I use a Staedler lumocolour fine point. It lasts a lot better than the pencil you get with the labels.

And I use a Dymo tape machine bought from Aldi.

Yes Scotkat I use a Dymo as well but find the labels don't always stick very well. Do you use plastic or paper tape?

We've been having success against a different problem, and we've found that black plastic labels with white paint pen have lasted well, so far over 2 years without noticeable fading.
We got the labels from The Essentials Company, but have since got replacement pens locally.
Our problem, incidentally, had been a long-standing problem with blackbirds pulling out any white labels, no matter how deeply inserted in the ground, and littering them all over the garden.

Pencil ?

I use a Sharpie but don't often bother with labels as I prefer to keep photos and plans - used to be on paper but now electronically.
I write on the rim of my potted hostas.

Pencil

I like the Edding 8400 CD pen, but an HB pencil is just as suitable.

Thank you very much folks I'll have a try and see what works best . Think I'll try hb pencil and cd pen and see which lasts longest . Thanks again

I use a Laundry Pen.