Morning,

Before I start, a quick clarification - this email is about Phenology, the science of nature's seasonal timing. It is not about Phrenology - the Victorian pseudoscience of reading personality from the bumps on your skull:

Image courtesy of: https://www.simplypsychology.org

I mention this only because I made the mistake of googling one when I meant the other, and spent an uncomfortable ten minutes wondering what the shape of my head says about my character. The answer, apparently, is nothing. The science was entirely made up.

Phenology, on the other hand, is very much real - and if you fish rivers or stillwaters, it's probably the most useful thing you'll read this week.

But before I get into the meat of this missive:

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(and fancy some free advertising)

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As part of the early UK launch, we’re putting together the first layer of local guide knowledge and would like to hear from Independent UK Fly Fishing Guides who may want to be included.

Selected UK guides who join during this early stage will be invited as founding guide partners (with complimentary access) as we build out the UK platform.

The aim is to create a useful source of local fly fishing intelligence, shaped by the people who know their water the best.

If you guide professionally or semi-professionally in the UK and would like to hear more (and fancy some free advertising to our 20,000 customers), just reply to this email with “guide” (or click the button below) and I’ll send you the details when we’re ready.

P.S. Not a guide yourself? If you know a good independent UK Fly Fishing Guide, feel free to forward this email to them.

I want to talk to you about hawthorn blossom - bear with me, this isn't a gardening email.

In late April, the hawthorn on the lane behind my house exploded into flower - great white drifts of it, earlier than usual, which told me something I'd half suspected since the warm weeks in early April. Spring was running ahead. The accumulated heat had been banking up since March, and the hedgerows were benefitting from it.

And then, this week, it went absolutely berserk.

On Sunday, the UK broke the May temperature record - a record that had stood since 1922 (34.8°C at Kew Gardens), then broke it again on Monday (35°C).

To put that in perspective: those are temperatures that would be unremarkable in southern Spain in August. In England. In May. The previous record had stood for 104 years, and we didn't just nudge it; we smashed through it by more than two degrees Celsius!

For most people this week, that's been sunscreen and garden chairs. For those of us who fish rivers and stillwaters, it means something rather more complicated - it's called Phenology ...

What actually is Phenology?

Phenology is the study of the timing of recurring events in nature, not by date, but by accumulated biological and environmental cues. Flowers blooming, butterflies emergence, bird migration.

When the swallows arrive. When the hawthorn flowers. When the hawthorn fly hatches at almost exactly the same moment, for reasons that are not coincidental - that's phenology in action.

The study began in Britain in 1736 - a Norfolk landowner called Robert Marsham started recording what he called his "Indications of Spring." He was doing, informally, what scientists are still doing today through the Woodland Trust's Nature's Calendar database, which now holds almost three million records spanning 300 years.

The most important thing Marsham understood - and that your hatch chart doesn't tell you - is that nature runs on accumulated warmth, not dates. A calendar is a human convenience. An insect doesn't own one.

The most compelling recent evidence for this comes not from a hawthorn hedge in Scarborough but from a Mayfly study conducted over seven years on the River Dove in the Peak District. Researchers tracked Ephemera danica - our Mayfly - at two contrasting sites on the same river, eight kilometres apart. Rather than measuring emergence dates by month, they modelled Growing Degree Days: accumulated warmth above a threshold temperature, banked up over time.

What they found was striking. Emergence tracked GDDs almost exactly. Warm years triggered early emergence. Cool years pushed it back. In the warmer upstream site, after particularly hot summers, the mayfly even shortened its aquatic larval stage from two years to one - the insect literally accelerating its own life cycle in response to accumulated heat.

Same hatch chart. Very different river reality.

What phenology tells us about right now

I talked above about degree days and accumulated warmth - the idea that nature runs on banked heat rather than calendar dates. The extraordinary temperatures this week have accelerated the seasonal clock considerably.

What that means in practical terms: the Mayfly emergence has compressed and largely passed, but the broader summer hatch sequence - pale wateries, yellow mays, blue-winged olives, the first caddis of the evening - is arriving earlier than a normal year's calendar would suggest. The river is transitioning faster than usual.

During transitions, when no single fly is dominating the surface and fish are opportunistic rather than selective, a Wulff is close to the ideal tool. It's big enough to see at distance. It floats in conditions that would sink something more finely dressed. And it covers enough of the upwinged silhouette that a fish looking up from depth will make a decision in its favour.

Our selection covers four patterns that, between them, address the major river types and light conditions across the UK:

• Grey Wulff: The original and still arguably the best post-Mayfly river pattern. Grey body, grey hackle, grey wings with brown tips. Reads as an olive or a dun in most lights. Size 12 for the riffles, size 16 when fish are clued-up.
• CdC Grey Wulff: The same silhouette, but with CdC wings rather than deer hair. Fishes beautifully in slower glides where you need the fly to sit lower and more naturally. When a standard Grey Wulff is being ignored on a flat pool, try this one before you change the pattern entirely.
• White Wulff: Cream body, cream hackle, white wings. Lee Wulff's own favourite, supposedly. Outstanding for evening fishing when you need to track the fly in fading light - it's visible long after a darker pattern has disappeared. Particularly good on those warm, clear summer evenings that the coming weeks will produce in abundance.
• McPhail Wulff: Tinsel ribbed body, grizzly hackle, dark grey wings mimicking the natural. As the Mayfly wanes, this is the pattern that bridges the gap. Fishes well throughout June on most rivers.

Wulff's also make great searching patterns and are good representations of the major up-winged flies found on the water, post-mayfly, in June, July & August. Here we have a selection of 16 Wulffs four different patterns (to cover the major fly types & colours in the UK) in two different sizes.

Here we have a selection of 16 Wullfs, four different patterns (as above) two each of sizes 12 & 16. Our Barbless Wulff Selection is now available, priced at only £24, which includes fast, free delivery to anywhere in the UK. Click on any image or button to view the flies in more detail.

A quick word on this week's conditions:

The heat has changed the fishing. You know this already if you've been out. Low, warmer, gin-clear water means fish in the shade, fish near springs and feeder streams, fish that are there but suspicious. Early morning and evening are your windows - the Wulff really comes into its own in that late afternoon through to dusk slot, which handily is also the coolest part of the day right now.

The forecast suggests temperatures easing through the weekend and into next week. When the heat breaks and conditions normalise, there will be a brief window - a day or two - when fish that have been sitting tight suddenly become active again. They'll be hungry, the river will be at a comfortable temperature, and the evening rises can be extraordinary after a hot spell breaks.

Have the right flies in your box before that happens, not after!

--- Go on, you know you want to ---

Lee Wulff was one of those rare people who managed to be right about almost everything. He invented the fishing vest, pioneered catch and release in the 1930s when it was considered eccentric bordering on suspicious, and tied a series of flies that bore his name and have outlasted just about everything else from that era.

"The story starts almost 70 years ago. Almost all dry flies available in the winter of 1929/30 were, according to Lee Wulff, anaemic and too delicate, which he ascribed to their British tradition and heritage. The reason for very slim flies was that if a fly was too bulky the feather materials did not have the buoyancy to hold it up. A very popular pattern, for example, was the Fanwing Coachman that not only twisted the leader but also sunk at the tail due to the golden pheasant tail fibres used. Wulff also noted that dry flies with wings and tails of feathers get slimed up and are not very durable. To Wulff, the solution was obvious---use bucktail for tails and wings. The first Wulff flies were tied to imitate the Isonychia (Gray Drake) and Green Drake hatches in the Catskills.

Wulff first fished these patterns with his regular fishing companion, Dan Bailey, who was then a science teacher in Brooklyn. In those early trials with these new patterns, Lee's was not disappointed. He found that the fish seemed to prefer the bulkier flies that 'looked more' like the naturals than the more anaemic patterns then popular. With respect to durability, the hair-wing flies also excelled.

Wulff reports he caught 51 trout on one Gray Wulff fly in an early outing, needing only to "grease up the fly for every 5-6 fish". The first patterns he designed included the Grey Wulff and White Wulff"; Federation of Fly Fishers (fedflyfishers.org)

The Wulff dry fly, as first tied by Lee Wulff, with its bushy hackle is a great fly for those riffles which would sink a more delicate fly. The 'Wulff style' of flies come into their own in the afternoon through into late evenings.

When searching the river with a Wulff, try this technique:

1. From the bank, section the river into lanes about 3ft wide.
2. Cast upstream and make 3 or 4 drifts in the nearest lane, repeat for each lane, working away from you.
3. Retrace your steps back to the bank; and
4. Step upstream and repeat the process.

Practical Phenology?

These aren't folk tales. They're biological indicators that have been tracked in the UK for the better part of three centuries:

• Hawthorn already browning at the edges - The blossom came and is going. That tells you where you are in the seasonal calendar more accurately than the date on your phone. You're in late-May phenological territory regardless of what the thermometer was doing a fortnight ago.
• Swallows working low over the water - Swallows don't turn up to find nothing. If they're hunting just above the surface, the aerial insect biomass has climbed sharply. That's a hatch signal you can read from the bank before you've tied on a fly.
• Fish bulging rather than rising cleanly - A bulging rise - that slow, confident swirl just below the surface - means fish taking emerging nymphs in the film. The main event is close, possibly already underway. The splashy, aggressive rise you're looking for in a full mayfly hatch may follow within the hour.
• Evening spinner falls arriving earlier than expected - In high temperatures, the daytime hatch can be suppressed - the heat compresses the window, insects emerge faster, trout may be more cautious in bright, warm, low-clear water. But the spinner fall in the cooler evening air? That's where this week's fishing may really reward the angler who shows up and pays attention.

Tight lines & have some phenological fun out there.