For regular turnips it may be a little late, but Hakurei turnips would work very well. All those crops you listed are frost-tolerant, so you have way more than 60 days. The spinach and kale are particularly tolerant and will be fine right until the first permanent snowfall. OTOH, you have to add a 25-50% extension to the DTM to account for fall's shorter and ever-shortening days. I would also suggest radishes, tatsoi, bok choy, gai lan and claytonia. IME, freeze damage thresholds are about like this (this is without row covers): Least tolerant: lettuce and bok choy - mid to high 20s F Tolerant: beets, turnips, radishes - mid 20s F. Mound up soil around the growing root to prevent the root from freezing. Very tolerant: kale, spinach, tatsoi, claytonia - mid teens F This post was edited by Slimy_Okra on Fri, Aug 15, 14 at 21:48

We do a great deal of succession planting in Zone 5. We will plant last sunflowers (Sunrich series) around July 15. We just did our last planting of zinnias yesterday. I'd get the bachelor buttons in soon. ; )

Buzzy, I'm guessing that you're question hasn't been addressed because any of us would have to do the same legwork that you need to...check out some of the reputable seed houses and see what's on their lists. I'd expect that you could find seeds for those plants 'fairly' readily...maybe not at one mail order location, but probably between a couple. It's very common for me to buy seed from a couple of different locations. Maybe you could narrow your search a bit, and just look through 'fragrant flower seed'. I'll attach the google list for you; some of the plants look absolutely delicious! Here is a link that might be useful: click here

Image by: wintersown Daffodils forming seed pods Deadheading a plant (removing the wilted and faded flowers) will also prevent the formation of seeds from those flowers. Why is that? When a plant is pollinated seeds will form at the base of the flower pod...above the stem, but below the blossom. If you pinch off the faded flower then the area where seeds will form is also removed. I'd like to keep my plants looking tidy. Can I do some deadheading and then collect seeds later on from the new flowers when the plant reblooms? Yes! This works fine. Most annuals, perennials, and biennials will put up another flush of blooms if the plant is deadheaded after the first time it blooms. By removing the flowers the plant is "frustrated" in its attempts to set seeds and so it will try again....that's why deadheading will usually produce a second set of blooms. Let the second set of blooms go to seed and collect seeds from them. Are there some plants that might not rebloom? Yes...there are. Most spring blooming bushes will only set one flush of blooms regardless of their being deadheaded. With my azaleas, hydrangeas, and forsythias I do not deadhead them if I want to save their seeds...there are many other bushes that are like this, not just these common garden favorites. Also, I never get a second set of blooms from plants with tuberous roots, or those grown from bulbs. My daylilies don't rebloom, my iris don't rebloom, and my tulips and daffodils don't rebloom. There are some modern hybrids of iris and daylilies that are called "reblooming" varieties and so you can try deadheading those hybrids and hopefully they'll rebloom and still set seeds for you. I personally do not have experience with them so I cannot say yay or nay about any expectation of a second flush of blooms that will set seeds. How do I learn if my plants will set a second set of blooms? Deadhead less than half of the spent blossoms. Seeds will set on the remaining faded flowers. Observe the stems where you removed the faded blooms and look for signs of new bud growth. Hopefully, in your garden zone, there will be sufficient warm days to produce more blossoms and you'll be able to collect another set of seeds from the same plant. Experience is a good teacher....you'll enjoy learning about your plants and will be fascinated by the reblooming process. Trudi