When the soil is frozen ;-)) Really, any time up until December is fine as long as you can easily work the soil. Spring flowering bulbs need about 12 weeks in the ground to develop the proper root system to provide good growth and the beginning of December is usually a good cut-off point for that happen and still have a good, on time bloom season.

You can plant later if your soil is still workable - I've planted in January - but it may delay the flowering season.

I usually plant a batch of bulbs when I visit my parents for Thanksgiving. Some come up, but not as many as I put in. (That could be because I usually buy bulbs on clearance, I'm planting them in a windy rain-shadow, or because of squirrels). This year I purchased some nicer bulbs, and don't want to ruin them.

I find our soil usually freezes in late December or January.

Don't really care about delayed blooming...care more about survival rates.

I'm in Zone 6, by the way.

This post was edited by edlincoln on Thu, Nov 6, 14 at 21:11

Due to a brain freeze I found a mesh bag in my cool basement,with at least 200 bulbs of an unknown plant that were sprouting in October. Having no idea what they are the fact they were growing left me no choice but to plant them. I am pleased to report that what ever they are, they are growing like gangbusters. Old age can be a lot of fun. Al