Oak is the most common woodland tree in Britain. It has been a national symbol of strength and longevity for centuries, dubbed as the Royal Oak. The saying goes “Mighty oaks from tiny acorns grow”.
They are all around us and are quite generous producing nuts. However, they are not commonly regarded as regular nuts and are left to rot, as people tend to think they are not edible. Sometimes the problem with acorns is not their flavour but the effort involved in getting them ready to eat.
Description and species
Acorn is the nut of the oak tree (Quercus sp.) in the beech family Fagaceae and is the largest of the British native broad leaved trees, commonly found throughout deciduous woodland in warm temperate regions.
The tree can grow surprisingly big and are easily spotted by their wavy dark green lobed leaves and their characteristic egg-shaped nuts with beautifully crafted little hats on top, known as cupules. Each acorn takes 6-20 months to mature, turning from pale green to brown when ripe.
Sometimes you might find woody tiny balls stuck to the branches, making you confused. These are known as ‘oak apples’ or galls, made by wasps to develop a safe refuge for the larvae. These of course, are not edible.
There are two native species in Britain; the English oak (Quercus robur) and Sessile oak (Quercus petraea). Both of them have slight differences and often hybridise in the wild, being known as (Quercus x rosacea). They all produce edible acorns that require some processing.
Notes on edibility
Acorns have played an important role as a source of food in the past. They have been eaten in ancient civilizations like the Greeks or Iberians and became a staple for Japanese troops in World War II when rice and flour was scarce. In the same context, they were used to make a coffee substitute for German and Swiss troops.
Despite their extensive use in the past, acorns are regarded as famine food nowadays, with the exception of Native American Indian communities or Korea, where they still remain a popular ingredient used in acorn jelly and noodles made from acorn starch.
Lately, it’s starting to regain popularity among foragers, as all parts of the oak can be used: leaves, bark and nuts, which help to infuse new flavours and aromas as an ingredient. That is the very reason why oak wood is popularly used for making the barrels to mature wines and whisky.
Acorns are a sustainable and local food resource. They are nutritious and provide a complete vegetable protein, the starch, which is the toughest thing to forage for. Nutty and sweet, they provide an alternative gluten-free version for regular grain flours with large amounts of protein, carbohydrates and fats.
However, acorns are naturally inedible to us humans, as they are packed in tannins, a compound that makes them astringent and bitter, causing stomach upsets. Therefore, processing is required to remove the tannins before eating them.
Acorn grubs (Curculio sp.) are a short legless grub found often in acorns, especially if picked from the floor. They are said to be edible raw or cooked and taste soft and butter, but never tried. I think I am bit squeamish.
Foraging in season
You will not have any problem finding an oak tree, as it is the most common tree species in the UK, especially in southern and central British deciduous woods. They are seen in open countryside, alongside hedgerows and in parks.
Acorns can be picked in autumn, just before the fall of leaves. They are easily picked with no effort and it is advisable to keep your bounty in mesh bags, as acorns can get mouldy in plastic bags. Avoid any acorns that appear with any hole or blackened, as they may contain grubs.
For that reason, it’s better to pick acorns from the tree, avoiding the ones from the floor. That said, it’s not a really bad idea to pick off the ground after a windy day, as they are easy picking.
There are some considerations you need to bear in mind: oaks don’t produce acorns until 20 years old and don’t produce full crops every year, as acorns take a couple of seasons to mature.
Storage and processing
Acorns do need processing before eating in order to remove the bitter tannins. Please follow my instructions on leaching here.
Acorns have a high oil content and therefore can go rancid over time. It is advisable to store them in a cool dark place in an airtight container. Alternatively, they can be frozen or pickling, especially after hot leaching.
You can also process the acorns to make a roasted coffee substitute: just place the nuts in boiling water until soft and allow cooling. Chop the kernels into pieces and roast until slightly brown, then grind up into granules and roast again. Voilà! The powder is ready to use in a cafetiere in the same way as normal coffee.
Culinary uses and recipes
Acorn is mainly used for making flour to use in different recipes. Korean cuisine feature acorns more than any other, using flour to make dotorimuk jelly or dotori guksu noodles. However, acorn flour can be used 50-50 with wheat flour to bake any standard recipe: have a look at my acorn bread, acorn pancakes.
Acorns are quite nutty and you can use whole nuts and chopped pieces to substitute any standard nut recipe. Some ideas are: peanut brittle, peanut butter, chocolate spread, nougat, chestnut puree or almendras garrapiñadas. The sky is the limit.
There is no reason why you cannot add them into a stew in place of beans, pick the acorns in brine (just follow pickled olives recipe) or add flour to a creamy mash potato to lift in flavour. Alternatively, acorn sausages and burgers can make an excellent vegan alternative to the ‘real deal’.
Acorns aside, tree bark can add a distinctive touch to your BBQ and oak leaves can make liquours using rum or vodka.