Oca/Corn/Huauzontle Polyculture — Still Seeking Low-Work Resilient Growing Systems.

In 2010 I posted here on interplanting Oca and sweetcorn. This year, I'm going a stage further by adding Huauzontle (or 'Aztec Broccoli') to that system. Huauzontle is a Chenopod crop producing greens and edible flower-shoots, historically an encouraged weed or tolerated volunteer in Central American maize fields.
Here are the three constituent crops ready to plant out on the 16th of June, Huauzontle on the left...

The Huauzontle seed came from Real Seeds, and was ridiculously fast to germinate; the seedlings were up in 48 hrs, so in future, I would direct sow with confidence. But this time they were multi-sown in cells a week or so after the corn.
The maize is Painted Mountain obtained in a seed swap parcel a few years back, (thank you Jayb). It gave 100% germination despite its age, in sowing conditions that were not really warm enough by normal standards. It's a many-coloured genetically diverse, heat and cold-resilient variety, bred to thrive in the Rocky Mountains. After last year's weather, I'm seeking resilient varieties! Two trays of commercial sweetcorn sown on the same day all rotted, thanks probably to chilly nights in the greenhouse. Not chilly by Rocky Mountain standards evidently.

The oca are a motly collection of leftovers stunted from being left in small cells too long.

Here's the scheme on planting day. That's a four foot wide bed...

 ...which has just been newly created by double digging, incorporating all available organic matter to full depth. Carrying through the resilience theme to the soil, there are even logs buried under there; anything to build up this silt soil, and give some water holding capacity.

Just four weeks after planting, quite remarkably the huauzontle was already providing greens and seed shoots for steaming, but proving too vigorous for this scheme, or at least is too thickly planted, and is shown here just before receiving a serious cutting back...

A few spare lettuce were squeezed along the edge too, and the paths mulched to limit water loss during the ensuing heatwave.

By the beginning of September the corn is ready to pick...

...and, despite occasional chopping back, the Huauzontle continued to be a bit too resilient. The Oca are definitely suffering from lack of light and water at this stage.

Here is the view of the bed on 31st October...

...The oca are expanding fast, fighting back, and flowering, with every indication of a decent harvest to be had by mid winter. The Huauzontle, disheveled by recent gale-force winds, has turned spectacularly red and carries a massive seed crop, so it seems likely that I, just like Central American peasants, will have it as a tolerated volunteer in seasons to come.
With wider spacing of the Huauzontle, this scheme would approach my ideal; no weeds had a chance, and the bed yielded well, but required almost no work input once created. And like the Forth railway bridge, it has redundancy — bits can fall off it, but it still works.

Main Oca Bed 2011 — If It Ain't Broke...

Last year's growing arrangement of Oca with cordon tomatoes was hard to fault, so I've just tweaked it slightly to optimise spacing and make it easier to manage this time round. Oh, and it's beetroot instead of lettuce for the quick-growing edge crop.

Here is Oca 'Dark pink', not yet at the sprawling stage, growing strongly between tomato 'OSU Blue', despite being subject to a medley of drought, high wind, downpours and hailstorms since planting out.

26/6/11

Observant readers might notice that there is incomplete fruit set on the tomato. I'm pretty sure this is due to the very dry conditions earlier in the season rather than any affect from the oca foliage covering the lower trusses.

The bed's timetable in detail:-

13th April. Cleared the preceding green manure crop (grazing rye). Tops hoed off with an azada, and removed, roots left in situ. Not dug.

14th April. Beetroot (plugs, sown 15th March) were planted out.
The tiny plants are just visible in rows 9" from the bed edge (centre foreground bed)...

I could have planted out the Oca at the same time, but last year they got a bit of frost damage around now, so no need to rush things as they are happily growing away in Root trainers at this point.

9th May. Oca and tomatoes finally get planted out. The Root trainer method seems like a success, and I'm sure this will give them a better start than using pots.

Tomatoes planted, Oca laid ready to plant, beetroot doing well...

That's Cheltenham Greentop on the left, and 'White' on the right.

The tomato supports are on 16" spacing, with 24" between the staggered rows. Incidentally this assumes using the UK conventional cordon growing method (side-shooting, and deleafing lower part of stem). If you use the American cage method I'd go for much wider spacing.

5th June. Full ground cover from the  Oca between the tomatoes, and beet down the edges (beetroot now being harvested).

10th June. Tomatoes are starting to crop. (Below) This is Katja, a Siberian variety, surprisingly the first to ripen. Thanks to Søren of Toad's Garden for the seed.

31st June. Oca stems over-reach themselves and collapse down at this time of year. This, along with deleafing the lower part of the tomato cordons improves ventilation and light access. The dappled shade from the tomatoes is enjoyed by the Oca, reducing stress in hot weather.

8th August. Tomatoes in full production.

1st October. Tomatoes on the wane, Oca ascendance.

4th December, tomatoes removed after the first light frost.

Tubers are swelling!

Harvest still to come!

Not the Three Sisters...

... not the traditional corn/climbing beans/squash polyculture, but a wilder and woolier version with slightly more obstreperous contenders. The Three Hooligans might be a more accurate name for what I have in mind.

Infant hooligans on planting out day (25th May)

'Hooligan 1' is Yacon,  Fiorella,  a Czech-bred quick maturing variety which I grew last year. I can confirm that it does indeed get a move on, and makes tubers long before standard Yacon. Each plant is liable to reach 8ft high by 9ft wide by the end of the season, and produce 10 to 15 pounds of edible tubers.

'Hooligan 2' is the Hog Peanut or Talet (Amphicarpaea bracteata). I don't have any previous experience of growing this, but it's reputation as a rampant reprobate proceeds it. I'm looking forward to trying the beans which form below ground. Thanks to Rhizowen for the seed, who was also thoughtful enough to provide the required specific inoculant to permit nitrogen fixing on the plant's roots.

'Hooligan 3' is admittedly a corn, as in The Three Sisters system, but this is Hopi Blue — a robust and highly variable variety, displaying diverse foliage colour, number of tillers, and ultimate height. It's usually described as growing to about 2 m but I think that must be in its arid homeland, as I have experience of it growing to more like 3m. Almost certainly there are different strains, which also might explain this difference.

But for a successful polyculture, it's as much about how you plant as what you plant. Here's a view showing the planting layout...

That's a 5 ft wide bed. Hopi Blue are more widely spaced than usual to admit light to the Yacon which are planted on the centre of the bed at 4 ft spacing. Hog peanuts are between the Yacon, and should climb to the light. You'll also notice a couple of rows of onions in there. They were planted back in March and could be a mistake, but they were a bargain and you never know, if they get a move on they could form an extra output.

A couple of weeks later the plants have settled in...

9/6/11

... and are still well-behaved, but for how long?

10/7/11

27/9/11 Corn ripening. Flowers on the yacon are a sure sign that tubers are forming below ground. And...

... the hog peanuts are producing their tiny delicate flowers.


16/10/11. The corn is harvested...

...and the corn plants removed. The yacon are about 8ft high and steadily flowering.

More updates later.

The All-Tuber Polyculture Mound, Part 2 ... Room for One More

A previous post showed how last year I used mound culture to grow a mixed tuber crop (Yacon, Oca, and Chinese artichokes) with the minimum of labour input.

Here's what's left of the mound... 

...untouched since last December when it was torn open to yield over 20 lb of harvest.  As I anticipated, there are plenty of volunteer Oca and Chinese artichokes appearing amongst the annual weeds this year, so I only need to add a Yacon to restore last year's successful system.

Less than five minutes after the previous photo...

... and the weeds are blotted out by a heavy covering of garden compost, and a pot-started Yacon is added to the top of the heap.

This much compost might seem like an extravagance, until one thinks back to the amount of biomass which was removed at harvest; here's the near hernia-inducing Yacon root as a reminder...

I'm also adding a fourth member to the polyculture. The Hog Peanut, or Talet (Amphicarpaea bracteata) is not a true tuber-crop, so stretches the concept slightly,  but will clamber and twine amongst the Yacon, potentially fix nitrogen, and hopefully add to the overall interest and subterranean yield of the mound with its wacky underground beans.

It's another self-propagator by all reports, so like the Oca and Chinese artichokes, it should be back every year...

...whether I like it or not.

Update photo, 1st August...  ...five foot high an' risin'.

Oca as Soil Fungicide?

I've previously proposed that Oca makes a good bicrop partner for outdoor cordon-grown tomatoes. This has been based on...  ...er, the fact that it seems to work well for me, certainly in terms of physical compatibility - space, light and soil utilisation.

Cue photographic propaganda:-

Now, I must say that when it comes to plant companion effects I am, if not actually sceptical, then at least untroubled by high expectations. Some traditional companion effects do not stand up to objective tests, and when they do, it is such a multi-factorial situation that it's difficult to say if the results will successfully translate to other growing conditions.

However going back to Oca and tomatoes, I recently found this paper which shows that water-soluble extract from Oxalis articulata foliage can suppress the soil-borne fungus Fusarium oxysporum, or as it is better known, Fusarium wilt, a particularly destructive and persistent disease of many crops, including tomatoes.

We only have to make a small speculative step to assume that other Oxalis species (including Oca) will contain the same natural fungicide, and by planting them with tomatoes there may be some protective effect  during the growing season.

Thinking more, this also supports my normal practice of leaving oca crop debris to cover the soil after harvest. Fusarium spores can survive in soil over winter, ready to infect any suitable host crops the following summer, but decaying Oca foliage may be releasing natural fungicide, to be rinsed into the soil by winter rain.

My outdoor tomatoes die from various things, usually late blight, but one year some, dutifully interplanted with French marigolds, died of fusarium wilt. Now all I'm saying is,  perhaps if they had been interplanted with Oca instead...

UPDATE 23/11/10
Lab tests reported here show that ocatin (a protein in oca tubers) suppresses fusarium oxysporum, as well as Phytophthora cinnamomi ('dieback' or root rot), and Rhizoctonia solani ('damping off' and brassica wire stem).
Of course, the fact that the tubers can protect themselves from some fungal problems is a separate issue from foliage anti-fungal properties, but interesting nonetheless.

The All-Tuber Polyculture Mound

In a quiet corner of 'my other plot' I'm trying another cultural method - a four foot wide mound with three different tuber crops grown closely together. I'm aiming for a low-maintenance easily-harvested dense ruck of tuberous productivity.

Unlike standard polycultures, a clear requirement for an all-tuber polyculture is that the crops involved should mature, and be harvested all at the same time, otherwise lifting one will disturb the roots of those remaining.
Oca, Yacon, and Chinese Artichokes together satisfy this criterion quite well, all normally being harvested after their top growth has been killed by frost.

I started in Spring by clearing the area of the previous Jerusalem artichoke crop (yeah, right!), and digging in a barrow-load of rough compost. This was more to improve water retention and aid soil friability (and hence make harvesting easier) than it was to boost fertility. On top of the mound goes one of my prized new variety purple Yacon, purportedly quick-maturing, but so far untried by me. It is certainly much more vigorous than my other 'standard' Yacon variety. Around this goes Oca, then on the outside edge are the Chinese Artichokes.

This little experiment could easily be scaled up to an informal linear raised bed (or 'lazy bed') if one wanted. It could even work on a commercial scale if suitable harvesting machinery was available.

With all the incorporated compost, thorough deep cultivation, and dense weed-suppressing foliage, this is also ideal as a once-and-for-all soil improvement method before turning ground over to no-dig culture.

Drought is the problem this season. All three crops are showing stress, but it will still be interesting to see what quantity of tubers can be got from this single square metre of ground.

Update 31/8/10

The drought has given way to a couple of weeks of pleasant showery weather. The soil moisture, no doubt helped by all that compost in the mound, has caused the Yacon to double in size. It is now seven foot wide and tall, topped with a lanky bouquet of flowers.
It is even suppressing a couple of late-breaking jerusalem artichoke volunteers, and I now fear for the productivity of the Oca and Chinese artichokes.
I either need a smaller Yacon, or a larger mound!

Update 1/11/10

The first air frost on 21/10 burned back the yacon foliage, but has not completely killed it. Under its protective canopy, the Oca plants have escaped damage, unlike those planted on open beds nearby.
A few days before the frost, I noted the yacon had grown to have a spread of nine feet!

Update 12/12/10
There has been freezing weather for a couple of weeks, and the plants are showing no sign of life. It's a dry day, so a good opportunity to exhume the contents of the mound.

First up is the Yacon. It's a big one! The Health & Safety Executive would have me use a hoist for this job, but after a bit of grunting I manage to get the crown in to a wheelbarrow solely by manual handling methods.

After washing, the useable tubers weigh in at 18 lb (8.2 kg), with another pound or two of small or damaged ones.

Delving around nearer the edges of the mound reveals the 'also rans' – a moderate scattering of mostly undersized Oca and Chinese artichoke tubers.

About 1.5 kg in total – which is as much as I can expect given that the plants have been camped under dense Yacon foliage for most of the growing  season.

CONCLUSIONS
This growing method was successful in terms of yield and low-labour, despite an unusually early frost. Next year it will be even easier; it will only be necessary to plant the Yacon, as there should be ample volunteer Oca and Chinese artichokes.

The imbalance in yield between the three crop species was caused by misjudging the vigour and final size of the particular variety of Yacon chosen. I mistakenly assumed it would be similar to the 'standard' Yacon that I have grown previously, and as a result the Oca and particularly the Chinese artichokes suffered from lack of light. However, a variety being too successful is a good fault, as they say.

It is an interesting and potentialy useful observation that the Oca were protected from the first frost by the Yacon foliage. Yacon, not being reliant on day length, can tuberise early, before sacrificially protecting undergrowing tender crops which have yet to fully tuberise. The partial defoliation lets through more light to ground level, and as long as there is not a second frost, the lower crops benefit.