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

Tangled up in blue

Not all the plants have suffered in the cool, wet and windy conditions that prevailed here in the south of England for much of the spring and early summer. The blueberry plants, snug in their sunken pots of ericaceous compost, loved the daily soakings and produced a massive glut of fat indigo berries.

Blueberries need an acid soil (lower than pH5.5) and London clay on its own isn't nearly acid enough. So each plant occupies its own 35cm pot, and each pot is sunk into the soil so that the tops are at ground level. Sinking the pots reduces water loss, which is helpful since blueberries also like plenty of water. A yearly topping up of ericaceous (acidic) compost keeps them fed, and I also spread the shredded needles Christmas tree around the foot of the plants as a mulch in January.

This year, seven blueberry plants have produced around 6kg of fruit so far. I'm still picking enough each day to sprinkle over breakfast cereal.

But what to do with the rest of them? Blueberry muffins was an obvious choice since the homemade variety is invariably so superior to anything shop-bought. I used Nigella's recipe from How To Be A Domestic Goddess, also reproduced here: http://www.mumsnet.com/Recipes/i/1203-Blueberry-muffins.

But blueberry muffins will only make a small dent in the glut. In the past, I've made a blueberry tart with a blueberry-flavoured custard topped with the fruit, but the custard always cooks to a brown colour instead of mauve or deep purple - it's the blue of the blueberries mixed with the orange egg yolk. It's a real 1970s wallpaper brown and doesn't look very appetising. So this time, I went for a more conventional vanilla custard underneath the blueberries.

I wanted this to look like something you might buy in a French patisserie, and knowing my limitations, used a bought ready-made sweet pastry case.


Blueberry tart

185ml double cream
4 egg yolks
3 tbsp sugar
1.5 tsp vanilla extract

Pastry case
1-2 tbsp blueberry jam (see below), optional
Blueberries
Icing sugar

Heat the oven to 190 degrees. Take the pastry case out of its wrapping and place on a baking tray. Beat the egg yolks, cream and sugar together until smooth. Add the vanilla extract to taste and whisk well in.

Pour the custard into the pastry case and bake in the oven until set - about 25 minutes. Leave to coll, then spread a thin layer of blueberry jam (see below) evenly over the custard. Stud the top of the tart with raw blueberries - the jam helps to stick them to the top of the tart but isn't essential. Dust with icing sugar to finish off.

Blueberry jam
For the first batch of jam, I followed the recipe from the National Trust's Jams, Preserves and Edible Gifts. This calls for 850g sugar to 900g blueberries and was far too sweet for my taste.

For the next batch, I reduced the sugar and used 350g ordinary granulated sugar and 250g jam sugar. I also had 300g blackcurrants left over from harvesting the blackcurrant bushes and added these too for extra bite.

I left the blueberries to steep in the ordinary sugar, lemon juice (one lemon's worth) and a pinch of salt overnight. The following day I added the jam sugar, and boiled it up - it reached setting point in about 10-15 minutes.

Blueberries in kirsch
An incredibly simple recipe from Preserve, published by Hamlyn. For every 175g blueberries, use 50g caster sugar and 100ml of kirsch. Layer the blueberries and sugar in a sterilised jar, add the kirsch and seal.

Shake the jar every day until the sugar is dissolved then leave in the dark, unopened, until you want to use the blueberries.