Growing up, I spent two weeks with my dad every summer in the Gunnison Valley, fishing small creeks, untamed freestones, and the world-class tailwater below Taylor Park Reservoir. The highlight of our summer vacation was the arrival of the fabled Green Drake hatch that begins in late June and continues through the first part of August. Some of my most memorable days onstream with my father were on the Taylor River a few miles upstream from the small community of Almont.
If you’ve experienced a Green Drake hatch, then you know exactly what I am talking about. The thrill and excitement of a multi-day road trip during the Green Drake hatch is as good as it gets. Some of my favorite locations in Colorado include the Gunnison, East, and Taylor rivers, as well as the Roaring Fork and Fryingpan rivers. The Eagle, Blue, and Yampa rivers are good options too.
While my experience is based mostly in Colorado, these mayflies are widespread across the West wherever there is fast, rocky water free of silt and pollutants. In Wyoming, the upper North Platte and Encampment rivers have incredible hatches. In Idaho, the Green Drake hatch is the most important seasonal event on the Henry’s Fork, and the story is much the same on tumbling, highly oxygenated rivers in and around Yellowstone National Park, on many Montana rivers, and throughout the Pacific Northwest.
Timing the Hatch
Being in the right place at the right time is critical for success. Otherwise you may experience only sporadic Drakes, or miss the hatch entirely, and wonder what all the hype is about. Drakes start hatching as early as June 15 at lower elevations and last through the month of July in cold, high-elevation streams. Depending on snowpack and weather, the first week of July is usually a good time to find these insects somewhere on watersheds with good populations of Green Drakes.
Green Drake emergences often progress upstream a little each day, starting in the warmer lower elevations of a river and working slowly into the headwaters. Targeting the heaviest concentration of the hatch is often one of the biggest challenges. It’s a good idea to check with a local fly shop or guide service for up-to-date information on the exact location of the hatch.
Water temperatures, river levels (from spring runoff and downstream irrigation demand), and weather patterns can affect the speed at which the hatch travels upriver. For instance, if the water is low from a lean snowpack, the hatch starts earlier in June, and moves upriver quickly because the river is warmer, which accelerates the development of the mayflies. To the contrary, if flows are above normal levels due to a heavy snowpack, the hatch is delayed a week or two due to cooler water temperatures.
For walk-and-wade anglers, the hatch is straightforward—show up in the right location about noon in anticipation of the duns coming off around 1 P.M. Prior to the hatch, I recommend nymphing the faster riffles and runs with a Green Drake nymph imitation, or swinging a soft-hackle in the transitional zones.
Floating the river with an inflatable raft or drift boat is more complex. The best advice I can give is to launch your boat several miles above the hatch, making an effort to stay upstream from the peak of the hatch. The hours leading up to the hatch are a good time to fish with a size 12 Parachute Adams trailed by a size 14 Elk-hair Caddis, methodically pounding the banks, looking for opportunistic feeders.
Don’t rule out seeing Pale Morning Duns or Yellow Sallies, as these hatches tend to overlap each other during the first two weeks of July. If you see trout eating these other insects, make the appropriate fly changes. If you’re not getting the results you hoped for with dry flies, try nymphing with a #10-12 Hare’s-ear trailed by a size 16 beadhead Flashback Pheasant Tail or a size 16 PMD Barr Emerger.
I routinely take an early lunch on the leading edge of the hatch and carefully watch the water for emerging duns. Once I begin seeing large olive mayflies on the water, I move downriver and look for rising trout. Green Drake hatches tend to last for an hour or two depending on the weather.
Drakes bring up some of the biggest and wariest trout to feed on the surface. Don’t be surprised if a 20-inch rainbow gobbles your Green Drake.
Green Drakes tend to be a late morning or an early afternoon event, but they are highly weather dependent. The best hatches occur on overcast or rainy days because the high humidity tends to delay the development of the duns, keeping the naturals on the water longer. Bright and sunny days accelerate the hatch, and the duns escape more quickly.
One of the best Green Drake hatches I’ve ever experienced was on the Taylor River, one mile above Almont. Afternoon rain showers are a common occurrence in the Taylor Canyon, and this day was no different. My buddy and I showed up to the river and it began sprinkling. The skies were dark up in the canyon, so we knew what was heading our way. We put on our rain jackets and headed to the river and immediately starting hooking trout that were feeding on Green Drakes in 18 to 24 inches of riffle water.
Within 15 minutes the skies opened up and it began pouring.
Strange as it might sound, the harder it rained, the more the Green Drakes came off! At one point, there were two dozen trout feeding on the surface within my casting range—one of the most amazing sights I have ever seen.
There are two species of Western Green Drakes: Drunella grandis and Drunella doddsii. Don’t confuse them with the mayflies called Green Drakes in the East (Ephemera guttulata)—those are completely different larger, burrowing mayflies.
Drunella grandis and Drunella doddsii duns look similar, although the latter is slightly smaller. They are both Western Green Drakes, and it’s not uncommon to find both species in the same river, so carry several different sizes (#10-14) of Green Drake imitations to match the hatch.
Green Drake nymphs are crawlers and thrive in large cobbled substrates with moderate to fast-paced currents. Green Drake nymphs are easily identified by their robust stature and rugged appearance. Their large size differentiates them from other mayflies, as mature nymphs are almost an inch long.
Green Drake nymphs are dark olive, with three tails, stout abdomens, thick boxlike thoraxes, and squared-off heads with prominent eyes. My favorite imitations are #10-12 olive or natural beadhead Hare’s-ears, Stalcup’s Green Drake, Barr’s Tung Teaser, or Mercer’s Green Drake Poxyback Nymphs.
Prior to emergence, mature nymphs migrate toward slower riffles and runs where their availability to the trout increases exponentially because they are poor swimmers. They frequently become victims of catastrophic drift and become hearty meals for opportunistic trout.
Their emergence begins underwater, then the crumpled-up dun floats to the surface to dry its wings and take flight. Soft-hackles and emerger patterns fished on the swing or near the surface are deadly for imitating these rising duns. Because of their large size, Green Drakes take much longer to dry their wings and escape the surface in comparison to smaller mayflies.
When a hatch starts, I clip off my Green Drake nymph and switch to a size 12 Mathews’s Sparkle Dun, Cannon’s Snowshoe Dun, or a Parachute Green Drake. Low-riding patterns work best most of the time, but on occasion a standard hackled fly performs better than a parachute or Compara-dun. I recommend fishing with one of each type to cover your bases. I also recommend carrying a few spinners, as in some watersheds they are extremely important just before dark.
Trout eating Green Drakes produce splashy rise forms, which can mislead fly fishers into thinking they are eating fluttering insects like caddisflies or Yellow Sallies. Careful observation removes any doubt about what the trout are feeding on. Watch the naturals and pay close attention to what the trout are actually consuming. As previously mentioned, it’s entirely possible to have caddis, Yellow Sallies, and Pale Morning Duns hatching at the same time.
Green Drakes often skitter on the surface a bit before taking flight, which induces aggressive takes. I find a traditional hackled fly works better when the trout are keying on Green Drakes struggling to get off the water’s surface like this. Compara-duns and Parachutes perform better on warm sunny days when the duns take flight quickly. A standard hackled fly portrays movement better than a low-rider sitting flush on the water’s surface.
Steve Henderson, a 25-year veteran guide and owner of Henderson Fly Fishing in Steamboat Springs, swears by a Hare’s-ear for imitating Green Drake nymphs. Try seining the Yampa River and you’ll see why—the substrate is loaded with Green Drake nymphs, and the fish are always aware of their presence, regardless of the time of year.
“The Hare’s-ear is an extremely versatile fly. It is my go-to nymph for imitating Green Drake nymphs. Green Drake nymphs are crawler mayflies. They have oversized legs for holding onto and crawling around rocks in the faster parts of our Western rivers. The thorax sections of the nymphs are large and wide in comparison to the abdomen. I tie my Hare’s-ears with a buggy thorax section with plenty of guard hairs picked out. The abdomen section is dubbed tighter to represent the slimmer section of the naturals. The finished fly should have a similar proportion to a body builder; wide shoulders tapering down to their feet,” says Henderson.
“My favorite colors are natural, black, and olive in that order. Effective sizes are #10-14. I forgo the Mylar tinsel (gold rib) in favor of copper wire. This gives the fly a more natural look and makes it extremely durable. I am particularly fond of adding a copper tungsten bead to my Hare’s-ears.”
Henderson typically uses a #10-12 Parachute Adams or Parachute Green Drake for imitating newly hatched duns. “I find Parachutes work most of the time, but if the trout get picky, I use a deerhair extended-body Green Drake pattern. I clip the hackle to ride flush on the surface, and the wing angles slightly forward. The fly lands on its feet 99 times out of 100 and fools extremely selective trout.”
Will Sands, a guide and manager at Taylor Creek Fly Shop, is a true authority on Green Drake hatches. The shop is near the junction of the Roaring Fork and Fryingpan, and both rivers are known for their legendary dry-fly fishing during the Green Drake hatch. Sands recommends a Mercer’s Poxyback Green Drake Nymph or KGB (Killer Green Bug) for the Fryingpan. “I like technical ties for discriminating tailwater trout. A freestone like the Roaring Fork is a different story—without any question my favorite fly there is a 20 Incher. Although it was originally tied to emulate a stonefly, its profile is truly drakelike.”
When Green Drake nymphs begin to emerge into duns, Sands is a huge fan of Umpqua’s Mayfly Cripples, and offers this advice: “Grease or powder the deer-hair head, and do not dress the marabou abdomen. This positions the fly half above and half below the surface, which is deadly tactic for selective fish.”
As far as dry flies are concerned, Sands uses a custom-tied Sparkle Dun because the coloration of the Green Drakes on the Fryingpan is dark gray wings with a dusty olive/gray abdomen. Many anglers believe they are seeing Gray Drakes, when they are actually Green Drakes. “We recommend our Taylor Creek Custom Sparkle Dun (the dubbing color was created specifically for the Fryingpan). It has a Sparkle Dun profile, tied sparse, which is essential for technical waters.”
On the Roaring Fork, Sands suggests an H&L Variant or Furimsky’s BDE (Best Dry Ever) Green Drake. “These patterns are high-floating with a robust profile that works well in rougher waters where exact color is not necessary. They are visible bugs that can support a nymph or help detect strikes on other flies that are harder to see in choppy water.”
Sands also encourages fly fishers to carry plenty of spentwing imitations. The spinner fall occurs just before dark and provides anglers with technical and rewarding dry-fly fishing. “Grease the wings on Stalcup’s Emerger, then pull and twist the wings out spinner style. This is the best spinner pattern I’ve found.”
Jason Booth, co-owner of Gunnison River Guides, is one of the most respected guides in Colorado. Each season he anxiously awaits the beginning of the Green Drake hatch because it provides some of the best fishing of the summer. “Green Drakes are the largest Western mayflies. When they hatch, every fish in the river keys on them,” says Booth. “The best time to fish Green Drakes on the Gunnison is late June to July 10. On overcast, windless days the hatches last for a couple hours. The hatch usually reaches the Taylor River the first week of July. Here it slows because of the cool, consistent water temperatures, which provides great fishing the whole month of July.”
Booth’s favorite Green Drake nymphs are #10-12 Mercer’s Green Drake Poxyback, Stalcup’s Green Drake, and 20 Inchers. “Drake nymphs are deadly in soft water margins, especially in the transitional zones that funnel into some of the deeper runs,” says Booth.
Once trout commit to eating the duns, Booth’s favorite dry flies are CDC Parachute Green Drakes, Mayfly Cripples, Furimsky’s Foam Green Drakes, Colorado Hen Wing Green Drakes, and CDC Flavilinea Duns. He typically fishes with a tandem rig, mixing and matching to find which pattern is working best.
Tackle & Presentations
I recommend using a 9-foot 5-weight rod for nymphing, and a 9-foot 6-weight for dry-fly fishing, especially in the wind. During the height of a Green Drake hatch, I routinely fish with two dry flies, so a heavier and stiffer rod helps with precise deliveries.
I typically use a 9-foot 4X tapered leader, then add 18 to 24 inches of 4X tippet material. If I am fishing out of a drift boat or raft, I rig up multiple rods to reduce downtime and be prepared for multiple simultaneous hatches. On one rod I’ll have a size 12 Sparkle Dun trailed by a size 12 Quill Gordon, and on another a size 12 Parachute Adams trailed by a smaller offering like a PMD or Elk-hair Caddis. When wading, it’s difficult to carry multiple rods, but there is also plenty of time to change rigs in comparison to drift fishing, when you’re on the move and have little or no time to make changes.
Once I locate a rising fish, I prefer a downstream delivery so the first thing the trout sees in your fly, not the tippet, leader, or fly line. Upstream presentations can put the fish down, so I try to avoid them. To reduce cross-current drag, I use a reach mend and add some slack to assist in a dead drift. It’s important to let the trout come up and eat your fly, then allow the trout to dip its head below the surface before setting the hook, otherwise you may be premature.
One of the biggest mistakes I see is anglers casting their flies too far above their targets. The farther you cast your flies ahead of a rising trout, the greater the chances of drag occurring. Drop your fly just 24 inches above the rising fish and make the appropriate mend.
It’s important to keep your dry flies dressed properly to keep them floating. I start with a paste floatant, then use powder or crystals when the fly becomes waterlogged or a trout has eaten the fly. I am a huge fan of Shimazaki Dry-Shake. Simply drop your fly (with the tippet attached) into the container, close the lid, and shake. Your fly is instantly ready to get back on the water.
With CDC or Snowshoe patterns, do not use paste floatant. I recommend Frog’s Fanny. It’s perfect for delicate dry flies, especially CDC. The handy applicator brush allows you massage the dry-fly powder into the wing to keep your fly floating.
If you haven’t had the opportunity to experience a Green Drake hatch, you’re missing out. Hopefully this gets you all fired up and ready to come see it for yourself.
*Pat Dorsey is a co-owner of Blue Quill Angler and has been a guide on the South Platte River for more than 25 years. His most recent book is Fly Fishing Guide to the South Platte River (Stackpole Books, 2019).