When I sowed tomato seed in late August, I used the rest of the peat pots I had, and put the rest in regular plastic seedling pots. I'd actually decided not to buy peat pots again after reading that peat is a non-sustainable resource. I did try loo rolls for awhile but found the seedlings growing in the loo rolls stunted and yellowing. Thinking it must be something to do with the chemicals in the loo rolls (they were recycled loo paper rolls, but still, I'm not sure what goes into them) I'd stopped saving those. Looks like the loo rolls may have something in common with the peat pots though, because the difference between the tomato seedlings in the peat pots and the plastic pots is extraordinary.
Annoyingly I forgot to take photos before I repotted the 'peat pot' tomatoes into plastic pots. This photo is from a few weeks ago.
And these photos are taken straight after repotting. The seedlings on the left - tall, green and healthy - are in their original pots. The seedlings on the right - stunted and pale - are from the peat pots.
Why? I don't know. I love these mysteries in gardening. Same sun, same seeds, same varieties - Reisenstraube, Black Russians and Brandywine. I keep the peat pots pretty moist, and inside a larger wooden container, so I don't think it's because they dry out faster. My husband suggested warmth - black plastic does attract and hold heat. I also noticed some millipedes harbouring in the peat pots, but I thought they only eat decaying matter so I wouldn't have thought they'd be the cause of the problem.
I'm not a big fan of plastic (see this to for one of many reasons why) but luckily Ceres Nursery in Brunswick has a pot recycling crate - where you can drop off any used pots and take whatever you need. It's always full of seedling trays and small plastic pots so I don't feel so bad about freecycled ones.
I'm hoping now that the smaller plants have been repotted they'll come good. It will be interesting to see how they progress in comparison to they bigger siblings. I'll update this post in a few weeks with a photo.