Lack of sun and damp conditions work well for encouraging mildew on plastic pots, too.

I clean my terra cotta and plastic pots using a mix of dish soap and water.

I have two large planters that are some type of thick double plastic that looks like gray concrete. You can't tell the difference by looking. I give them a quick clean every spring and the dirt that lingers give them a natural looking concrete patina. I really like these planters and they were around $20 several years ago at Walmart.

I have some that I have had for about 10 years and they are just now starting to look a little worn at the rims, but other than that, they are great. I use packing peanuts tied in hosiery for drainage which keeps them light and easy to move (I have very large ones). Mine were more expensive than Tuesday's, but well worth the price since they have lasted so long. I think I paid about $80 each for them.

My recently purchased planters for my back door, solid concrete, heavy and needed in FL. for storms & strong winds,bought these at Lowes for $20.00 ea. saw the same in resin at Target for $50.00ea. are you kidding me?? I painted to blend with my house no plain ole grey concrete for me!

Cyn, the peanuts in hose is a brilliant idea. I have two enormous not-clay planters that I like to be able to move. Right now I have cinder blocks on their ends inside and a plastic pot on top. heavy, but it can be disassembled. Your way would be so much better.

My faux planters are in a shady area and they do get a bit green, not terrible. I call it patina!

I prefer foam over clay because it is lighter and doesn't crack it cold weather. I leave the soil in them.

I have used solid blocks of packing foam, coke cans and 2 liter bottles as light weight fillers in large pots that I have. Sure helps on cost and in ease of moving to the garage in the winter.

My only problem with the composite planters is that they sometimes chip. I had a eureka moment the other day when I saw the paint for plastic items. I may be able to save 4 with some spray paint.

SusieQ, I just bought those same concrete urns at Lowes! Incredible price, but they were so heavy and hard to move they are staying in their current position FOREVER! I love how you painted yours.
I can always tell a fake planter from the real thing. I'll buy clay or concrete planters no matter how inconvenient.

I have a few decorative clay pots, but don't use them anymore. Much prefer the clay look with a lighter weight. Don't care for concrete pots at all.

I buy big concrete ones, and I found the perfect spray paint color for them...it is a very matte, dark brown. It is actually camo spray paint! It looks so perfect!

The packing peanuts are an excellent lightweight filler for extra large pots. Just be sure to make sure the peanuts you use are not made of starch as they will melt when watered! (Biodegradable packing peanuts)

I love mildewy pots and once they start to get white and "old looking", all the better to me.

However, I have a lot of containers and find the lightweight, foam types to be very nice although over time, they can get as beat up looking as a terra cotta pot.
I would look for the ones that are stained- the color is intrinsic to the pot- and particularly avoid the ones that look painted. They will flake.