Growing potatoes in 35 litre pots….

[Rhys]

I harvested my first two pots of maincrop potatoes grown in 35 litre pots today – they were harvested a bit early as there may be blight arriving in the garden, so better safe than sorry. In each case, 2 seed potatoes per pot was used in el cheapo MPC from garden centre with a smidgen of sphagnum moss peat and a healthy dose of Blood Fish and Bone at the start.  I also had treated the ground the previous autumn with horse manure as a top dressing, which was dug in prior to planting and the trench into which the pots were laid was also filled with some well-rotted manure also.

Harvest date was 17 weeks after sowing and 12/13 weeks after final emergence of plants after topping up the pot to the top. I used the Maria Thun calendar for sowing, feeding and harvesting but due to the drought and heat I’ve been watering most days (which may not have helped the blight situation with exuberant haulms making access for a watering can difficult. The pots have holes in the bottom part of the sides and roots grow out from there into the ground to scavenge for further water and nutrients.

Desiree: 5lb 12oz from 27 potatoes, with a relatively small difference in size between tubers, although the few big ones were up to 7oz each.

Picasso: 5lb 4oz from 38 tubers (8 were still micro), with a small number of very large tubers (>0.5lb) and several relatively small. It is noteworthy that Picasso emerged 1 week later than Desiree after topping up, so in reality had 1 week less of ‘growth’ than the Desiree plant, which may indicate that around 0.25lb a week/seed potato may be the bulking rate prior to dieback.

The best practicioners of this technique manage to get 9 – 11lb from 2 seed potatoes (occasionally from 1) but usually, they can get their growth period to be well beyond 20 weeks. Dan at http://www.allotment-diary.co.uk has done several videos over the past 3 years of ‘spud reveals’ where he even weighs his crop on camera to show you 9lb of King Edwards, Sarpo Miras.

All my potatoes were disease free.

As I’m by no means an expert, it does seem to be a reliable technique and experts can expect 2.5 – 5lb of first earlies from 2 seed potatoes, 5 – 7lb for 2nd earlies and 7 – 11lb for maincrop, provided that blight doesn’t intervene early.

So far as I can see, the great advantage of this technique is the higher density of potato planting you can do vis a vis ‘traditional’ methods. In effect, you can plant 6 maincrop potatoes across a 1.5m row (3 pots with 2 seed potatoes each) and either a narrower spacing (50cm) or the standard (75cm) according to taste. Thus, if you have limited space, you may be able to up yields compared to ‘farm spacing’.

From what I’ve heard and read, King Edwards, Sarpo Mira, Kestrel, Charlotte, Nicola, Anya, Pink Fir Apple, Golden Wonder all work well with this technique and it appears that Desiree and Picasso will too.

The economics are broadly these;

i. Capex of £4 a pot which should last 10 years at least.

ii. £2 per pot on MPC (more if you are filtering it to use for shows – probably double it), call it £2.25 if you include the Blood Fish & Bone and Tomorite feeds.

iii. 25p – 75p on seed potatoes depending on source, order size etc.

So in reality you are spending around £3.50-4 per pot including depreciation to generate your crop, whereas if you were growing in the ground, you probably only spend £1 per 2 tubers.

So at 5lb per pot, you need spuds to be >80p a lb to break even, dropping to 40p a lb if you get 10lb in a pot.

My take therefore is that the technique is most valuable if space is limiting, since you need to water more often in dry spells than for crops in the ground.

[Author]

Posts