Hugelkultur - composting in situ

I first read about hugelkultur at a serendipitously good time. I had just had to prune out damaged branches from both the plum and quince trees after a storm, and the wood was piling up next to the bonfire. Separately I was also trying to think of ways to irrigate the blueberries, housed in pots of ericaceous compost and sunk into the ground. At the same time, it was the start of the year and my perennial new year's resolution, to garden more sustainably and with less waste, was uppermost in my mind.

Hugelkultur is really a long - German for 'hill culture' - word to describe composting in place, which gardeners have been doing for generations, but layering the matter to be composted in a specific way to conserve moisture in the soil as well as providing slow-release nutrients for plants. 

It is also a good way to use woody waste - logs, brushwood, twigs - that might otherwise go on a bonfire, now that many of us are trying to move away from burning waste, specially in built-up areas.  

The photo at the top shows a finished hugelbed, planted up. They make an attactive garden or allotment feature in their own right; you could design a lovely curved hugel bed to add contours to your plot.

Constructing a raised bed using hugelkultur principles

1. Dig out a trench where you plan to build the hugel bed. Save the earth, etc, that you dig out, and if you're digging out turf, try to save it in blocks - you will need to replace it later.

Ideally you want to dig down to the water table, but 30-45cms is a good depth, the deeper the better. The trench should be wide enough to take good-sized tree logs, but not so wide that you won't be able to reach to the centre when it's built - no more than a metre. This will also give you room to bank up the sides gently.

2. Start filling the trench, first with the larger logs, branches, woody waste. If the wood has already started to rot a bit, then so much the better. Try not to use green wood which might start to sprout. The kinds of wood that you are likely to be cutting down or pruning on an allotment or in a garden such as ash, beech, birch, apple, pear, cedar and other conifers, are all suitable for a hugel bed. 

3. Pack the logs in as tightly as you can, even chopping them up a bit so they fit if necessary.   

4. The next layer to go on top is the brushwood, smaller branches, twigs, etc.

5. Next, pack into the trench any more organic matter you may have: straw, green leaves (not whole weeds), seaweed, if you live near the coast, mulch, leaf mould, grass clippings, anything tht might normally go on the compost heap.

7. Now turf the bed, the surface of which should now be at least at ground level if not slightly raised. This turf should in theory be the turf that you initially dug out of the ground to create the footprint of the bed. Lay it 'upside-down', ie, with the grass on the underside and the topsoil uppermost. This forms a firm base for the bed. 

8. Add a top layer of compost, about 8-10cms thick. You should now have a gently mounded raised bed, ready to sow or plant into.   

At this point, I have found that for purely practical reasons, my hugel beds have been more stable if I give them wooden sides as with a conventional raised bed. So they are not strictly orthodox, but the principles are the same.

How it works

The logs on the bottom layer absorb water, and once saturated, slowly release it, along with nitrogen and other nutrients as the logs slowly break down. The smaller branches and greeen waste break down more quickly into composted organic matter, feeding your plants.

The turf layer also breaks down, giving you a nice fine topsoil tilth to plant into. The top compost layer gives you a good starting point. 

Hugelkultur - pros and cons

+ sustainable and inexpensive - uses readily available - and free - materials;
+ provides slow-release nutrients for plants;
+ as the woody materials and organic matter breakdown, the process generates heat and warms the bed, giving you better germination and extending the growing season;
+ reduced need for watering.

- labour-intensive to set up and build;
- benefits may not be apparent the first year as your hugel settles down and continues to absorb nitrogen;
- banked sides may need support.

Having tested this out on the blueberries, last year I built a second hugel bed for the blackcurrant bushes grown from cuttings taken the previous year. Once everything was in situ, we then went through a three-month drought in the summer of course. The plants in the new hugelbed struggled a bit  - they were very young cuttings, after all, but in the established blueberry bed, I managed to get away without having to water them at all, and they survived.

Further reading

https://www.permaculture.co.uk/articles/the-many-benefits-of-hugelkultur/ - The Many Benefits of Hugelkultur

https://www.growveg.co.uk/guides/how-to-make-hugelkultur-beds-for-growing-vegetables/ - Growveg.co.uk

The good, the bad and the puzzling - the year at the allotment

It's been a mixed year in the kitchen garden, with unpredictable successes and failures. Last year, it was easy to see that the long heatwave at the beginning of summer would be good for tomatoes, chillies and sweet peppers; this year has been much more unsettled.

There has still been plenty to celebrate. About six weeks ago, the bare earth container which holds the saffron crocus bulbs, started sending up little shoots, and for the last month I've been carefully tweazing out bright red stigmas to store as my first proper saffron crop.

Also coming good for the very first time is the fennel, a crop that has tended to bolt in previous years. I think the consistently wet autumn helped deliver steady moisture to the developing plants and produce some lovely crisp swollen stems.

Stalwarts that didn't disappoint included the globe artichokes: the plants, once established, produce multiple buds between May and July, then, after a rest in high summer, start sending up new buds again in September. We are just finishing them now.

Potatoes were terrific again this year: beautiful Lady Christls like unblemished hens' eggs in June, followed by delicious pink-skinned Rosevals and a long season for the maincrop Pink Fir Apples.

The weather was very slow to warm up in spring, which meant that chillies, peppers, tomatoes and aubergines couldn't go outside until much later than usual, and the seedlings stayed tiny until June/July. The sweet peppers, tomatoes and aubergines caught up quite quickly once they were finally planted out in the polytunnel and greenhouse (and the sweet peppers happily went outside); the chillies on the other hand, are still mostly green and I'm not sure the Carolina Reapers will ever fully develop.

The outdoor tomatoes fruited late but then they all fruited at once. We had about a month until the blight arrived at the start of October and then of course the plants were all gone over in the space of a few days. The greenhouse plants normally keep going until December, given mild enough weather outside, but having picked a load of little Black Cherries and the last few San Marzanos last week, I doubt we will get any more now.

Tree and soft fruit yields were similarly mixed. The red, pink and blackcurrants all fruited reliably but the whitecurrant bushes produced significantly fewer berries. I managed to net the cherry trees in good time (for once) and enjoyed a good cherry harvest. One day it would be nice to save some to make jam, or liqueur, but they are a bit too delicious to resist eating straightaway.

The quince tree, normally so prolific, only set four fruit this year. I think this may well be because we gave it its first proper pruning last winter. There was certainly plenty of blossom in late spring. And the pear trees nearby were so laden with fruit that I was giving away carrier bags full of fruit for a couple of  months in late summer. The perpetual spinach all bolted and I heard similar tales from other allotmenteers. The winter radishes, so plentiful in 2018, are this year still tiny and showing no signs of plumping up so far. We will just have to hunker down with the parsnips, beetroot, oca and yacon over the winter.

Grow your own - saffron

They say that saffron is the most expensive spice in the world, gram for gram.  Historically and indeed in the present day, it is much-prized for the golden yellow colour it adds to food or cloth, and for its warm sunshiney aroma.

Its high price by weight is partly because the saffron threads barely weigh anything: you need around 450 filaments to yield a single gram. It's also labour-intensive to harvest: the three long red stigma (below) are the parts of the flower that are picked and all saffron is gathered by hand.

Saffron originated in the Eastern Mediterranean, probably in Iran, which remains the largest producer of the spice in the world today. While it likes the bright Mediterranean sunshine, saffron grows perfectly well outside in the UK given a sunny position. It's also an attractive, with pretty striped mauve flowers, golden yellow anthers and the distinctive red stigmas.

You cannot just harvest any old crocus, however: not all crocus stigma are edible and some are poisonous. You need the long red filaments from Crocus sativus, or saffron crocus. It's an autumn-flowering variety which lies dormant for much of the rest of the year.

For that reason I grow mine in a large container, an old discarded water tank. If I had them in the open ground it would be all too easy to let the area become overgrown with weeds, or, worse, to forget about the crocus and start trying to grow something else in the space. 

Growing in a container also means you can ensure it's the in right place, which in this case, means the sunniest spot on the allotment but also one that is fairly sheltered. The saffron crocus bulbs like to bake all summer long before throwing up leaves and flower buds in September/October. They also like well-drained soil: easier to control in the container which has gravel lining the bottom, then layers of multi-purpose compost before a surface layer of topsoil.

Each bulb, or more accurately, each corm, will throw up one flower in a season, so you need plenty of plants to start off with. The corms will, however, divide in following years, so your stock should increase so long as the plants survive. 

The bare corms are generally available in mid to late summer. Plant each one about 10cm deep, pointy end facing upwards, and leave 15cm or so between them. You may well have to protect the bed from birds and squirrels who like to dig the corms up. I initially thought this would only be an issue while the bulbs were establishing but it turns out that they will happily dig for crocus corms at any time. So my plants grow through black narrow mesh netting stretched across the top of the old water tank and stapled into place. 

Once planted out and protected from foragers, you can pretty well leave them alone. They're perfectly hardy in a UK winter. I got a few flowers to harvest in my first year, but in year two they started producing much more prolifically. The leaves die down completely over winter so your saffron bed will be bare throughout the summer until the shoots start poking through the soil surface again in August/September.

Once the flowers start to come, you should harvest while the red stigmas are just showing, and on a dry morning: in the wet all that lovely golden pigment starts leaching out. Carefully pull them away at the base - this, finally, is where I have found a use for the teeny-tiny tweezers in my Swiss Army knife.

The threads need to dry out before being stored for culinary use. Optimally, this should be done in a warm place, even over gentle heat - Aga owners have an ideal saffron dryer. The rest of us can use the airing cupboard. Once dried, the saffron can be stored in an airtight container such as a small jar, in the a dark cool cupboard, and a pinch used for flavouring paellas, sauce, rice and so on as needed.

Saffron crocus corms available from Farmer Gracy, Suttons and J Parkers, among others.