Published Apr 11. 2012 - 11 years ago
Updated or edited Oct 12. 2023

A New Look at the Grannom

The Grannom is a small sedge (caddis to those in USA), which hatches in large quantities in April and is regarded as the first fly to prompt trout to "look up".

The Grannom - A sedge or caddis with a bright, green body
The Grannom
Trevor Morgan

The Grannom is a small sedge (caddis to those in USA), which hatches in large quantities in April and is regarded as the first fly to prompt trout to "look up".

The hatch lasts for a few hours, mostly in the morning and usually for 2 weeks in April.

I have, like most fly fishers, used the traditional patterns with a brown body, or one with peacock herl, brown wing and brown hackle, 0n a size 14 or 16 hook.

It caught trout, but in my experience I only had one offer from every ten presentations to trout, which were feeding regularly. I do not wish to catch a trout every cast, but this made me wonder why this type of standard pattern only received a few responses.

My research into the life cycle of the Grannom revealed that in the pupa or nymph stage, the body is green and segmented with thin black bands. On emerging the body remains the same colour, and, only after it has been in flight does the body change to a brown and wings become dark brown. So, perhaps we, as fly fishers, caught a few Grannom specimens to imitate, and these would have had the brown body and dark brown wings, whereas the trout were taking eagerly the emerging fly with the green body! So, I came up with this new pattern.

Early spring - The Grannom hatches right as the trees start getting leaves in April
A brown trout fell - The early grannom hatch make the brownies look up towards the surface
Grannom water
Trevor Morgan
The Grannom
Pattern type: 
Dry fly
Trevor Morgan
size 14 or 16
Black 8/0
black tying silk well waxed and doubled to make it thicker
green seals fur (green highlander as used in salmon flies is fine)
3-4 plumes of dark CDC trimmed so that it is no longer than the bend of the hook
3-4 turns of red game genetic cock, wound in front of the wing
Skill level/difficulty: 

So did this new fly work? All I can say is that on the chalk stream where I fish - the river Avon in Wiltshire, England, on the first trial, 3 of us caught 17 brown trout. It has proved itself consistently ever since then.
Since the Grannom "season" is only a short two weeks, perhaps this fly could be a welcome suggestion to make the most of your fishing. I am not there to rewrite fly fishing books, but, like those who contribute to this web site, share our experiences in the hope that others can achieve the same enjoyment success.


Thanks for sharing t...

Thanks for sharing this very inspiring web page. I've spent the last three or four years trying to find the right Grannom pattern to no avail, and found the mainstream UK pre-tied market lacking for this particular hatch. I have bitten the bullet and taken up fly tying and this seems like a very good starting point...

The Grannom hatches ...

The Grannom hatches on parts of the Avon last April really had to be seen to be believed. Trout were gorging themselves, picking the flies off weed and obstructions even in the fastest water, as well as off the top. They were interested in little else except the occasional olive and hawthorn.

Peter Laurie


In the US at least, there are at least 4 species that are of importance to trout. They often appear on the same streams (Americanus,numerosus,appalachia and occidentalis) and most species can be found across the country. These are one of the first major caddis hatches of the year in some areas (most Grannom activity is from mid-April to mid-May). There can be overlap of species hatching and the colors and sizes vary between species (males are typically 1 to 2 sizes smaller than females). Body colors on adults range from green to greenish brown to brownish black or grey. Grannoms give you all day fishing. Starting with larva/pupas in the morning, emergers around 10 am, adults dry on the surface mid-morning til noon, soft hackles for drowned adults through the day, then a return in the late afternoon/early evening of the skittering, oviposting adults and then finally spent flies at dark. Just an FYI from across the pond ;)


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