Bob wrote:
Hello,

Have the typical outside Deck constructed of (some type of) pressure
treated wood.

Have several flower pots, and good size planters on it.
When it rains, or course, water seeps between the bottom of the
planters which are absolutely flat and the wood. I guess mainly by
capillary action.
This can't be good for the wood, as the water, with no way of
evaporating stays there, and the wood therefore stays wet for a Very
long time.

Is this something to worry about or be concerned with ?

if a problem, what would you recommend for weather-proof small feet to
glue or fasten to bottoms of the planters and pots ?

It will likely result in early deck rot. You can buy rubber feet with adhesive
for attachment. Or, you can get the pots off the deck. Just watering the plants
is going to have problems, long term. It will always be moist under them if the
pots are porous or have drain holes.

I once built a shelf outside a deck I built, for the pots, using pressure
treated wood with big gaps for all wood that had contact with the pots.