Monday, 14 June 2010

Early Sprouter, Early Flowerer.

Yesterday, amongst the Oca / Sweetcorn bed, I was surprised to see one of the Oca was flowering already. In my experience this is a couple of months earlier than usual.  Consulting my notebook, I see that the plant is one of a selection that I have tentatively labeled 'Real Seeds Red (Early Sprouting)', as it is the second generation of tubers to be earlier to spring in to life than standard Real Seeds Red.

Perhaps there is a connection - the plant is vigorous, and generally keen to get on with life, and will go on to produce early tubers. But I am realistic enough to look for other explanations. The plants suffered some frost damage after they were planted out, and it may have acted as a stimulus to flowering.  This would certainly be a beneficial trait at the end of the growing season - a 'set seed before it is too late' gene.
Alternatively, watering with dilute urine stimulates flowering, or then again it's just a freak occurrence.

It gives me a chance to practice identifying Oca stylar morphs. This seems to be mid styled.

Anyway, the act of flowering is forlorn in this case, as there are no suitable pollination partners available yet (EDIT ...or so I thought - see first comment to this post, from Rhizowen). I looked around with frustration and notice Creeping Woodsorrel (Oxalis corniculata), a cousin of Oca, growing as a weed in the next bed. It's flowering. The flower structure looks very similar to Oca's.  Hmmm...

... I'm knowledgeable enough to know that it shouldn't work, but ignorant enough not to be sure it's impossible. There's nothing to loose by trying it.

EDIT During the following two weeks, three more of the same variety flowered, but none of the other varieties. Curious.
I was joking previously when I mentioned Watering with dilute urine but these plants are benefiting from this feed intended for the interplanted sweet corn, and it's the only difference in cultural treatment which I can think of that could be a factor. Anyway, all attempts at pollination whether by other mid-styled oca, or by unlikely motley related species have been unsuccessful so far. I'm now watching out for any official legitimate pollinators coming in to flower.  Work commitments are making it impossible for me to regularly patrol the plot during the crucial period around midday when flowers open, so there's a fair chance I'm going to miss the vital moments.

On an unrelated topic, since I read up a bit on vegetable breeding, I seem to be noticing mutations all around me now. Anyone for a bearded strawberry?

Tuesday, 8 June 2010

Oca / Sweetcorn Bicrop

Various sources state that this is a traditional Andean cultural method, but I cannot find any description of the specific planting patterns used.  They may well have used alternate widely-spaced rows of earthed-up Oca with later-planted corn. But I think corn pollination might suffer from the wide spacing, and the unnecessary soil disturbance and labour does not appeal to me.
I want a method that will suit my no-dig 4ft wide beds, and I think block-planted corn with oca near the centre-line of the bed is going to be the most practical approach for me.

Back on the 25th April the preceding crop of grazing rye was hoed off and removed (for strawing strawberries). Small pot-grown Oca were planted out on the same day.

By the 17th May (below) the Oca are established, but looking very lonely. I never like to see bare soil at the best of times, but continuing cool weather has meant the delayed planting of corn, and the Oca have been on their own for longer than expected. I should have left some of the grazing rye crop-debris on the surface to shade my precious humus and reduce surface evaporation.

Spacing for the corn is the tricky bit. I have a theory that if I can get the corn to support the Oca in an upright position, reducing stem contact with the ground, and thus reducing stem tuber formation, the plants will  be forced to concentrate all of their energy into bigger tubers around the roots (see Tubers- big and few, or small and many), and Oca - Be Erect not Supine!). The corn will have to be reasonably close-planted to do this, but must be far enough apart to admit light to the Oca - a fine balance.

6th of June, the sweetcorn are ready to go...
...and are spaced on a grid of about 1ft across the bed and slightly more along the bed. The Oca sit on the same grid so that each is surrounded by four corn. Just visible are beetroot plugs added along the edges of the bed to complete a three-way polyculture, and utilise the extra light available at the sides.

Plants watered in, paths mulched, there should be no more work until harvest.

Just one week later (13th June), all three crops are putting on amazingly fast growth. Notice the unusually early Oca flower
By the 20th of June, just 14 days after planting the corn, the canopy is about to close. So far, the spacing seems to be working just right, and the weeds won't get a look in.
4th July (4 weeks after planting corn) Stand well back everyone!
Keeping a log with photos and dates really highlights how quickly crops grow in midsummer. The Cylindra beetroot are already of a useable size, the corn is waist high, and the Oca foliage is relentlessly advancing towards the edges of the bed.
We've had consistently hot sunny conditions for the last few weeks, and I think the Oca is probably benefiting from the partial shading of the corn.

23rd July. The corn is above head height and showing signs of flowering. Some beetroot have already been harvested, and the Oca is giving full ground cover to the bed.
Weed suppression is absolute.
With the continuing drought, I've been forced to water a few times, and strong winds flattened some of the corn, so they have been staked, but otherwise the bed has looked after itself just fine.

20th August. The corn is cropping. It's averaging two good-sized cobs per plant, so six per linear foot of bed. The beetroot have all been eaten.

14th September. The corn has all been harvested, and the plants cut back to admit more light to the Oca during the shortening days.

Update, 2010 Oca harvest here.

Wednesday, 2 June 2010

Oca - Be Erect, not Supine!

Oca plants start off fine and upstanding, but then they always over-extend themselves and flop over. The newly horizontal stems then send out secondary shoots, upright at first, but they too collapse if they get long enough.

Once day-length reduces to a certain critical point, new side shoots start to stolonate, heading downwards and forming tubers, at or just above ground level.

In Tubers - Big and Few or Small and Many? I made the observation that these tubers never reach the size of those that form wholey underground around the original planting tuber, and I speculated that preventing these stem tubers from forming might lead to bigger underground tubers.
I've since looked at photos of traditional Andean cultural methods. Oca is earthed up, but the ridges are much bigger than those commonly used for potatoes - perhaps two feet high - so big that the stems are held fairly upright even when the plants are large (have a look). Perhaps this is the main benefit of earthing up - rather that the supposed frost protection effect, or to 'encourage stolon formation'.
I'm guessing that the above-ground tubers won't form if the stems do not sense soil nearby. The plant's reserves will have to be relayed to the underground tubers, increasing their size, instead of being dispersed across all of those tiddlers that mostly end up as bird food.

As a simple test, I'll try a few plants growing up through a wire mesh cage. This should be enough to support the stems and maybe keep them from stolonating.

Let's see how it goes.

Here's the view on the 4th July,

...and on the 1st of September.

On the 21st October there was an unusually early frost, killing off other oca plantings, but this group escaped fatally serious damage, presumably by being above the coldest air.
It produced a reasonable crop (interestingly, with almost no tuber stems) but I had no other plants left to compare against.
If nothing else, this method allows Oca to be grown in a much smaller space than if they are allowed to sprawl.