[Markw]

I am planning on having a go on making some joint  potato  and carrot planters with a difference for next year. I am planning on growing Nicols's and also sweet potato's with the carrots on top.

I have one question if someone could help me with, this is the soil area each potato needs for best return. I have been reading up on potato planter sacks and how people plant them some people put 4 in the bottom, some put 2 in the bottom and 2 in the middle and maybe one in the middle.

What I need to understand is how potato's grow . Do they all grow around the seed potato and and up to just below the surface of the soil and how far do they spread out under the soil. All it is about is getting the most potato's and carrots from the least amount of soil per square meter of surface growing area. Any advice or pointers would be most helpful

Many thanks
Many  thanks

[DD.]

This is how a typical potato grows:



Your main problem, as I see it, with what you intend, is not how they spread out underneath, but the size of the haulms of the spuds. These can easily spread out 18" or more in all directions and you need to well clear that distance before sowing any carrots. 

My spuds are planted in rows 2' apart and the halums end up touching and overlapping each other, totally blocking out the light to beneath them.

In my opinion, you would easily need a planter about a metre across, before you could even consider planting carrots at the very edge.

[Markw]

Thanks DD
It is complected !!!. The planter is set at 45 degrees and is terest, the carrots go in 2 gallon buckets on the top behind the top row. I use the back of the planter as a compost store to get the soil temperature up.
Tried it on some plants this year and it works very well, growing at 45 degrees reduces the floor surface area of the planter. growing in a terest the halums are at different heights as they are staggered. the whole planter is faced ,south the problem is the soil could get to hot
It has some very good advantages growing like this. it is made from old pallets
Thanks for posting the picture it gives me some idea on finishing the design.