Do your soil test first. There almost no situations, other than extremely low pH, that could keep you from planting the imperial clover this spring. Another reason would be location. You wouldn't want to spring plant a perennial in the deep south.

If you do have a pH that's lower than 5.0, you may consider adding the lime and disking it in throughly now and planting in the fall. This will give the lime a few months to begin correcting the pH.

I had this occur on one field, when I soil tested again rechecked the pH, I had to add a little more lime. Now, I always add about 30-50% more lime than the test calls for. It seems to de-acidify quicker and last longer before it turns acidic again.

Good luck. By the way, I agree it's tough to beat the Imperial Clover. I've had good luck with the Imperial Extreme in my drier fields.