After returning from work in Toulouse for a week (it’s a hard life I know!), I was delighted to see the potatoes had grown to 15 cm in height and were ready for more compost.

As you can see, the charlotte potatoes (top) have shown much more growth than the pentland javelins (bottom). 

Just over a month ago, I posted about building  a trough and planting potatoes. As I mentioned then, keeping the potatoes topped up with compost encourages maximum underground growth and hence potato yield, similar to the way farmers mound around potato plants.

Here they are after topping them up a bit:

We put together a diagram which simplifies and sums up the whole process:

Efficiency

 I have been actively keeping an eye on costs and efficiency as these are very important to urban gardening. My early suspicions are that potatoes will prove best in both departments. The potatoes are cheap to buy, seem to do well in limited light, make good use of vertical space and will hopefully provide a good yield. I guess only time will tell!

What do you think is the most space and cost efficient crop for growing in tight urban spaces?