Alfalfa takes a while to break down. I don't see any trouble with adding it now. In fact, that I what I'm doing this afternoon.

Alfalfa is candy to all sorts of rodents, if that would be a consideration over the winter. I would want to apply it at a time when it would rot promptly.

There are two things you get from it, the nitrogen fertilizer value which is released across two years and more, once it is rotting or in contact with the soil; and the growth stimulant triacontanol, which is slightly soluble and leaches out when it is watered heavily. I am not sure how long it takes to extract most of that, but some apparently gets to the plant within, say, three weeks.

It seems like spring to midsummer would be the best time to use it.

Alfalfa has an N-P-K of about 3-1-2 or 4-1-2 and, as said, also contains the growth hormone, tricontanol. It is broken down and its nutrients are released primarily by bacterial action. And bacteria are pretty well dormant at any temperature below 40 degrees F and don't become really active until it rises above 50 degrees. That is about all you need to know to figure out what happens to the alfalfa you put out -- and when.

Here, I put alfalfa meal and other organic materials out and cover them with compost as a mulch in December (usually) and agian in August. And I've never had any problem with rodents or other pests from doing so.

Thanks for all the answers! I think I'll be a brave soul and put the alfalfa down when I mulch this winter. The roses are away from the house so hopefully if any rodents come calling they'll stay away also.
Sharon

The problem isn't attracting rodents to your home, it's that rodents will eat roses during the winter. That's why most cold areas that cover their roses for winter protection do so after a couple of hard freezes. The mice have already set up their winter abodes by then and aren't tempted to nest next to your roses and use them as their pantry all winter long.

And then there's RABBITS. Alfalfa is the main ingredient in rabbit food, so if you have a problem with them already, you might want to think twice about putting out something that draws them to your roses when all else has died off for winter.

I was going to do the same thing and then had second thoughts...safer when there's lots of fresh clover in the spring.