Winter Flowering

New Year Plant Hunt 2018

Grantham Ecology2 Comments

BSBI‘s annual New Year Plant Hunt is a great way to experience this, as well as contribute your data to a national recording scheme. Everybody is welcome to get involved – even if this is just spotting a daisy on the lawn or gorse flowering by the roadside on your way to work!

I’ve walked the same New Year Plant Hunt route at the beginning of each month since January 2017 and thought it would be interesting to view the results of the January 2018 hunt in the context of the year passed.

I would caveat this by saying it is very sketchy data to base any assumptions on so this should be considered ‘observations and possible trends’ rather than anything more robust. It is a single transect, over a single year in a single geographic location. It is  also along a route which is incidentally prone to the machinations of land owners and council contractors being focused on streets, parks and carparks. This means that species which I know to have been in flower can disappear from the record because somebody has tidied up the only place in my transect where they grow. This could account for gaps in particular species which does not actually have any reflection on their ecology! Furthermore, these records may relate to a single individual with a single flower being found on the transect – it has nothing to do with abundance or dominance. I found one tatty cow parsley in flower in January 2018 but there were swathes of them flowering in  April 2017 – presence may relate to exceptions and outliers rather than reflecting standard flowering ecology.

The Constants

There are a number of species I picked up on the 2018 New Year Plant Hunt which I had found in flower every month of previous year along the same transect route. In all, 50% of the flowers I found in January 2018 had been recorded flowering along the transect in 9 or more months during the previous year.

The species recorded in every single month were daisy, ivy-leaved toadflax, white deadnettle and shepherd’s purse. Alongside these were a number of species where I had only missed them in either one or two months in the previous year – these included annual meadowgrass, sun spurge, oxford ragwort, common chickweed, snapdragon (naturalised), yarrow, Guernsey fleabane and petty spurge.

constants
The ‘Constants’ – these were from photographs taken throughout the year and not taken on the day – the dark start and lunchtime rain made photography difficult!

Interestingly, the missing months when I hadn’t found these individual species in flower were clustered around March/April time but in all cases, they had been consistently in flower since September. This could indicate a flowering season which is all year round, or could represent a long flowering season which begins in the late spring and continues to early spring depending on the winter weather for duration. It could also represent an anthropogenic phenomena I noticed which was that winter ‘weeds’ were often ignored in January to March but a colony was often wiped out when the weather warmed up and people turned their attention to de-greening the edges of pavements!

Long-season species

Those species found flowering in only nine months in 2017 continue the distribution trend noticed in the near-constants – feverfew and hedge mustard were found in January 2017 and 2018 but disappeared between February and April 2017 to then reappear and remain for the rest of the year. Hedgerow cranesbill and wall barley similarly disappeared between February and May and have been constant since.

Species with a lower number of records, perhaps considered more late-season than long-season, appeared in later-summer/autumn 2017 and persisted through the winter to January including bramble, blue fleabane and Canadian fleabane.

long season.jpg
The long- or late-season specialists – these were from photographs taken throughout the year and not taken on the day – the dark start and lunchtime rain made photography difficult!

These would accord with previous interpretations by BSBI scientists who concluded that most of the New Year Plant Hunt finds in 2017 were hangers-on from the last season rather than early arrivals from the new season. Late flowering and long flowering species might be expected to be particularly prone to this.

Winter/Spring Specialists

Several species recorded showed a markedly winter flowering period – winter heliotrope being the key example but alder and oragan grape also according with this pattern. Naturalised wood spurge and greater periwinkle also fit into this category, though their season seemed longer.

Cow parsley and  bittercress both showed a predominantly spring flowering pattern, but with sporadic flowering during the winter months as well.

Red dead nettle showed an interesting distribution – it went missing in the middle of the year between June and September but remained fairly constant otherwise. This almost indicates a winter-flowering strategy but with a much longer timeframe than things like alder which appear in flower only for a month or two. It could however be due to management removing the regular plants on my transect, resulting in an apparent gap in what is actually a constant species. Repeating the transects in 2018 would help clarify this!

spring1.jpg
The winter or spring flowering specialists – these were from photographs taken throughout the year and not taken on the day – the dark start and lunchtime rain made photography difficult!

 

Conclusion

Accounting for the various caveats in the data, there do appear to be three key categories to which the species flowering on my 2018 New Year Plant Hunt accord. Those which flower almost year-round; those which have a late flowering distribution which hangs on into winter; and those which are winter or early-spring flowering specialists.

I totted up 31 species on the regular transect of the New Year Plant Hunt, which is just under 20% of the total number of species I recorded across the year. What is missing from the transect in January is a host of spring flowers which will not appear for another month or two (such as violets, naturalised spring bulbs and woodland species such as ramsons); the vast majority of the trees and grasses; and the dominant summer species which flowered between May and July (such as hedge parsley, meadowsweet and black knapweed). Also missing are some of the autumn specialists with shorter flowering seasons (including ivy, Russian vine and Michaelmas daisy).

I do however hope to continue the transects through 2018 and build a more robust dataset over time as I think the context it adds to the new year plant hunt is quite an interesting one!

Find out more about the BSBI’s 2018 New Year Plant Hunt results on their website here!

Why does gorse flower in the winter?

Grantham Ecology4 Comments

At this time of year, the world in general (and Grantham in particular) can seem a rather bleak place. Trees are nothing but bare boughs, the grass is wet and sodden underfoot and the only flowers to be seen are those in the supermarket containers or the florists’ window. But there is a notable exception to this general rule.

On the south-eastern edge of the town, the fields rise up above the estates at the end of Gorse Road. This area is described as ‘Gorse Lawn’ on the OS map and rises up Hall Hill, on the edge of the Hills and Hollows. Walking over a small stile and scattering rabbits which are nibbling the tips off grass poking above the frost, you are soon surrounded by gorse – latin name Ulex europaeus. Even now, in the middle of January when the bulbs are only beginning to push up through the earth, the gorse growing on this hillside present yellow flowers in abundance.

You will almost certainly know gorse, if not by name then by sight. It is one of our prickliest shrubs and grows not only on heaths, where it compliments the purple heather beautifully, but on all kinds of waste ground, flourishing where the soil is shallow and nutrients are scarce. It loves sunny spots and often grows on sandy soils. It is a member of the pea family along with garden peas and beans, garden flowers such as lupins and even trees such as laburnum. The clue is in the lipped, irregular flowers.

Perhaps the most interesting question is quite why the gorse is flowering so profusely in the dead of winter. Flowers are clearly designed for greater things than simply decorating our houses, and butterflies and bees aren’t just taking a rest when the alight. The flowers attract insects through the offer of nectar and use the insects to pass the pollen, from one plant to the next and, so, fertilise them. The flowering season then is designed to coincide with the warmer weather, when most of the insects take to the air. Some plants flower early, some late, some in the middle, but almost none choose to bloom at the one time when insects are in such short supply as mid-winter. So why is the gorse such an exception?

Gorse flowers

A wonderful paper from the Linnean Society journal in November 1869 looked at a number of species which flowered at this most unusual time and concluded that the flowers are all arranged so that they can fertilise themselves without even opening the flowers, thereby ensuring that fertile seeds can be made even if the snow arrives and remains, and if no insects come to call. This ability of gorse to produce lots of clones of itself is part of the reason why it is such an invasive species in countries such as the United States.

This ability to reproduce without insects allows the winter flowering strategy without risk of a barren year, and on warm winter’s days when insects emerge, the gorse has very little competition for their attentions as it is one of the very few options on the menu.

That goes some way to answering the question of how, but it does still leave the why. Why not? isn’t really a good enough answer. This seems to have received attention from researchers only relatively recently. A group of French Researchers identified two main flowering strategies in gorse populations (as there are of course plenty of flowers to be seen in the spring and through the summer too) which seem to reflect two different ways of avoiding losing their seeds to little seed-eating weevils of the Exapion genus. One strategy is to avoid the weevil and, by flowering in the dead of winter in conditions that are too harsh for the weevil, they do just this. Winter flowering specimens tend to produce a smaller number of flowers through a long winter season, so maximising their chances of flowering through a warm spell when pollinators emerge. The other strategy is to produce so many seeds that there are many more than the weevils can consume and this is what the spring flowering shrubs do, producing very large numbers of flowers over a much shorter period. A later paper identified a genetic basis for this – that gorse seeds from a winter flowering specimen tend to produce offspring which do the same.

On a more practical note, gorse flowers can be used to make wine and winter may well be the best time to pick them if you want to do this – for the very reasons outlined above, you will spend much less time picking little black insects out of your harvest, although the flavour is less intense than spring and summer flowers! You’ll appreciate the slight reduction in workload though as gathering enough is rather a laborious process and don’t forget the gloves as being prickled by the sharp spines soon gets old. And if wine isn’t to your taste, there are lots of recipe’s for gorse cordial out there too.

As well as admiring the gorse, a wander up the hill gives you a wonderful opportunity to look down on Grantham, the skyline dominated by St Wulfrums. As the weather warms, you’ll be joined by a range of songbirds as the gorse provides a fantastic nesting site with its tangled mass of trunks and branches. And look out for a black rabbit amongst those grazing as you approach!