I have used them, the only problem i really had was algae growing in and around the cups. I poked holes in the bottoms of them. Worked OK for me.

Sarah

I use clear pots indoors for seed starting and cuttings. I do it so I can see the roots before transplanting. Once I put them outside, they go into opaque containers. Everything I have read indicates that roots do not like light.

Like token28001 I use clear plastic because I like to see the roots. I usually, howbeit not always, sit the clear plastic in some other opaque container.

I have decided to use the clear cups because they are such a suitable size for wax begonias.I will set them in a cake pan to obscure the sides.
Iris

Root response to light varies widely by plant species from unfavorable to favorable. What part of the spectrum is included in the irradience (mostly a factor with artificial lighting) also has a bearing, so there is no way to offer a 'one-size-fits-all' answer.

Clear containers are prolly going to be inappropriate if they are ever to see the sun, because of heat build-up in media due to passive solar gain. Opaque containers absorb light at their surface, turn it to heat, and dissipate it into the air. Clear containers allow light to pass to the soil, where it is turned to heat and trapped there by the container walls. There can easily be >50* differences between soil temps in a white container vs a clear container in summer sun.

Al

Iris,

"I have decided to use the clear cups because they are such a suitable size for wax begonias. I will set them in a cake pan to obscure the sides."

That sounds like a good plan. Don't forget to put drainage holes in the cups. How you do that might be kind of a challenge. I once used a soldering iron to melt holes in plastic, but that was messy and smelly. I guess I would try an electric drill or Dremel tool first.

The clear pots could be an advantage, because it will let you see the roots as soon as they reach the sides of the pots and you can visually determine if your cutting plants are starting to get root-bound. Some plants, like Orchids, actually like clear pots. Aircone pots are clear and have a special design to get more aeration for the growing medium.

ZM

I just used a steak knife or scissors to poke 1-2 slits in the bottom of the translucent plastic party cups. You can stack a bunch at 1 time and plunge the knife down through the bottom of all at once (obviously be very careful) but it goes fast that way.