Spuds in bags

[Szmiti]

As we have a relatively small veggie plot but some areas of narrow hardstanding (concrete) doing nothing alongside our and the neigbours garage, we'd like to try to grow potatoes in used compost bags. Anyone tried this, and how to know how many seed potatoes per bag .... seems obvious but assume it depends on size of bag ? What's the technique and what are the potential pitfalls (if any) ... read somewhere that should start with bags half full and then fill roll up and with compost if / when spuds seen on surface to avoid greening (like earthing up ridges) ?

[Jenny Green]

Yes, you've got the basic idea. I've done this with 3 seed potatoes a bag but you can probably put in just one and get the same yield. You have to poke holes in the bottom of the bags to create some drainage.
I usually put about 4" compost or soil in the bottom, put the potatoes on that then cover with another 4". Then cover with soil to the top of the leaves as they emerge about 6" above the surface. You continue to do this and roll up the sides of the bag until they reach the top, then let them grow on normally. Make sure the bags you use are impermeable to light.

[Monika]

I 've done the same as Jenny and it works well. The compost mixture I have used in the past is about half last year's growbag compost (from salads not tomatoes!), a quarter sharp sand and a quarter well rotted farmyard manure. It produces a good crop and the potatoes are much cleaner than in ordinary soil. The other advantage is that you can put your hand into the soft soil when you think they are ready for harvesting, proddle about a bit until you find the size of potatoes you want to harvest and leave the others to grow bigger.

[Szmiti]

Thanks for the advice - I'll certainly be giving them a try this year ...

[Lyn]

Yes, it's a good space-saving way of growing a decent crop of good quality spuds. Remember, though, that spuds-in-a-bag need copious amounts of water, without becoming waterlogged. As Jenny suggests, good drainage is essential. I just use multi purpose compost, and add a handful of crumbled dried comfrey leaves to the potting mix (I can't get manure very easily). As the plants grow, an occasional watering with a high potassium feed is beneficial for them.
Regards, Lyn