Can anyone help me with cutting back these plants?

[Dachshelp]

All my plants are in pots as no beds. I have a few lavender and I have read conflicting advice, cut it back in mid spring but also cut it back in September?! When do I do this? I know if you don’t it comes all reedy and I would love a nice healthy, plump plant this summer!I also have climbers in a big pot against trellis, what about those? They grew loads this year so there is a lot of dead twines all over the trellis?

The others are ok and don’t need it but I want to really encourage the plants this year to increase the bees and butterflies etc but worry I have left it too late?

I’m sure if you give your lavender a hair cut now it will be fine, I used to leave mine until the spring, I shaped my new one in November and it’s looking great. They are pretty robust.

What climbers do you have, clematis vary depending on the variety. www.rhs.org.uk/advice/profile?pid=109

The basic rule of pruning lavender is not to trim into brown, dead wood. You'll usually find brown branches at the base of the plant. Remove them only when they are truly dead. Never cut them back, hoping to stimulate new growth.

I've cut that from gardeningknowhow.com
The only problem might be judging what is dead wood and what is dormant wood at this time of year. Safest bet is to be not too ruthless. I wonder if that is why they say prune in mid Spring as you might be able to see the new shoots by then, and you can be sure you're not cutting them off but instead trimming and leaving some to grow.

I have attached photo of lavenders, I don’t know what is dead though? When I haven’t cut them (some others) it just went long and lanky and not many flowers so I really want to try to help these ones to see if I can get them thicker and more flowers.

The climbers are clematis?

The easy way to tell which part of the lavender is able to produce new shoots is to prune when you can see tiny green new shoots appearing. So if you wait a bit longer, you'll be able to see that. But looking at the pot in the foreground, you can see that the shoots are partly covered with long leaves, but have an area nearer the base which don't have the long leaves. For safety at this time of year I would prune leaving about an inch of the long-leaved bit, and would definitely not cut back to the scrubby basal bit. If you left it till spring, you'd see the new green shoots coming and would be able to cut back a bit further.

I have lavenders on my gravel terrace which I don't really want there, and I cut them back to base each year - they spring back better than ever. My former NDN had a lavender hedge which he'd cut back quite robustly, and every few years he'd overdo it and lose the lot. So as with so much of gardening, it's not so much about the rules, it's about getting to know your own plants and your own garden.

Clematis - depending on variety they fall into three pruning groups. But as a rule of thumb, prune after flowering.

Early flowering ones flower on last year's growth, so you need to prune early to give time for them to grow ready for next years flowers.

Mid season ones, again prune after flowering, but not quite so vigorously. These are mainly the big-flowered ones.

Late season ones flower on this year's growth. So again, prune after flowering, but because they're not going to grow over winter, it's better to prune, not immediately after flowering, but early spring when they're ready to start growing again.

Pruning isn't done for the plant's benefit, it's for your benefit, to keep the flowers where you can see them, instead of in the tree tops.

@MereDintofPandiculation so if I cut basically the tops off the lavender for now? Will it benefit from that?

With regards to the clematis, I think is alpine Constance?

Will it benefit from that? Not necessarily, but you will benefit, because it'll look tidier.

I'd probably leave it till I could see tiny green leaves sprouting, then do one good prune, rather than tidy up now and do more pruning later when it's more obvious how far down you can go.

With regards to the clematis, I think is alpine Constance?

Clematis alpina "Constance" Pruning group1. Pruning not necessary but if you want to prune it should be done late spring, after flowering. See this link for more.
www.rhs.org.uk/advice/profile?pid=344