Question 861272
DISCLAIMER: I am not an artist. I am just a math geek, so I can give you some calculations, but 
 
You are right about the work involved in using 1" tiles.
With a diameter of 34.7", the perimeter of one planter (in inches) would be
(34.7)(3.14) = about 109
Then, the surface area for just one planter (in square inches) would be
(24)(109) = 2616, and for all 7 planters it would be over 18,000 square inches.
However, a 2" tile has a surface area of 4 square inches,
and wit 2" tiles the number of tiles would be about 18,000/4 = 4,500.
Better yet, with 3" tiles (each one covering 9 square inches),
you would use about 18,000/9 = 2,000 tiles.
With 4" tiles, you would use about 1,100,
and with 6" tiles, you would need about 500.
 
On the other hand, avoiding sharp angles and gaps between planter and tile could limit the size of tile you can use. Besides, with 500 tiles (about 70 tiles per planter) your mosaic design may not be too interesting.
Calculations are fine, but I would try just one circle of tile (maybe temporarily/loosely attached) around the perimeter of a planter (or a cylinder with the dimensions of the planter), to see how it fits and looks.
 
Dividing the circumference of the planter by the tile size, gives a good estimate of how many tiles fit in one circle around the planter.
From a circumference of 109 inches, I found:
6" tiles --> 18.17 tiles (so 18 would fit)
5" tiles --> 21.8 tiles (refined calculations suggest that 22 may fit incredibly tight)
4" tiles --> 27.25 tiles
3" tiles --> 36.33 tiles
2" tiles --> 54.5 tiles.
 
The number of tiles determines the angle between the tiles.
With 6" tiles, you get 18 tiles per row around the circumference of the planter, and the cross section of the tiled planter would be an 18-sided polygon.
As you go around an 18-sided polygon, at each corner you change direction by an angle of 
{{{360^o/18=20^o}}}
Edge on, the side of the planter would look like this:
{{{drawing(1200,400,-7.5,7.5,-3.75,1.25,
circle(0,-17.41,17.41),
rectangle(-3,0,3,0.125),
triangle(0,-17.41,-3.07,0,3.07,0),
triangle(0,-17.41,-3.07,0,-8.84,-2.10),
triangle(0,-17.41,3.07,0,8.84,-2.10),
line(3.14,-0.02,3.17,0.09),
line(3.17,0.09,8.95,-2.01),
line(-3.14,-0.02,-3.17,0.09),
line(-3.17,0.09,-8.95,-2.01),
green(arrow(-3,0.125,-9,0.125)),
green(arc(-3.07,0.125,4,4,160,180)),
locate(-5,0,green(20^o)),
arrow(5,-0.2,3.07,-0.2),locate(5.05,-0.1,0.27inch)
)}}}
The drawing (to scale) represents a 17.41" radius circle (37.4" diameter planter, covered by a 0.06" layer of glue), with 1/8" thick 6" tiles glued around it.
The tiles will be glued at their centers, but the edges will be about 0.27" or 1/4" from the curved surface of the planter. Would that gap be a problem?
The angle between tiles would be {{{20^o}}}. Is that a problem?
Each planter would have 24/6 = 4 rows of 18 tiles, for a total of 72 tiles. Is that too few tiles for your design?
If any of those issues is a problem, smaller tiles would lessen the problem.