Wood ash is an ideal source of nutrients for plant growth

Fiann Ó Nualláin looks at the benefits of open-air fires and how ash from untreated wood and clippings can be a useful replacement for fertiliser when it comes to encouraging growth in your garden.

Wood ash is an ideal source of nutrients for plant growth

A FEW weeks ago, I wrote about how I love to chop wood in January as a way to kick-start a mindful New Year and work out the Christmas kinks.

Thanks for all the lumberjack jokes — nothing grounds you more than a healthy Irish ‘get over yourself’ slagging.

And I may consider the calendar idea too if hard times fall. But there is always practical method to my madness and, apart from some cosy log fires in the nippiest month, I do it for the ash.

There was a time when ash was as valuable to gardening as farm yard manure. It was prized to improve both soil and compost fertility and in pest management.

I like old skills (that work) and I like old methods (that are effective) — so if there is a way to slow down and fully immerse in the garden then I will always opt for the push mower over the Flymo, or the scythe over the strimmer (unbuttoned to the waist and sweat beads running — that’s April’s calendar shoot sorted).

Using ash may not be as effective as modern chemicals but that’s the point — it’s a slower release, nonchemical resource. And resource it is — just think of all the woody debris from prunings and wind damage that your garden amasses each year and which the compost heap rejects.

Some of the modern chemical agents took their cue from the ash tradition when in the 18th century, “potash fever” became big business and the benefits of ash-derived potash (potassium carbonate) fueled agriculture and the fashion for landscaping across Europe and in America.

A lot of the product being derived from American expansion and deforestation to create more farm land, the excess –and there was plenty, sold on.

In fact, in 1790, so economically beneficial and essential to food and textile crop production was ash fertiliser that the then just newly-independent America gave its first patent priority to it — US patent number 1: “An improved method of making pot and pearl ash”.

The success of wood ash at that time as much as its potential now, lies in its effectiveness — it contains almost all of the 13 essential nutrients required for healthy plant growth — it is from plant origin after all. It is especially rich in potassium, magnesium, calcium, and trace elements.

That content of calcium et al made it popular as a liming agent to de-acidify soils and make the ground more amenable to vegetable production — today we are invited by commercial enterprise to lime with ‘garden lime’

(calcium carbonate) or ‘Dolomite lime’ (ground limestone — magnesium & calcium carbonate).

Of course chalk and calcified seaweed products are available some places.

Liming is best done in winter months rather than just prior to sowing or active growing. So a sprinkle of wood ash makes perfect sense at this time of year.

Large scale commercial manufacture and sale of wood ash lapsed when chemical fertiliser became popular in the 20th century — it wasn’t going to stay a viable business, as how many forests can regenerate fast enough to meet the demand and a bucket of chemical seemed more efficient than a barrow of ash to the moderns of the day.

But the moderns of today are embracing renewable energy and wood ash is a byproduct of some of that and so easily sourced.

How many of us use wood burning furnaces and biomass central heating?

How many have been seduced by Bloom or TV makeover shows to install a fire pit in the garden? How easy is it to save prunings and twigs until the end of year or chop a few logs in winter?

You are not going to speed climate change with a small bonfire or the gatherings of your fireplace. Chemical production is.

Wood ash is not only difficult for slugs and snails to crawl over but detrimental to other soft bodied pests.

It can be used just like eggshells or sharp grit to form a protective barrier around vulnerable plants. It actually draws moisture from invertebrates’ bodies and stops them in their tracks.

To be honest, I’d keep it as a soil amendment or additive to compost as it not only washes away easy but wet ash will produce some lye and salts harmful to the plant.

In higher does it is outright toxic. The barrier requires a layer (more lye and salt) while the amendments are sprinkled like fine lawn seed and easily ameliorated into the body of the compost heap or soil structure.

By applying it now to bare or lightly worked soil means the rains on the way will leech the negatives away and wash the positives in.

Adding to compost in thin layers along with greens and browns it will work its magic upon breakdown.

Interestingly, ash helps with the pH of compost heaps and if you have a wormery bin then it benefits any brandling worms there.

Earthworms like more acidic soil so if you are no-dig and fully reliant on the aerations and nutrient transport of your gardens wrigglers then liming needs to be weighed up and perhaps not considered an annual intervention.

No matter what, you should always do a pH test kit for the local garden centre before you lime.

What are the rules of using ash? Only use untreated wood, garden clippings, straw etc to make the fire and yield the ash. Those blue pallets won’t do at all. The ash is an alkaline product so wear eye protection and gloves when handling. Before applying pH test first.

Use in moderation. Lightly scatter — never drop in clumps. Great for veg beds but don’t sprinkle on your King Edwards or British queens as it can contribute to potato scab.

Avoid around acidic loving fruits such as blueberries. Don’t mix with nitrogen fertiliser as the chemical reaction is to produce ammonia gas. It’s a once, maybe twice, a year thing — not every time you empty the fire pit or grate.

Fiann’s tips

Soil preparation for planting can begin this weekend — some like to turn over the ground but I prefer to dig where possible, only breaking that rule if I need to break up compacted soil or attack waterlogging.

You can top dress with compost or farmyard manure, cover with a tarp and let the worms do the work of improving soil structure.

It is possible to plant rootstocks and deciduous shrubs in milder times/locations.

We are still in slow mode as less traction on soil this weekend less compaction to deal with in spring.

Best practice is tidy up and plan for the season ahead.

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