Hi Calliope, I know what you mean, but those plants that can be planted before frost date usually can take frost easily. My nasturtiums, e.g. went through a few snow falls last year with their beautiful leaves and flowers before they finally yielded. I agree that one must know his area well and know how to estimate (though we cannot be 100% accurate). For some annuals, I wait 2 weeks after our formal frost dates, then check the forecast for the next 10 days, and if it looks good I can plant them. For tender annuals, I might wait a little longer or start indoor. For half-hardy or hardy annuals, I can start earlier.

Germination isn't the problem with the spring things. Even things that grow in cold usually will germinate well at higher temps. The issue is that they will bolt in warm weather. They grow best when it's cooler. If you have a shady spot and if you can keep night temps relatively low, you might be fine. I'm in zone 5, but I'm on a roof deck and it's hot as blazes; if I planted these things at this time of year, I would be wasting my time. You might be able to go to a store and find some lettuce starts. You probably have 6 weeks before it gets really hot and the lettuce would bolt. If you got in partially grown plants, you could use the "cut and come" method" with leaf lettuce or even romaine - just cut off some outer leaves, leaving some core to the lettuce. Those inner leaves will continue to grow and in a few days or so you can cut a few more. Next year consider getting these things in a bit earlier, such as late March or early April.

For best results I start sweet peas in October. At this time I would pick up seedlings in six packs so they bloom before it gets hot. Al

The question really is whether you think you'll get a hard frost (e.g. the moisture in the soil actually freezes to any extent) or not. The tubers will survive in the soil with cool temperatures, just not frost. Remember, they are shallow root plants so you only need to freeze a couple of inches of soil and you'll kill or damage the roots. It would take several weeks of ground frost to kill the tuber (think about what happens at the end of the season.) I too am in Zone 5, and am on the side of a lake (which usually means our temperatures are slightly higher than others) but you are more daring than I. But my reason is that most of mine are 8" tall already and I don't want to have to bother with coverings for frost warnings. Most of my tubers took 15 days to go from nothing to a cuttable sprout. Were they in the ground, that sprout would have had a couple of sets of leaves above the ground and would have been highly susceptible to frost. The up-side of your plan, however, is that even if the above-ground part gets frosted, a root system should get established as well, so a new sprout should come up quickly. Good luck, and let us know how it works out for you. Cheers, Russ