I'm a beginner so my questions are very basic! When growing seed potatoes in a plastic bin, should I keep the lid on. Are the potatoes free from risk of frost or should I keep the bin in the (unheated) greenhouse? What organic fertiliser is best and easily available for this purpose? Can I plant them now?
Hi and welcome.
If you keep the lid on the plants will not get any light, so no. You can protect them with fleece if it looks like frosts are forecast. If you keep them in an unheated greenhouse that will give much more protection than if outside. Organic fertilizers such as blood, fish and bone meal or pelleted chicken manure are fine and once the tubers start forming a high potash feed (eg. Tomorite) will help.
It's a bit early to be planting them yet, even in a cold greenhouse. I'd give it a couple of weeks at least and it's a good idea to have the bins and the compost in the greenhouse to warm up a bit before you put the seed in.
Hello, and welcome to the forum.
This webpage should be helpful - Growing Potatoes in Containers
As Colin said, it is a bit early yet
End of March, earlier April will be when most people will be looking to plant
If you want organic only, use chicken pellets as Colin mentioned. Mix a handle full up with some compost prior to filling your bin
I use polypots and 25litre plastic pots
I however, will mix peat up with Vitax Q4
Check out this LINK to see
The only other piece of advice I would add to the excellent advice already posted is to check what variety of potato you are growing and are they "earlies, 2nd Earlies or main crop" as this will determine how long they will require to be in the container before they mature. Earlies are are usually 10 to 12 weeks, 2nd earlies 12 to 14 weeks and main crop can be up to 20+ weeks.
Hope this helps