By Zoonie
United Kingdom 
Potato growing in planter bags - feedback on current crop.
Hello there. I am a gardening dork, but learning, with what I have. Had some early dropping potatoes so have dug up some lovely red organics. Perfectly lovely looking but various things crop up:
-Given how much compost you later on top of potatoes in bags, how much do you think you should water them? I have a feeling some of the things listed below are because it was too damp.
-Should the seed potatoes end up looking like spent, floppy squibs (I think it's my seed potatoes that do)
-Really weird thing: clumps of compost which might have even looked potato shaped, broken apart to find entirely filled with grey, dampish mould. Quite a few clumps like that. No potato matter at all, just this def. not potatoes mould.
-Same thing as last year but scrubbed off so I'm assuming it's non harmful. Small bobbly growths on the outside of some potatoes, looking for all the world like really bad acne clumps! Is this normal? Can it be prevented?
My crop from this bag has not been particularly huge. Got several more bags to go but a little underwhelmed thus far. Are there any decent compost additions one should dig in for pots?
-Should I now just dump the compost or is it good for anything else if I energise it a bit?
Thank you from a mere klutz for your expert potato knowledge!
3 Jul, 2011
I'll try to answer your questions in order:
Potatoes need a lot of water, especially if they are in planters.
Yes the original seed potato having done its job rots away.
No idea about the potato shaped lumps - lack of water?
Your potatoes have scab, they are still edible just don't look as attractive. Try to make sure the pH of your soil, or compost, is between 4.5 and 5.5 - potatoes don't like lime.
The one and only time I tried growing potatoes in a bag rather than the ground I was disappointed too. But some folk do have success. You will need full sun and to be consistent with the watering.
You can put the spent compost on your garden but watch our for small volunteer potatoes growing that you missed when you harvested. Alternatively add it to your compost.
4 Jul, 2011