A celebration of frost

This has been an unusually mild winter in the Highlands of Scotland so far, with very little snow having fallen and temperatures consistently being well above zero (and often as high as 10 degrees C) on most days. There’s also been surprisingly little rain, and although the hours of daylight are very short, it feels as though winter hasn’t really arrived yet. Perhaps this will be a repeat of the last two or three years, when the coldest weather and most snow has been in March or even April, rather than the more usual months of January and February.

I suspect these skewed seasons, with the winter weather delayed by one or two months, may be a manifestation of climate change caused by the build up of carbon dioxide in the atmosphere from our burning of fossil fuels. Whatever the cause, I’m missing the beautiful snowy landscapes of ‘real winters’ and am still hoping we’ll get some days like that in the coming weeks. In the interim though I’ve been enjoying another manifestation of this season – the hard frosts that appear after cold, cloudless nights with sub-zero temperatures.

I’ve long been fascinated by the visual beauty of the shapes and patterns that frost makes, and the ephemeral nature of these miniature crystalline landscapes adds to their mystique for me. I’ve compiled a significant collection of photographs of them over the years, and, stimulated by a few recent very frosty days, this blog provides an opportunity for me to share some of them.

 

 

 

 

 

 

 

 

 

 

 

 

 

From the knowledge of Glen Affric that I’ve built up over the past 40 years or so I know where many of the coldest spots are – the real frost pockets in the forest. They are typically located just to the north of steep slopes that reach to higher ground, meaning that they rarely (or in some cases never) receive direct sunshine in the depths of winter. The constant shadow keeps the temperatures low there, and it is to those places that I head for on cold frosty mornings.

One such place is at Dog Falls, where the high rocky cliffs that create the Affric River gorge (and thereby give rise to the falls themselves) rise abruptly up on the south side of the river. In late October and again in mid-November I spent the best part of two days there, exploring the fabulous frost formations that had resulted from several days of constant sub-zero temperatures.

It is this consistency of freezing conditions over a period of several days which leads to the growth of the most dramatic frost formations. Fallen leaves, the twigs of trees and sprigs of heather (Calluna vulgaris) were all coated with beautiful crystalline creations then. In some cases the angular fringes of frost completely encased the plant or leaf they had formed on, making it difficult to see what was underneath the accumulation of ice shapes.

As the frost continues to ‘grow’ when the temperature remains below zero, the crystals often develop the form of needles extending outwards from where they have originated, as in the case of these leaves of a cowberry plant (Vaccinium vitis-idaea) shown here. Over a period of several days these needles can reach a size of 5 mm or more, and look like some sort of miniature ice construction project, lined up next to each other.

I spent a few minutes studying the frost needles on these cowberry plants, and my attention was drawn to one where the leaves were bright red. Unlike its close relative, the deciduous blaeberry (Vaccinium myrtillus), cowberry is evergreen, and each plant keeps the majority of its leaves through the winter. However, as with all evergreen plants and conifers, some leaves do get shed when they have reached the end of their usefulness for photosynthesis, and the bright colours of these ones seemed to be accentuated by the frost needles that decorated them.

As usual, I was finding that when I spent some time looking closely at details such as the frost on these leaves, I began to notice other small and equally fascinating features all around. In this case it was the frosted web of a spider that caught my eye in amongst some grass on the ground. From its position and construction, it looked to me to be the work of a money spider (Linyphia triangularis), which spins a horizontal sheet web, but there was no way of knowing for certain without seeing the spider itself.

The crystalline shape of the frost was clearly visible on the web, but later in the day I came across another web, probably made by the same species of spider, where the frozen shapes were much more rounded. These looked to me like they were water drops that had frozen, keeping their shapes as they did so, whereas the frost develops its distinctive crystalline forms without there being liquid water present beforehand.

When the temperature gets very low and remains that way for days on end, some truly spectacular frost formations can develop. During the two very cold winters that we had in Scotland in 2009 and 2010, I was able to photograph some of these, in Glenmoriston and at Trees for Life’s Dundreggan Conservation Estate. Remarkable feather-like frost shapes sprouted out from plant stems, seeming to make icy impersonations of the wings of birds, frozen in time for a few short days while the cold spell lasted.

The stems of some plants that were protruding out of the water in small ponds gained various crystalline branches, giving them the appearance of angular white flowers that wouldn’t look out of place in a science fiction film about an alien planet.

 

 

 

 

 

 

 

While the miniature details of the frost on individual plants are a constant source of beauty and wonder, the panorama of large expanses of trees bedecked in shimmering white crystals is equally spectacular. This is especially the case for a short period in the mornings after a night of hard frost, when the early sunshine illuminates everything for a short period. It’s a question of being there at exactly the right time, before the heat of the ascending sun, or the arrival of a breeze, begins to melt the white crystalline clothing of the trees.

I experienced a morning like that in Glen Affric a couple of years ago, in January 2017. The vista over the forest beside Loch Beinn a’ Mheadhoin created one of the most beautiful and impressive landscapes I’ve ever seen. Every branch and twig of all the birches (Betula spp.) was coated in frost, forming an immense and delicate white filigree effect that shone with an inner radiance. It was almost as though I was seeing the inner life force of the trees somehow made visible externally for the first time.

Slightly further west, the birch trees are interspersed amongst some of the old Scots pines (Pinus sylvestris) that Glen Affric is best known for. Their darker shapes broke up the massed white of the frosted birches in what to me was a very visually appealing way. The pines had frost on them as well, but it was much less obvious, appearing as just a lighter tinge on the edge of their green canopies. Whereas the birches seemed to positively glow with their white coating, the pines were much more subtle in displaying their frosted foliage.

I’d stopped at Dog Falls that morning, and the forest had been in complete shadow there. The more even light (due to the absence of bright direct sun on the trees) meant that the frost on the pines was more visible, although it still wasn’t as dramatic as that on the birches. The stillness and silence of the early morning landscape was palpable, and somehow it made me think about how many mornings like this the trees there must have experienced since the forest returned to Glen Affric after the end of the last Ice Age.

 

 

 

 

 

 

 

There were countless opportunities for photography that morning, but they were all very temporary. The interplay of low-angled sun and deep shade produced some high contrast compositions, but it was a question of seizing the moment quickly, before the sun melted the frost.

It’s harder to photograph frost close up on a Scots pine than it is on a broadleaved tree such as a birch, because of the three dimensional pattern of growth of the pine’s needles. At the close distances needed to see the frost in detail it’s difficult to have enough depth of field to keep the needles fully in focus. I find it requires a lot of patience to achieve a reasonable result, but recently I’ve had some success, mainly by concentrating on younger pines, where the needles are at a more accessible height.

Frost can transform anything in Nature into crystalline creations of stunning  beauty, and even the dried and dead remnants of annual or perennial plants can become ephemeral works of art. One morning at the end of October I spotted the umbel or seed head of an angelica plant (Angelica sylvestris) near the Affric River that was covered in frost. However, it was also just about to be illuminated by the rising sun, so I had to be quick to get some images of its chandelier-like crystal-clad shape. A few minutes later all the frost was melted by the sun, and in a Cinderella-like fashion the angelica’s brief period of great beauty had been replaced by its more mundane ‘end of season’ appearance.

During my day in Glen Affric in mid-November I came across some frost in shapes and patterns that I’d not seen there before.

 

 

 

 

 

 

 

Whereas the frost usually takes on linear crystalline forms, on this day it had developed in a pattern of flower-like shapes that resembled the shells of scallops in the sea. This was particularly obvious on some fallen leaves of a goat willow (Salix caprea), although they can also be seen on the edges of the birch leaf in the photo above. The more I looked, the more of this pattern of frost there was, and close examination revealed what I can only describe as a spectacularly beautiful miniature landscape of organic ice shapes.

 

 

 

 

 

 

 

 

 

I’ve searched on the Internet to see if I could find any information about these shapes, without success so far. Perhaps it’s a combination of factors, (eg ambient temperature, moisture content of the air etc), that enables the frost to develop in this way?

Interestingly enough, the day before I found these unusual frost shapes in Glen Affric, I’d seen some similar ones near my home at Findhorn. There, they were on fallen birch and oak leaves, and the formations also looked like miniature scallops. There had been several days of sub-zero temperatures across all of northern Scotland, so the similar conditions at both Findhorn and Glen Affric must have been conducive for the growth of the frost in these shapes.

The day after my visit to Affric in mid-November, the temperature rose again and I’m guessing all the frost disappeared, leaving behind just memories and photos of its spectacular beauty. I wonder when I’ll see such formations again?

 

 

 

 

 

 

 

I suspect they may be quite rare, but I’ll be keeping a look-out for them whenever there’s a prolonged period of sub-zero temperatures. The next period of hard frosts occurred in early December, and although I didn’t get out to Glen Affric then, I did spend some time out in the dunes at Findhorn then. There was a lot of frost in shaded locations amongst the dunes, and I took these photos here, of lichens and a tiny fungus that were all covered by the more usual linear structures of frost crystals. Whatever conditions had enabled the other scallop-shaped frost to manifest previously had not been repeated this time, so I suspect the causal factors will remain a mystery to me, at least for the time being.

I’ll finish this blog with some more photos taken in Glen Affric during a couple of those very frosty days in November. These are not strictly of frost however, although they look like frost at a casual glance.

 

 

 

 

 

 

 

Instead, they are of hair ice, a remarkable phenomenon that I wrote about in a blog three years ago, in January 2016. The presence of a fungus (Exidiopsis effusa) in dead wood apparently facilitates the extrusion of these very thin filaments of ice into the parallel curled shapes that are sprouting from some fallen branches of a rowan (Sorbus aucuparia).

In 2016 I’d come across these beautiful ice formations for the first time in some native woodland at Inverfarigaig, on the east side of Loch Ness. It was therefore very satisfying to find them in Glen Affric in mid-November. As sometimes happens though, after never having seen them in Affric before, a week later on my next trip to the glen, I came across some more! This time they were on a dead birch branch, and the hair ice was also coated with a layer of frost crystals, giving a remarkable juxtaposition of two different phenomena caused by sub-zero temperatures on the same branch.

I’m still waiting for the snow to arrive in significant quantities this winter, but in the meantime I’ll continue to appreciate and document the breathtaking beauty and diverse shapes of frost …