I tend to use a soft pencil as well - it can get rubbed off but Hosta's tip helps with that problem. Good fade resistance and a pencil doesn't dry out if you leave it on the potting bench in the sun....
If you particularly want to use a pen try a black "Sharpie - ultra fine" (larger size nibs are available). These are the pens used by many of my local nurseries - and they are the most fade resistant I've used. The ultra-fine nib allows you to write neatly and put additional info on the label if you want to. However, the ink will still fade after a year or two.
If you want labels for plants in the ground you might want to look at black labels which you write on with a white pen. I have lots of white labels in the ground and at this time of year it looks a bit like a graveyard...🙄
Heaven is ... sitting in the garden with a G&T and a cat while watching the sun go down
Sharpies don't work for me at all and wash off in a month or so (outside). Following recommendations I now use a Stabilio Write-4-All pen. I put out a load of test labels and after a wet winter, the writing is clear and present.
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If you particularly want to use a pen try a black "Sharpie - ultra fine" (larger size nibs are available). These are the pens used by many of my local nurseries - and they are the most fade resistant I've used. The ultra-fine nib allows you to write neatly and put additional info on the label if you want to. However, the ink will still fade after a year or two.
If you want labels for plants in the ground you might want to look at black labels which you write on with a white pen. I have lots of white labels in the ground and at this time of year it looks a bit like a graveyard...🙄