Typically you don't fertilize much of anything late in the summer/early fall since you want the plant to go dormant and not start producing any new growth. That being said some plants respond to lesser hours of daylight to trigger dormancy and others rely on a cold snap to make them go dormant. I haven't ever seen or heard anyone give information which camp clematis fall into.

If you do use something, why not apply something organic that will take time to break down over the winter like grass clippings or shredded leaves (some trees here are already dropping leaves because of the drought conditions we are experiencing), or even some sort of shredded mulch? These things will start decomposing in the fall, attract earthworms to the area which will supply their own organic additives (worm castings), and you won't have to worry about it causing excessive growth at a time when they should be going dormant. I personally wouldn't use anything other than that at this time of the year.

Miquel, do you shred your own leaves? I will certainly have alot here. Should I rent a shredder?

This (mulching gardens for winter) is something I've been thinking about as well. Not just for my clematis, but for all my gardens, since this is my first year, and this clay soil has not had any help for years it seems like!

I've expanded one garden that was filled with iris. Dug up most of those and divided and replanted a smaller number. I'm planting some perennials this fall, and next spring will put in a clematis. I was thinking about some store bought compost or manure. I have amended the bed somewhat with peat, as that is recommended here to improve the clay soil. What do you think?

Alice, I just run over them with the lawnmower and collect them in the mower bag. Makes a much easier way to shred and collect in one fell swoop. The added greens from the lawn, unless yours is brown like mine is right now, help the composting process.

I do have a small chipper/shreader but find it too cumbersome for leaves. The lawn mower with bagger is much easier.

Of course! That's perfect. Now I have a plan. Thanks Miguel.

No problem!

Aliceg8 - Instead of mowing my leaves, I suck them up with a leaf vac. It is electric (unlike the mower), so I don't have to worry about expensive gas for leaf pickup.

I also have an electric leaf blower that doubles as a leaf vacuum and have used it at times also. I prefer the mower since like I said you get both the browns of the leaves and the greens of the grass so you have a perfect mixture for natural composting.

so does that mean you wouldn't put down a little compost in the fall? i was planning to put a little down, maybe over some of the fall leaves, then a little extra mulch on top. we mulched everything pretty heavily last year, but i have some newly planted areas to mulch this fall and i was going to add a little more to the rest.

If you have compost, I would use it. Generally speaking, compost is not a fast acting fertilizer.

Compost and mulch to me are two different animals. Primarily compost is already decomposed material that is readily available for plant use. Mulch on the other hand may or may not be organic and breakdown over time but I tend to use mulches that are organic and that will break down over time and add tilth to the soil.