ARC's Gems in the Dune Project Manager, Fiona Sunners explains why this rare and tiny "lettice of the coast" has disappeared from sand dunes and what can be done to help.

It’s winter – where better to be than crawling on your hands and knees in the sand dunes! And what are we looking for I hear you ask? Yet another of the small specialties of the Sefton coast – tiny (3-10mm diameter), vivid green rosettes – petalwort, the miniature lettuce of the coast, hidden on well-worn or grazed pathways and at the edges of dune slacks in the sand dunes.

Little Gem lettuce Petalwort

Our target at the start of the Gems in the Dunes project was to see if this tiny plant existed in more than four locations on the Sefton coast!

Back in 1997 there were just under 8000 plants, across seven locations, mainly just to the north of Sands Lake in Ainsdale. However, since then, the landscape has changed, the amount of rabbit grazing has fallen and footfall along key areas has reduced. Pathways, where petalwort once thrived have changed in appearance from that similar to a bowling green (short well cropped turf), to rough grassland with no signs of sand movement – not great for many species in a sand dune system. By 2013 petalwort was known at only four locations and only 100 individuals had been counted. Why had it disappeared so quickly – let me tell you.

Petalwort is one of many plants that thrive in dunes which are in a fairly early development stage – although too early and it is too sandy for them. It prefers slacks that are typically well grazed, with damp calcareous sand that floods occasionally, although continued flooding is not ideal. It also likes small amounts of freshly blown sand – so not picky at all! On top of this It is not a very mobile plant, with spores requiring water to disperse, so often they are only transported a few metres from parent plants.

In the past, this type of habitat developed a lot more often and succession happened at a much slower pace. Today, fewer grazing rabbits, fewer visitors, changes in the climate as well as increased levels of nitrogen are speeding up the process of coastal change, meaning the small amount of suitable habitat we have, is disappearing very quickly. This is a problem for many dune specialties, not just petalwort.

So, how have we got on? We firstly started with some training for coastal staff and volunteers to discover the ‘what, where’s and how’s’ of petalwort. Basically, it is small (3-10mm typical diameter) and green, with two flat leaf-like structures on either side of a midrib and near parallel ridges known a lamellae radiating from the midrib. An underground rhizome anchors it in place and provides a nutrient resource. It likes areas with short incomplete vegetation cover. There are male plants, which develop antheridia (small green/yellow balls) and females that have frilly bracts (leafy bits) at the centre of the lamellae. Males and females need to be within centimetres of each other for sexual reproduction to take place. Oh and is most visible from October to early spring.

Male petalwort Female petalwort

Once we knew what we were looking for we started to survey, starting out by crawling round at the last four locations recorded in 2013, followed by the locations from the 1990s reports. As well as similar looking habitat nearby. We had some good days and some even better days! Some of our eagle-eyed volunteers could almost spot it from a mile off, whilst others had a look, lost patience and turned their attention to other tasks! At many of the 1990s locations either grasses or creeping willow had become the dominant force, so no more petalwort. However, there are numerous well-worn pathways running through the dunes, and on some of these, we did strike lucky! Volunteers helped us to find it at a dozen new locations and counted over 2500 individuals – well done volunteers.

The speed of change on the coast is incredible, and even during the project we have seen the amount of vegetation increase dramatically and in some places where we found plants at the start of the project (2017/18), we have not been able to find plants this winter (3yrs on)! We know that it reproduces by spores and that spores from many species can often remain in the ground waiting for favourable conditions before they germinate. So last winter (2019/20) we went out with one of the volunteers and scraped the turf away from three small areas where there were records in the 1990s. This winter (2020/21), at two of the three patches we counted small numbers of petalwort, however even these small patches are starting to vegetate up once again. Future creation and maintenance of more of these patches, at suitable locations could see numbers increase once again!

If you would like to find out more about this picky little plant, take a look at our Petalwort Species Information Guide.