What's in a nut?

Dr Cath Price takes a look at Autumn nuts in this latest blog.

Every nut is a perfect survival capsule. The hard outer case protects the contents, which in turn provide everything the embryo tree inside needs to germinate and grow a good root so it can develop and make its own food.

All that goodness inside also makes it a perfect food for other creatures too, from mice and squirrels to hungry humans.

Botanically speaking, only some of what we call nuts really are nuts – the ones without a fleshy covering when they’re fresh, like acorns, hazelnuts, beechnuts and chestnuts.

Those like walnuts, pecans and almonds are called drupes. Nutritionally, though, they all have the same resources and benefits.

So what’s in a nut? Lots of energy, in the form of oil rather than starch. On average, nuts contain around 50% fat. They also have high protein levels and valuable dietary minerals and vitamins.

Most of our native nuts are edible raw, but acorns need to be processed (leached) to remove harmful tannins. You can do this by soaking the acorns in cold or boiling water, pouring away the water and repeating the process until the water runs clear. The acorns can then be dried, then ground up as a flour or used whole to make roast salted acorns or acorn brittle as a snack.

Pigs can eat raw acorns, and used to be fattened in oak woods to take advantage of the bounty (known as pannage), but acorns are poisonous to dogs, horses and cattle.

Grey squirrel with a chestnut (Gillian Day)

Wild creatures enjoy the nut harvest too – squirrels are famous for hoarding nuts for winter, and dormice for fattening up before hibernation on them.

The different ways small mammals nibble their way into hazelnuts can even be used as a surveying tool, to prove the presence of dormice in a woodland.

Nibbled Nut ID Sheet — Download this nibbled nut ID sheet here.

Nuthatches are named for their ‘nut-hacking’ ability, and woodpeckers will make a meal of them too. Jays suddenly seem more common in autumn as they collect acorns and bury them individually as a winter store. In Austria it’s believed that an acorn won’t grow unless planted by a jay, and the species is named eichelhähe (oak-planter).

All those calorie-laden nuts take a lot of growing, though, so many tree species don’t set seed every year. A good year for nuts is known as a mast year, and the trees synchronise seed production so that they all produce lots of seeds in the same year.

It is thought that this periodic glut of seed is a better policy than producing a smaller crop every year, as there will be so many nuts the nut-eating creatures can’t possibly eat them all and some will survive to grow.

The trees rely on animals to transport the seed away from the parent tree, hoping it will be ‘planted’ somewhere with enough light to grow, so they do need the services of the harvesters - the deep shade beneath the parent trees is not sufficient for the seedlings to develop – but the effort of production would be wasted if all the fruit was eaten.

So make the most of a mast year when it comes along, and get out there to do a little harvesting, and perhaps a little planting of your own. If nothing else, it’s a glorious way to enjoy the autumn woodlands!