I'm looking for advice of an older clematis, Nelly Mosher. I feel like the plant looks a little tired. It is placed in a part sun part shade area getting about eight hours of sun a day. It has been a terrific performer and I'd like to make sure it keeps going strong. any advice appreciated

I don't do fertilizer but I could suggest you prune all of Nelly Moser down to one or two buds and effectively start again.

Every year I try to add a layer of compost at the base of all my clematis.

This one time... I dug a clematis (probably the Nelly Moser, the flowers looked similar), I dug up this huuuge rootball...
Like I could barely get it out of the hole... almost more than I could wrap my arms around...

It was growing in clay... where it had sent out adventitious vines at ground level, each time they'd been mulched, new plants rooted...

Anyway, the original rootball was replanted (in clay), and kept going...

I can't imagine a need to trim... I've been raising Cain with someone that keeps allowing their clematis to be cut back as an autumn tidying process...

Agree with Sue... I would add some compost before mulching.

Check out 'pruning groups' for clematis, Stone - they all have one, and Nelly Moser is Group 2/Group B. This group requires pruning late winter/early spring when it starts into growth, with each stem shortened to the first pair of strong buds. If this is ignored for too many years then I expect the stems may become weak and unable to support a good bloom season.
And stop raising Cain with the people that sort of know about pruning and remind them it should be done in the Spring

I do trim most of my clems back a bit after the first flush as they can get ratty looking and sparse, just creating growth in the upper sections if I don't, blooming near the tops, above eye level.
The majority of large flowered clematis belong in Group 2 and here's a site specifically mentioning Nelly Moser and tips for pruning and rejuvenating this Group 2 variety.
https://www.gardenia.net/plant...

Vals_Garden said:
stop raising Cain with the people that sort of know about pruning.

It's the turf guys suspected of cutting the vines back.

You can't really make a case that they know what they're doing.

As far as requiring cutting back?
Mine gets by without trimming...
I like having flowers at the top of the fence.

To continue....
I find that I agree with the sentiment that Gaia hates a tidy garden...

Seems like entirely too many people suggest cutting things back that do a lot better when left alone...

I'm reminded of the patch of foxgloves I had growing at a house that was purchased by new owners... I collected some seed and scattered in seed bed, trusting that I'd be able to collect more as the rest ripened...

The woman of the house went out and cut the foxglove to the ground & killed the entire patch... said that the internet told her to.

Anyway... the main reason why it's a problem about the clematis... the woman wants to share... with the plants getting chopped back every year, there's nothing left to propagate!