter must have played its part.
Yes the second point about the yellow rattle being crowded out by grasses as we didn’t cut or graze makes complete sense.
Grazing has now become difficult so we will make sure the meadow gets a really good cut this year. It will be interesting to see what happens next Spring. Thanks again.

[Robin]

If you had very little in flower this year, you may not see much next Spring, as Yellow Rattle is an annual. It might be wise to sow some more seed this autumn.

[Steve Pollard]

Claire, it's a very common misconception that the seeds need frost in order to germinate - if that were the case, rattle would also have vanished from other nearby meadows, when actually it did not. According to the definitive work on the species by Duncan Westbury (attached), about 3 months at temperatures between 2 °C and 6 °C are required to break seed dormancy. I think the misconception stems from the fact that the seeds are sometimes put in freezers to artificially simulate winter stratification. To add an anecdote to the cause being due to not mowing - in my haymeadows, which already have little grass in them, I sometimes leave an uncut strip in the middle of the field as invertebrate habitat, these strips are then aftermath grazed, so that by the end of winter, they aren't actually readily distinguishable from the rest of the field. However, in the following summer rattle plants are far less abundant in the uncut strips, despite the climate and other factors being the same. Given you do have some rattle plants this year, if managed correctly, it will bounce back within a couple of years. Good luck.