No, it's a chemically inert substance. You can also poke holes in the sides, although
I prefer holes in the bottom. An expert grower, the president of my AV club, uses styrofoam for starter plants. She puts them inside little plastic cups that fit perfectly. I don't know where she gets the outer plastic cups. They are sturdy, with wide bottoms. So they don't tip over like the solo cups tend to do. You can't beat the price. They are biodegradable.

Years ago there were commercially made styrofoam pots in 3," 4," 5," & 6" sizes. They looked just like clay & plastic pots and many were squatty just for AV's. The main advantage was that they breathed like clay; however, they were tipsy and it was easy to knock them off a shelf. But I liked them & kept using & reusing them for many years. I think my last ones bit the dust some three years ago.
I do use styrofoam cups on occasion & they work just fine. I have the 6 oz size which I often cut down to make a shorter pot. I don't have to purchase any smaller plastic pots because I use styrofoam, solo cups, and yogurt containers.

Terri

I did a lot of perennial first transplanting into dixie cups (clear plastic) and really enjoyed being able to see the root structure expanding in the cups (just an idea).

Hmmmm, now I wonder if I could start baby plants in a styrofoam egg carton with the lid cut off.

Yes, I also asked that question and someone on the Forum replied they have done that very successfully. Just slice some slits in the bottom for drainage. You can also use the cardboard containers, however, they will need to be watered more often. I did not try it myself, I got some containers at the garden shop that are deeper than egg cartons, about 1 1/2", that work well. Joanne

interesting... i may have to re try Styrofoam again .... i tried it several years ago but the Styrofoam plant did not do as well as the other plant ... it was an experiment ... but i should do it again .... there were so many variables, it was a bad experiment.

i'm using the plastic cups full of perlite for my av's but they're not recyclable. This would be a much better idea environmentally ... ? I think.

It is probably not the best substance. Probably some experience is needed before using styrofoam as every pot material seems to behave differently. People I know stopped using styrofoam several years ago. Me, too, as the results I got were not as good as with normal hard plastic pots. So I was surprised to receive starter plants in styrofoam. I use solo cups or hard plastic pots. I was just reporting what others have tried that has worked to start leaves. After a while, they have to be put into regular pots designed for the purpose. Joanne

I think all plastic is recyclable these days. Joanne

I am not sure why it would make a difference if they were in styrofoam as long as the styrofoam doesn't emit anything harmful. I grow minis and the small styrofoam cups are pretty sturdy. Fortseven why do you think they didn't do as well?

At the time, I did not allow for enough ventilation and the potting medium was not mixed with enough perlite and the cups were too big. For my level of experience at the time, I did better with pots designed for the purpose to learn what works. Joanne

When do I move my seedlings from my inside Styrofoam cups to my outdoor garden??

you do not want to move your AV plants to the garden if you have intentions to EVER bring them back inside. Too many chances for invaders in the house.

They're staying outside.