Oh man, what an epic camping spot. Getting here is a doozy, but it is so worth it.
In early September, myself, my brother, and our two cousins decided it was time for a long-overdue reunion, and getting lost in the back-country was going to be the stage for it. We struck out from Bozeman, drove as far as we could go (past Lower Seymour Lake) and then once we hit the end of the road, strapped on our (very heavy - remind me not to bring so much food next time) packs and trekked in.
The trek is pretty damn tough if you aim to do it in one go, like we did. It's about 7 miles to Upper Seymour Lake (also very beautiful, and with dispersed camping), which isn't too strenuous, but then you have to cut over a pass to get to Flower Lake. That is pretty much straight up and straight down, switchbacks the entire way. I was struggling. The views from the top are amazing though. Also, don't mistake Page Lake for Flower Lake - once you descend the other side of the pass, you'll hit Page Lake before you hit Flower Lake. Page Lake is also beautiful and has dispersed sites, but keep going. I think you'll find it is worth it.
Once we got to Flower Lake, it was serene. From the time we left Upper Seymour Lake to the time we got back, we didn't see or hear another soul. Five days of just us. The area around the lake is pretty dramatic - it sits in a little valley basically surrounded by steep mountains. Around the lake there are a few areas with rough dispersed sites. Fire pits, a few logs to make "benches", that's about it. Plenty of space to throw tents down, and TONS of firewood from the dead trees in the area. You can camp out in the open if that's your jam, or in trees. We chose the trees for better cover and because that's where we found the best dispersed site. Flower Lake itself is beautiful but absolutely frigid, so we didn't go in. There is a little stream that feeds it where we gathered our water to filter, and I finally decided to take a half-bath. Good god it was freezing, but it felt good once it was over.
Definitely check the weather before going in. We got slammed with a blizzard that lasted all of the second day and night. We were expecting snow that day, but this was more than we were imagining. It was COLD. Intense wind. Lots and lots of snow. We didn't leave the campfire the entire time except to dig out our tents when the snow got too high around them. Given we were running three-season tents, that night was bitter cold (the water bottle in my tent next to me was frozen the next morning) but we all tossed and turned and made it through it. Not gonna lie, the blizzard was a bit unnerving when we were in it, but it made the next four days of sun so much more appreciated. If you're in the sun, it's actually pretty warm, and a lot of the snow was gone a few days after it fell.
Lots of great hiking here, as the CDT (Continental Divide Trail) goes through this area. I recommend the hike to the top of Rainbow Mountain for some truly stunning views. Not too hard either, once you've cleared the initial pass to get in, and you're not carrying your full pack.
BRING BEAR SPRAY. HANG YOUR FOOD. This is grizzly country and we saw a LOT of signs of them. Fresh droppings. Fresh prints in the snow after the blizzard. We never ran into one directly, but they were definitely around. Be in the habit of making noise so as not to surprise them. I can't possibly imagine how many times I yelled "Hey bear!" over the course of the trip. We noticed that one side of the lake had far more signs of bears than where we were. We avoided it, and I wouldn't recommend camping there. See my photos to get an idea of where.
The hike out was not a cakewalk either, but with lighter packs and having the hard ascent and descent happen at the beginning rather than the end, it wasn't half as bad as going in.
This is a great spot for back-country aficionados. It was my first real pack-in back-country camping trip (other than when I did Outward Bound when I was a teenager), and one I won't ever forget. 100% recommended, but be prepared. If you got hurt out here, or caught in bad weather, or god forbid had a nasty run in with a bear, getting out could be difficult. Definitely let someone know where you're going, and when you expect to be back. That said, don't talk yourself out of it if you want to give it a go. This place is special. Really special.
