More and more of us are turning to wood burning to keep
warm. If we don’t mix the burnt ashes
with coal, there’s no reason why we can’t add them to the garden or compost
heap.
Wood ash is a great addition to the garden as it contains
potassium or potash.
Just as it does in humans, potassium regulates plants’ water
balance (so tissue is firm and juicy), and has a part in transporting food
within the plant and creating sugars and starches. Without enough, vegetables
are more vulnerable to drought, frost, pests and diseases. So adding this to
the garden is a great way to keep a balanced soil
Ash in the Compost
Heap
Wood ashes make a great addition to the compost heap. If you
have a lot add gradually over time as they are alkaline and raising the pH too
much will affect the bacteria and worms at work. It’s better to keep the ash in
a nearby container and sprinkle on a layer every so often.
If you tend to compost a lot of acidic material, such as
fruit waste, the ashes will help to keep the compost at a lower pH and reduce
the need to lime the vegetable plots at a later date. It could also help to dry
the heap and keep the pesky fruit flies at bay.
Wood Ash as a
Substitute for Lime
It is possible to substitute for the usual ground limestone.
However, home-produced ash isn’t a standardized product, which means its
content will vary, but I’d find that an enjoyable challenge. Hardwoods, for
example, generally produce more ash and contain more nutrients than softwood.
Bonfire ash is even more variable, because of the mix of plant tissue.
Like the potash content, the calcium carbonate content will
also vary (although it’s unlikely to contain more than half that of ground
limestone), so it’s a good idea to test the pH of your soil before adding the
ash and three to six months after, to check on its effect. It wouldn’t hurt to
check up on the potassium content while you’re at it. There’s no point in
adding potash to a soil that’s already high in potassium, as too much can
affect the plants’ take-up of other nutrients.
Where Not to Use Wood
Ash in the Garden
Being alkaline, wood ash obviously isn’t an ideal addition
if your soil already has a pH of 7.5 or greater. There’s no point in spreading
it around acid-loving plants such as blueberries or hydrangeas. Nor is it
recommended for areas where you intend to grow potatoes (much though they enjoy
potassium) as increased alkalinity can encourage the fungus, potato scab.
It’s also worth remembering that potash is extremely
soluble, so keeping it dry before use is advised (this includes before adding
it to the compost heap). Leave your ashes out in the rain and all the potash
will wash out and you’ll be left with a sticky and fairly useless sludge. If
you pile a large amount of ash in one area, you also risk over-liming that area
and damaging nearby plants.
Adding Ash Direct to
the Soil
Sprinkling ash straight onto the soil could deters slugs and
snail, until it gets wet though, then its effectiveness wears off. Some also
claim sprinkling ash in the drills when you sow carrots, and dusting it on
turnips to keep carrot and turnip fly away.
Spring and autumn are said to be the best time to spread the
ash around but as we accumulate most of it in the winter I think it can be
spread it around at other times whenever it’s available and you might as well
if you know you can’t keep it bone-dry. Root vegetables such as carrots,
parsnips, peas and beans (pods are a better weight and colour) and fruit all
appreciate potash.
Fruit
If you have only a
little potash, it should go to dessert apples, redcurrants and gooseberries
first, then to cooking apples, pears, raspberries, blackberries and
strawberries. Plums, apricots, cherries and blackcurrants appreciate a regular
sprinkle, but don’t need it so much.
