The big markers are strips cut from scraps of vinyl siding. It's much
heavier than the vinyl blinds and holds up much longer without getting
brittle.

Each pot also has two small pieces of vinyl blind that are buried to
protect from fading but mostly to make sure at least <one> label won't
get lost.

I use Painters acrylic paint pens for markers. Betty posted a link for
an online source - thanks again Betty - saves a trip to Wally world
where they are out of stock half the time. I ordered from them and also
am trying one of their other brands of acrylic paint pen in Bubblegum
pink. I color code seed germination pots for each year's crosses so I
can quickly figure out which ones to bring indoors in Jan from the prior
two years for 2nd & 3rd yr germination and which ones to discard without
having to dig out the tags and read the date on each. Last year, the
day-glo pink acrylic paint in a jar from the hardware store was not
sunfast, so they became white labels.

Year before last, I tried a comparison of regular Sharpie pen vs their
new "industrial strength" Sharpie. So far, the industrial has held up
much better, but I still wouldn't trust it for more than short term
labeling or buried labels.

Linda Mann
east TN USA
zone 7