Here in NWKS, it is suggested that planting by about 7-15 is necessary. My problem was finding seed potatoes at that time. Last year, I bought extra in the spring and tried to save them, stored in dry sand to use for the second planting in mid July. This was suggested here a few years ago by a Mr. Paquibot? (spelling guess. Sorry sir if you are still around.) Have not heard from him in several years, but I appreciated his input about potatoes. It did not work too well, only about half went dormant and were usable in July. Then we had an early winter, and production was not good. I have given up growing potatoes, having decided it is too much work growing them to save, without having a root cellar to store them for winter use.

In most places they are harvested in late fall/winter. You may have very cold winters judging by your zone, which means the ground is frozen early and stays frozen into early spring. As long as the ground is not frozen parsnips can be harvested. You would have to plant early enough for them to size up before the ground becomes a frozen tundra. In most parsnip growing areas (Europe, northern North America) , planting as soon as the ground can be worked. They are biennials so they seed the second year. Those left over winter will seed with the coming of long days. If you are in zone 3, I don't think fall planting (October, November, December) would be a great idea.

Start your plants for fall indoors. Dave

I posted this on another thread, but for what it's worth: "The 4 Canela Russet potatoes I planted on July 28, from seed potato came up on August 5, Monday, and the plants are now 6" tall. The biggest is 12" diameter." I might experiment with one of those plants, leave it in the ground, see how many of the spuds will germinate after spending the winter in the ground? You're not too far from me, the time to germinate may still be similar. Good luck.