Unhappy Forsythia

Folks, I'm hoping you can help me. My forsythia is looking very sad. The leaves are blotchy yellow and also have some brown marks too. There's no sign of pests. I have a hunch what it may be but I am hoping someone can give me a better idea. Nothing has changed in its care this year.

Hoping my images attach okay, I could only find an option to attach them as a URL

 

Hi, have you fed and watered it well since flowering?

I'm finding some of my shrubs look like that and are already dropping yellowing leaves. I feel sure it's to do with the heatwaves this summer - in this area anyway.

You may of course had the opposite problem of too much rain!

 

There are several things it could be, is the soil particularly waterlogged in that area ?

It's certainly a fair size, does it usually flower well ?

 

I've been here 3 springs and it has never really flowered. The first two years I assumed it was because they pruned late summer for sale and then I autumn pruned the following year not knowing any better. I expectednit flowering this spring but it didn't.

It's clay soil but on a slope so it doesn't really pool and stay overly wet in that area. I don't actively fertilise it but it gets a good compost mulch every year. It's not draught/heat as we've had a mediocre summer here in South East Scotland

 

I was a little concerned it could be mosaic virus because of the blotching but I've only ever seen it on a houseplant before so wouldn't know what to look for on outdoor plants or even if they can get it

 

If you pruned in the Autumn, that would explain the lack of flowers.
The best thing is to prune just after flowering.

Personally, l would leave it for now, even though it looks rather sick.
The leaves will fall around late Autumn and this should help to see the state of the soil at the base.
I would then prune in late Spring after it's produced any flowers. In view of its size, you could prune it quite drastically, or take out a third of the stems next year, a different third the year after, and the final third the year after that.

I would be inclined to really cut it hard back in late Spring next year which would possibly mean you wouldn't get many flowers in Spring 2026, but it would rejuvenate the shrub as a whole, and in the following year it should flower in all its glory.

Others may have a different take on it though .

 

They're best pruned after flowering, whether it's an all over haircut, or a more balanced, natural approach. They don't like being too dry, and they always flower very readily on this side of Scotland, so it's pretty difficult to overwater them unless they're sitting in a bog. They're one of the easiest shrubs to grow here because they need no attention if the soil's half decent. Your conditions should be fine for it.
I think it just needs some hard pruning to rejuvenate it. Nothing to lose because it's doing nothing for you as it is
You can try the renovation pruning of taking a third of the stems out completely, as described or you can just take it all back quite hard in late spring to let the renovation happen more quickly. However, you could cut it back a good bit now [about a third to half] which will allow some new growth before winter, and you may even get a few flowers next spring/early summer, and can then follow the late spring/early summer pruning to keep it healthy.