Hybrid Woundwort

Its that time of year when I need to delve back into the archives to keep the blog ticking over. Here is a nice find from back in July at Clumpcliffe (VC63). If only all hybrids were so satisfyingly intermediate.

Hybrid Woundwort (Stachys x ambigua) is the cross between Hedge Woundwort (Stachys sylvatica) and Marsh Woundwort (Stachys palustris) and can maintain itself through vegetative spread. This clone has the flowers of the former, and the foliage of the latter BUT with petioles of intermediate length. The foliage has some of the pungency of Hedge Woundwort, but this trait is much reduced,

It is a widespread hybrid (see BSBI Distribution Database) so is worth keeping an eye out for in damp places.

A Magnificence of Mulleins (VC31)

Sarah Lambert has recently provided an exciting list of plants found on the old Conington dump (no public access), which she has been studying for a number of years. This really is a botanical hotspot and supports a variety of species more typical of the chalk, no doubt arriving with imported substrate. This includes Wild Candytuft (Iberis amara), Wall Bedstraw (Galium parisiense) and an exciting number of Mulleins (Verbascum species). Many of the latter are known no where else in the county.

See Sarah's blog for an account in her own words and from which I have borrowed a photo (below) of Hoary Mullein (Verbascum pulverulentum).

Invasion of the False Natives

Lookalikes (species similar to and planted in mistake for native species) and false natives (infraspecific taxa of foreign origin) have slowly been growing in profile over recent years following Peter Sell bringing these to a wider audience, and then the inclusion of a number of such plants in Edition 3 of Clive Stace's New Flora of the British Isles. But there is still some way to go in understanding the true distribution of these taxa, and the long term implications of 30 years zealous tree and shrub planting as quick fix habitat mitigation and creation.

Southern Dogwood (Cornus australis or Cornus sanguinea subsp. australis) is one good case in point, with the following map showing a rash of dots across central England. This species is almost ubiquitous in recent plantings in VC31, and is increasingly being found bird sown. A similar picture is building in VC64. My personal view is that this isn't a trivial matter. Southern Dogwood seems to grow more vigorously and forms a much denser bush, so I can see it being a problem for habitat managers in the future. It is obvious why horticulturists have favoured it as it has larger flowers and leaves than the native plant, produces a neater denser bush and has brilliant autumn colour.



The characters used in keys to distinguish it from Dogwood (Cornus sanguinea) are subtle and based on the number of leaf veins and the morphology of leaf hairs, but this belies the genuine differences between the two species. The leaf hair differences, visible with a hand lens, are well illustrated on the Manual of the Alien Plants of Belgium website. Once known the two species can usually be told at a glance with very high accuracy, but it always advisable to check the hairs. More recorders need to be looking for and distinguishing the two species if we are to have a representative picture of their true range in time for the next Atlas.

The typical large and rounded foliage of Southern Dogwood

The hybrid hawthorn Crataegus x subsphaerica is the subject of a separate post which can be found here. But I just wanted to show the current map of is distribution in VC63 and 64 following targeted searches this autumn. Note the two new locations well to the north of the Leeds cluster. It will be interesting to see how many new dots are added in 2017, I suspect it is going to prove very widespread and abundant.

What is interesting about my find at Moor Monkton (VC64) is that the original planted trees appear to have produced new trees much closer to Hawthorn (Crataegus monogyna) than the original stock. This suggests backcrossing, and this will add to identification difficulties in the future. Similar backcrossed bushes were found bird sown at Knostrop where there is a hedgerow dominated by the hybrid and estimated to be 30 years old. Clearly the hybrid has been with us for a while and has had plenty of time for birds to spread it around, so hybrids could potentially turn up anywhere.

Where There's Muck - Part II

So the visits to sewage works have continued and, despite the lateness of the season, so have the nice finds. They really are fascinating sites and a lesson in the resilience of seeds. At one site there was a veritable fruit salad with the mandatory Fig (Ficus carica) and Tomato (Solanum lycopersicum) being joined by Cape Gooseberry (Physalis peruviana), Strawberry (Fragaria ananassa) and even a well established Grape Vine (Vitis vinifera).

Life behind bars! - Fig tree making its way into the light(?) of autumnal Dewsbury (VC63)

This one has really got its roots down, that's one happy Fig - Knostrop (VC64)

Cape Gooseberry at Harrogate (VC64) - where else, Tomatos are so last year

Or how about this as an oddity, no idea what this says about the diet of people in Dewsbury!

Orange Bladder-senna (Colutea x media) - Dewsbury (VC63)

However, the best find for me of the last few weeks had to be the huge population (1000's) of Musk Stork's-bill (Erodium moschatum) at Knostrop (VC64). Nothing to do with the sewage treatment process, but it obviously liked the management regime at the site.

Photo by Dick Culbert from Wikimedia Commons

A Headache of Hawthorns

The 3rd Edition of Stace back in 2010 introduced Large-sepalled Hawthorn (Crataegus rhipidophylla) to British botanists, and encouraged me to start looking at hawthorns more closely. Away from ancient woodlands it was perhaps too easy to get blasé and expect Hawthorn (Crataegus monogyna) or its hybrid Crataegus x media. Sure enough, I first met with this species in Lincolnshire and I have found it in scattered locations thereafter. It is not common and, currently at least, is primarily of planted origin. However, it is undoubtedly under-recorded and other botanists should be looking more critically.

Large-sepalled Hawthorn stands out in the spring with its early and large flowers. The leaves are distinctive being redolent of Wild Service-tree (Sorbus torminalis) in outline with a saw-edged base to the leaf. In the autumn the large and typically barrel-shaped fruit appear and typically have erect sepals (depending on variety) that are longer than wide. What is also distinctive in the autumn is the early colour change and leaf drop, which starts in October well before Hawthorn and its kin.

Much more common than Large-sepalled Hawthorn is its offspring with Hawthorn i.e. Crataegus x subsphaerica. Indeed, having targeted this species this October I can say it is very common, undoubtedly overlooked and likely to be a real headache for botanists in the future. What has become most apparent to me over the last few weeks is just how variable this species is. In some guises it can easily be overlooked as Hawthorn or Crataegus x media when not in fruit. By the time the BSBI starts to think about the next Atlas (after the current 2020 project) it will likely be so ingrained in our countryside that we will become dependent on examination of fruit for definitive identifications.

When I first found C. x subsphaerica it was as the optimal form for ID i.e. hybrid vigour, leaves with the outline and toothing of Large-sepalled Hawthorn but the dissection of Hawthorn (forms with the influence of the heavily dissected monogyna f. schizophylla are particularly distinctive), and large fruit with erect sepals. However, all intermediates occur and now is a good time to look while leaves and fruits are still present. The leaves on different bushes can show every range of variation between the two parents. Leaves may have the saw-edge of Large-sepalled, or this can be reduced or vary from leaf to leaf, or can be absent entirely. The fruit size can vary from small to large. However, if there are erect sepals on the fruit (nothovar. domicensis) you can be confident of the ID. Note this character develops as the fruit mature, so don't make assumptions based on immature fruit.

This is the current distribution of the hybrid based on data in the BSBI database, and reflects where people are looking rather than the true distribution. It will only be the tip of the iceberg. My experiences around my local patch will undoubtedly be replicated across much of England and Wales, if not the UK as a whole.

Finally, to round off the hawthorns, a return visit to the fabulous large fruited (>1cm) form of Hawthorn (var. splendens). It is a stunning sight when you meet a bush of this in full fruit, dripping like jewels in a particularly vibrant shade of red. Despite the fact that this variety only occurs at very low density, i.e. one or two bushes here or there, it does seem more than a chance mutation. While the fruits of var. monogyna (and subsp. nordica if you follow Sell & Murrell, but the distinction betwen subspecies monogyna and nordica does not seem worth maintaining) and var. splendens do seem to vary in size on a single bush there does seem to be a well marked cut off in the size ranges between the two varieties. In other words, the fruit vary in size around their respective means, but do not grade into each other. A reasonable working hypothesis to explain this might be that the latter has a higher ploidy level.

Where There's Muck ...

Sewage Works are not the most glamorous of locations but they are always interesting places to visit (with work I should add - not my normal idea of a good day out!). This time of year is particularly good when all sorts of rarities pop up in composting and other marginal areas.

Yesterday rewarded me and my colleague Hannah with several plants of the stunning Apple-of-Peru (Nicandra physalodes var. violacea) at Esholt (VC64). The colour and size of the flowers never fail to impress and seem out of place on a grey autumn day.

We were also rewarded with a single plant of Cape-gooseberry (Physalis peruviana), unfortunately not in flower. Here are a couple of photos taken at Knostrop, Leeds (VC64) a couple of years back. It has also been seen recently elsewhere in the VC near Spofforth.

And to round off an interesting trip we found one plant of the hybrid between Oxford Ragwort and Sticky Groundsel (Senecio x subnebrodensis) growing with both parents. I was too excited to take a photo, but there is a reliable image here. This find nicely updates an old record for this area by Jesse Tregale.

Unwelcome Invader at Hemingford Grey (VC31)

Lynne Farrell found Floating Pennywort in the River Great Ouse at Hemingford today. This is a very invasive non-native species that will hopefully be eradicated before it has chance to establish. It would be very unfortunate if it got a foothold and then moved onto colonise the important gravel pit complexes along the river.

Floating Pennywort is a native of North America, but was introduced to Britain by the horticultural trade as an aquatic ornamental. As is too often the case with aquatics, it is a bit of a thug and once it starts to take over its not long before someone thinks it a good idea to turf it out into the nearest watercourse. Spread is somewhat inevitable after that, with this species capable of growing 20cm per day.

This species is well established at Bedford (VC30), so there is a high chance of it being washed downstream into Huntingdonshire. Please keep your eyes peeled, and if you see it report it via the Plant Tracker website or phone app, or by email to alert_nonnative@ceh.ac.uk.

For readers from Yorkshire, it is also depressingly frequent in the Rivers Don, Aire and Calder.