I've always planted parsnips in the spring and harvested them in the fall after a good hard freeze. Sweet as candy.

I'm going to try some parsnips in the fall. I've never grown them before.

My cooperative extension publication says to harvest in the spring but before the second year's growth begins.

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.

Obviously my climate is very different but I'm not too sanguine about sowing parsnips in the Autumn. In our temperate climate we sow in early spring and harvest through the following winter and next spring. Parsnips need a long growing season. If you sow in fall I don't see how you could harvest the next spring. They might germinate but they would not grow all through the winter, especially in Z3.

In Colorado I always left mine in the ground through the winter months and at first thaw dug them before they stated to sprout.

The object of the exercise is to give the parsnips an early start in the spring. The ground is frozen during the winter and the parsnips aren't growing. By the time the ground is workable and the parsnips are planted and germinate (I get slow and poor germination), the parsnips don't have time to bulk up. Is flowering a function of size or over-wintering?

ljp, your season is too short for parsnips. They need 110 frost-free days. Your only choice is to pre-germinate them indoors and place them outside under cover, which is quite a bit of work.

But I think you should grow beets, turnips and rutabagas, which make it in 60, 60 and 90 days instead. In fact, rutabaga is probably your upper limit. Parsnips flower after spending a winter outdoors, just like every other biennial.

My seed packet was mismarked and parsnips came up on their own this spring. They are down there but plants are going to seed now (mid-June). Should I still let them go til fall?