Because of having been away on the Millionth Tree Lecture Tour, it had been 4 weeks since my last visit to the Caledonian Forest (and 5 weeks since I’d last been at Dundreggan). I was therefore very keen to get out to the forest again, to see all the new life of spring, so about 36 hours after I got back from England, I headed out to Dundreggan for the day. It was a warm, mostly sunny day when I got there, but I was surprised to see that the birches and other broadleaved trees hadn’t got their new leaves yet.
When I’d been out in Glen Strathfarrar at the beginning of April, just before setting out on the tour, the first leaves of the birches had just been opening out, but it seemed as though spring had been completely stalled while I’d been away. I heard that it had been quite cold while I was down south, so the result was that the spring which had seemed to be unfolding very early because of the mild weather we had in late March, had in fact become later than usual. The birches normally have their new leaves fully open by the third week in April.
Although the trees were late in getting their leaves, there were other signs of spring, and one of the first I noticed was a bright orange fungus (Gymnosporangium clavariiforme) that fruits on the stems of the junipers (Juniperus communis) at Dundreggan in April each year. Steve, our Operations Manager there, had told me the fungus had been spectacular a couple of weeks previously, but it was now past its peak of fruiting. There were still some examples of it around, but they were rather shrivelled because of the warm, dry weather. The best time to see this fungus is on a wet day, when it is fully hydrated and brilliant in its colour. The species is also of note because it grows on two different host trees, fruiting first on juniper in the spring. The spores that are released then infect hawthorn trees (Crataegus monogyna), where it fruits on the leaves in a completely different form in late summer. The spores that are released then re-infect juniper and it fruits on that again the following spring. It’s quite remarkable that it should utilise two completely different tree species as its hosts, and as far as I know the ecological advantages of this are not understood.
On the forest floor there was an abundance of spring flowers in some places, particularly primroses (Primula vulgaris). I had first seen a primrose flowering at Dundreggan this year on the 25th February – exceptionally early – and I had expected therefore that they would be finished flowering about a month later. However, because of the stalled spring, they were at about the peak of flowering now at the end of April, two months after the first one had been out.
I went to look at a red-flowered patch of primroses that I’ve seen there in previous years.
There is some unclarity over whether this colour of wild primroses is a natural variation in the population, or whether they are the result of garden escapes. I’ve seen primroses with this colour in the wild in forests in the Alborz Mountains of northern Iran, and there is apparently a pink-flowered form occurring naturally in Wales, but whatever their origin, I always appreciate them when I see them, contrasting with the regular yellow primroses.
Scattered throughout the woodland were smaller groups of wood anemones (Anemone nemorosa). Like the primroses, they are early spring flowering plants, and take advantage of the opportunity to blossom between when the sun is higher in the sky from March onwards until the new leaves of the birches open out in the second half of April, at which time the amount of light reaching the forest floor is substantially reduced.
On one of the birch trees I noticed an unusual pattern of black fungus-like growth on a burl sticking out from the side of the tree’s trunk. I’d never come across anything quite like this before, and I saw that some of the black fibrous-like material had fallen and accumulated on the ground at the base of the tree. I collected some of this to send off to Liz Holden, a mycologist who helps me with the identification of fungi, to see if she can come up with any suggestions for what it might be.
On one of the visitor footpaths we’ve established nearby I came across another fungus, growing on the gravel surface of the path itself. This was a cup fungus, and it was fruiting right next to one of the benches we’ve put on the path. I’d seen this fungus fruiting in the same place last autumn, and was quite surprised to see it again now, as fungi that fruit in the autumn don’t normally fruit in the spring as well. This is another question for Liz, as it occurs to me that it may not be the same species, but in fact a closely related one – I’ve sent her some samples, so it will be interesting to see what name she comes back with for it.
Moving on a bit further, I saw a birch tree that had its new leaves opening out, in contrast to most of the other birches, which were still completely bare. I went up to it to have a close look at the leaves that were still unfurling, delicate and beautiful in their newness. I was surprised to find that they were covered with masses of aphids, both winged adults and smaller nymphs.
In fact there were aphids everywhere, and when I put my camera bag down on the ground, it soon had about a dozen winged adults crawling around on it. Every leaf that I could reach on the tree had aphids feeding on it – it seemed as though there was a veritable population explosion of aphids there. I sent some samples off to Ed Baker, an aphid specialist in Wales (who’s coming up to Dundreggan to do a survey for aphids in June this year), and he identified them as being a common species (Euceraphis punctipennis) that occurs on birch, especially downy birch.
He said that there’s also a lot of them out on the birches in Wales just now, and we had a brief exchange of thoughts about the reasons for this, wondering if the large numbers are due to the mild winter followed by the warm weather in March providing ideal conditions for their numbers to increase dramatically. It will be interesting to see if all these aphids have any significant effect on the health of the birches during the growing season this year. In any event, this abundance of aphids has reinforced my increasing fascination with them, and I’m looking forward to Ed’s visit in June, when I hope to learn more about this remarkable group of insects.