We've all tried endless ways to label our plants, only to find that infernal sliver of white plastic completely blank a year later. I've found only three ways to write on labels that actually last longer than my memory.
1. Grease pencil/China marker, which smart nurseries use on the pots themselves. It's something like a crayon, comes in white (for black pots), black, and colors. You'll be able to read the plant name years after the plant has gone to garden heaven.
2. Pencil. Not easy to read in bright sunlight, but the writing is still there a year later.
3. Aluminum tags that you write on using a pointy thing like a pen. Ink doesn't matter. The impression will remain as long as the label is intact. Expensive for gardens with lots of plants, but this is how botanical gardens label their plants. You can buy them on thin wire to wrap around a branch - cheaper than the stand-up version.
3.5 Craft pens that contain actual paint also work (paint doesn't fade). This is too complicated for me, but it does work.
WHAT DOESN'T WORK: Any pen that claims to be permanent. Sharpies are great but they fade in the sun, leaving not a trace of information. Ball point pens won't write on wet surfaces. The list goes on.
An exotic plant grower I know makes two plastic labels for each plant and slides one down between the pot and the soil so it's completely buried. Years later, when the one above ground has been snapped off, stolen by the dog, removed by a customer, etc., he can still dig down and find the original. If you're a collector, this makes a lot of sense.
One last thought: I visited an old garden once owned by collectors of rare plants. The water had been turn off for years, leaving 5 acres of vacant pots, only an occasional survivor. The tags prevailed, however, and most had been written on ... plastic picnic knives. Not glamorous (Martha Stewart would be horrified) but cheap, and clearly they are not biodegradable.
