Old shrubs - growth follows the knife?

[LexMitior]

I have moved into a house with an old garden. There are a lot of shrubs, lilac, forsythia, conifers and mahonia that have never been pruned. They are just growing at little at the top, very leggy, and not very attractive.

They are performing really badly and taking up a lot of space - is it worth pruning radically and see if they flower? The lilac and mahonia appear to be doing nothing but making small numbers of leaves... but they are in theory quite nice looking shrubs!

Broadly you want to prune just after flowering as very often they flower on the previous year's growth. So depending on where you are, that could be very soon. I pruned my forsythia today!
It's quite hard to prune an established shrub to death, so you may as well give it a go!

Obviously anything very dense should not be pruned now as it might have nesting birds within.

Conifers I have no idea! Don't they go brown when you cut them?

Yes prune away after flowering.

Mahonia you can cut back hard and it will re-grow on old wood. We had one we almost cut in half last year and it’s starting to bush out again nicely.

As others have said prune after flowering. The forsythia can be pruned hard soon, when it’s finished. It will grow new shoots that will flower next year. The same with the lilac and any fuchsias.

We had a dead lilac in out back garden. Three years after moving in we cut it to the ground (too difficult to remove the stump). It regrew with a vengeance a month or two later. I was seriously surprised but also impressed. We hadn't seen a bit of green on it in 3 years and had broken the top of the trunk by hand to confirm it was dead when we moved in.

Most conifers will not grow back after pruning. Yew is an exception, as is Cunninghamia, but it may not look any better.

Lilac may miss a couple of years flowering.

Thanks everyone - the forsythia is still flowering, the mahonia has finished, and the lilac hasn't put forth yet (doubtful that it will) and looks a bit dead except for a few tiny leaves.

The ratio of wood to leaf is about 9 to 1 - the old owner seems to have planted, watered and that was it! Likewise very old roses which are very woody and choisia also, again, not really been looked after but those can be cut and will come back.