Oak: Plant profile
Oak Tree, English Oak, European Oak, Pedunculated Oak, Sessile Oak, Dair Ghallda
Quercus robur, Quercus petraea & other Quercus spp.
Oak is native to Europe, north Africa and western Asia, though planted worldwide. Very common in the UK and Ireland.
Where to find Acorns
Acorns come from Oak trees growing in hedgerow, woodland and in parks.
When to find Acorns
Acorns are ripe in early autumn, when they start to fall down.
How to identify Oak
Oak is a large, deciduous tree growing up to 40m tall. It has wide-spreading, branches on a short, robust trunk with greyish-brown bark. Most oak trees have simple, lobed leaves,which are dark green on top and pale green beneath.Male flowers are on catkins and hang down, while female flowers are small and red and are located on short stalks called peduncles. The encased brown fruit is the acorn and resemble a nut.
There are hundreds of different species of Oak tree and Quercus robur and Quercus petraea are the most common in the British Isles. All of them are edible, but acorns from certain species may be extremely bitter.
All about Acorns
Oak is the most common woodland tree in the UK and Ireland; so much that it has been a national symbol of strength and longevity for English culture, heavily featured on folklore, literature and local history. The saying goes “Mighty oaks from tiny acorns grow” meaning that something great may come from a modest beginning.
Acorn is the nut of the Oak Tree (Quercus sp). 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 (Quercus x rosacea).
Medicinal properties of Acorns
The oak tree has a long history of medicinal use and it has been valued for its astringent properties. All parts of the oak, including wood, bark, leaves, acorns and galls, have been used for medicinal purposes.
Acorns are nutrient-rich and contain starch, oil, protein and minerals.
Culinary use and recipes with Acorns
The trees are all around us and are quite prolific; yet rare are the people who bother with acorns. The issue with the nuts is not their flavour but the effort involved in getting them processed, because they are naturally inedible to us humans. Acorns are packed in tannins; which is a compound that makes them astringent, therefore they must be processed or “leached” to make them palatable.
The nuts are very 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 that contains large amounts of protein, carbohydrates and fats.
Acorn flour can be used to make bread, pancakes and burger patties. Koreans eat dotorimuk, which is a jelly made of acorn.
Safe foraging of Acorns
The high tannin content in oak may irritate the digestive system. Leaching is necessary before consumption.
Ecological importance of Oak
Oak trees support more life than any other native tree species in the British Isles and Acorns are a significant food source for a number of small mammals such as mice and squirrel, and some birds, such as jays . A lot of insect species depend on Oaks too.
25 thoughts on “Acorn (Oak)”
In my area there will be a lot of beech acorns this year.
If someone could help me how to sell it, I would be very grateful.
Best regards: Charlie
How do they taste after leaching?do they taste like other nuts?
They are certainly nutty and a bit crunchy when cold-leached.
I don’t think they are quite like any other nut, perhaps closer to chestnuts than any other.
The second picture is Swedish whitebeam, not any species of oak. It would be very impressive to find an acorn on it.
You are right, I uploaded the wrong picture to the wrong post. Already fixed. Thanks for letting me know!
How long can I store them for before using and how best to store them. Can they be picked green to brown from the tree and left to ripen
1. How long can you store acorns? Due to their high oil content, acorns can go rancid over time, so don’t let them for long. Maybe up to four months.
2. How best to store acorns? Discard any damaged nuts, lay them flat in single layer sheets and dry in a dehydrator or radiator (They’ll dry faster out of their husk).
Afterwards, store the dried acorns in canvas bags or baskets in a cool, dark place.
Alternatively, you can brine or freeze them after hot leached. Store the acorn flour in a cool place.
3. Can acorns be picked green? I always pick them brown because they are already ripe and the flavour is developed, but I hear some people pick them green.
Thank you for your informative reply
Re storage Is your advice with shells on or without
It’s up to you. Although I find that drying acorns with shells on, make it easier to open them afterwards.
Hi, thanks for a great article. I collected a few acorns to try and have put them in water. I did a combination of cold soaking and hot soaking (just when I remembered to change the hot water), not boiled at all though. After a day or so they turned brown. Is this normal? When shelling them, one was already dark inside the shell, and I decided to discard it – sort of mottled – but that’s the colour these have gone now anyway.
I cannot say without seeing them.
Overly hot water could caramelise the nut and turn it brown. After shelling them, the exposed nut could oxidise and turn mottled if scrapped off.
Next time, I’d recommend you shell them before cold leaching, as it will take less time anyway.
Just try a few nuts at a time with different batches, different trees… until you get to know the process.
Hope it helps.
Thanks Alvaro, I’ll keep experimenting. I forgot to say I scraped the inner membrane off the nuts, following something I’d seen a guy do on youtube to make flour. He seemed to think it was part of the leeching process or had a lot of tannins in it or something, but I guess this isn’t necessary (and it would be prohibitively time consuming for a larger number of acorns).
Would acorns make a pesto taking the place of pine nuts?
Any nuts can be used to substitute pine nuts in a pesto recipe (including acorns), each of them providing a slightly different flavour profile to the authentic recipe.
Never tried acorns on pesto myself, but I am sure it’s good. There is only one way to find out… trying!
Alvaro, great post as always. As a keen forager I’m always reading, always learning and find your posts to be so very informative and your site a great resource. My thanks
Thank you very much, I really appreciate your kind comments.
As a child we were told the acorn can be processed but the process can be ineffective enough to cause painful sickness if such occurs. Adding , eat them if you want to but don’t say you weren’t warned. How long does leaching tannin take to be completed in your understanding ?
Ingestion of unwashed vegetables may cause e-coli poisoning. Certain uncooked edible mushrooms may cause stomach upset, as it may be the case of uncooked beans and potatoes.
All these foodstuffs are safe once you properly cook and process them. Same applies to acorns.
In this link, I explain the leaching process to make acorns totally safe and palatable: https://britishlocalfood.com/leaching-acorns/
Cam you please tell me when they stop falling from the tree? They hit the roof right next to my head every couple of minutes and I can’t sleep!!!!
Hi Leila, it may vary depending on species, age, genetics or environmental factors. I dare to say your nightmare will last for about 1-2 months, sorry!…
Thank you for this post! It’s amazing that all this food is around us and many, including myself, have no idea it’s edible. That’s why posts like this are very important!
I was wondering, once leaching the tannins out by soaking, would you say acorns are safe to eat raw? (without the shells).
Hi James, acorns are safe to eat after proper cold-leaching because you have removed the tannins. However, I would recommend using those for baking! Thanks for your support!
can you tell me if you pick acorns green or brown please?
Hi Alison, pick them brown. Green immature acorns are unsuitable for eating.
Do you have a recipe for the acorn sauce for game? I’d love to try it out, but can’t find a recipe on the Internet.