Alina W

red maple

It sounds like you have dieback. The white branches will be dead - cut them out, and clean your secateurs before cutting into live wood. The rest of the tree should be OK - give it a feed to encourage it to branch more.

What to do with lemon plants

Lemons need to be kept frost-free in winter.

Considering where you are, if you built them a shelter and wrapped them well with fleece, including the pots, then I think there is a reasonable chance that they will survive.

The other thing that you may not know is that you can prune lemons to make them small enough to bring indoors if you want to - I wouldn't do it too hard, but they do re-grow well.

Good luck!

Is it too late to prune a grape vine?

I would say it's too late - you may make it bleed to death now.

Beech hedging, white powdery stuff?

Take a magnifying glass to it and check if it's beech aphid. It looks like fluff close up, but there is an insect beneath, and a serious infestation can kill the plant.

Narcissus not flowering

They're too shallow, then. The bulb needs twice its own height of soil above it. So, if your bulb is about 7cm tall, it needs 14cm of soil above it - about 15cm is usually the maximum needed. This is especially important if you have dry, sandy soil, which you probably do.

Once the bulbs have finished flowering, dig them up and plant them deeper, then feed and water them as usual.

Hopefully, you'll get more flowers next year.

Floppy Cornflower seedlings

If they are indoors then they are too warm and not getting enough light.

Try putting them outside on warm days in a shady position, but make sure that you bring them in well before nightfall. If they have to stay indoors, move them to the coolest room that you have and try putting white card behind them to reflect the light onto them.

Geraniums

Have they been outside? It could just be birds.

Or have you watered them when it was sunny? Any water droplets on the leaves could cause marking.

Viburnums, periwinkles, butchers broom, berberis in full shade

Periwinkles do very well, even the variegated variety. I've seen them thrive in really poor subsoil and rubble with no sun to speak of. Good luck!

non flowering bullbs

Your bulbs may well have split themselves into bulblets if they're hyacinths. These can do with spacing out and, as already said, a good feed to help them along.

I'm a great believer in feeding bulbs - my garden is crowded, and the soil can't support all of the things there without some serious help.

Fuchcias - to cut back or not to cut back?

Yes, you can take them back to produce a bushier plant. If you don't want to knock them back too much, cut back to roughly 4"/10cm and leave a few of the new shoots in place.