Hi Grace My answer may not help you at all but... I live in Sf and have grown dahlias out in the sunset for years (which is one of the worst environments for growing flowers) and in my opinion, you are causing more work than you need to for yourself. I NEVER have started my dahlias indoors, I never have dug them up for overwintering and I rarely even touch them after they bloom in year one. And I (just being honest) have a yard that is the envy of my friends and neighbors. Even in heavier rain years, I never worry about my tubers and in years like this, I find I have to go out and water in the winter in order for them to get ANY moisture. Do I lose dahlias? Sure do. But not often and usually only when I am lazy and allow the snails to have at em when they start sprouting. But if I lose a few (out of 90+ and counting), it gives me an excuse to buy more tubers the next year! You may well grow beautiful dahlias with all the dedication you are showing but for my money, it is much ado about nothing. Dahlias are hardy and once they get used to their environments, they last forever. And you know well in the sunset we get up to 2-3 months of NO SUN and heavy fog. So if I can grow beauties with little maintenance, I am sure you can also. If you prefer the high maintenance route, go for it. But I think you will find it a full time job because there will ALWAYS be something - mold, rot, lack of water, too much water, snails, too much heat (sun), not enough heat, freezing temps, long foggy months, staking, and maybe , just maybe, the tuber was no good from the get go DESPITE what you do! Good luck. And if you live in the sunset and want to see my yard some time, I have dahlias from May to November but the best month is August. Come on by!

Your dahlia needs an intervention! A taller stake and ample tying would help corral falling branches but your problem sounds like it would be solved easily by disbudding. Leaving only one bud to mature instead of 3 heavy ones will make for much less stress on a branch, more room for a solitary flower to develop to full beauty and less likelihood of loosing that main bloom. On each growth tip, fold back the end leaves where buds have formed. See the main bud and slide your thumb or fingernails alongside it to carefully snap off the little side buds trying to form. Best done in early a.m. or evening when they aren't rubbery. Check growth tips the day after watering or a rainfall as those little buds develop fast. That should help, I think. Below: leave the center main bud alone, scrape or break off the side buds so it looks similar to the blurry second photo. Sometimes, depending on variety, the side buds are staggered up and down the stem a bit, but should still get removed for best flower development and weight reduction on the stem. Here is a link that might be useful: Disbudding

Love opposing views. I have been storing dahlia tubers in plastic bags for over 20 years now and I do not seal the bag so there is some air getting in there and my success rate is outstanding. I store several thousand tubers each year. Not only do cardboard boxes wick moisture but they also can rot when they they get moist and can cause rotten tubers. And I have heard of very many people having their entire crop of tubers eaten by mice that chewed through the cardboard boxes. I experimented with the potting soil and put my best tubers in it. They stored much worse than those in vermiculite and sprouted in storage weeks before the others. Sprouting while in storage is not good. Potting soil is not a good storage medium. I would use nothing at all in preference to potting soil. Swan island Dahlias uses no storage medium and places their tubers into plastic tulip crates that are lined on the top and bottom with sheets of newspaper. There success rate is pretty good and they store several hundred thousand tubers each year. However, they have a dedicated potato root cellar for their storage facility and the temps an humidity are ideal. Off gassing does not occur in plastic bags at any rate that hurts tubers if you use vermiculite in the bag and/or you dry the tubers before storage.

Could be many things...three that come to mind are: -underground critter ate the tubers -those four plants had excellent drainage versus the rest of your plants, and are suffering from lack of water -spider mite infestation Glad the rest of your dahlias are cooperating with you this year! You've had a tough run the last couple seasons- may this be the best yet!