Nuts about English walnuts

Are you someone who likes nuts in your brownies or Christmas cookies? Have you ever wondered where those nuts come from or how they're grown?

You may know that lots of nuts grow on trees, and there are even orchards where farmers grow nothing but nuts. At the Alameda County Fairgrounds in Pleasanton, Calif., though, tasty English walnuts are harvested in the parking lot.

Nuts as well as shade

That's right, the whole parking lot is filled with walnut trees – at least where there aren't parking spaces.

The trees range in age from two to 35 years old, and they were originally planted to provide shade.

"They could have planted any tree for the shade but decided to plant a tree that could be harvested and generate some income," explains Ed Johnson, maintenance operations manager for the Alameda County Fair.

Two types of tree in one

The trees aren't just any old walnut trees, either. The branches produce English walnuts, but the lower trunks are those of black walnut trees.

Why? Because the English nut tastes great but its roots are susceptible to common diseases. On the other hand, roots of black walnut trees are tolerant of the local soil and pests, but the nuts are hard to crack.

To get the best of both trees, an English-walnut bud is grafted (attached) onto a black-walnut seedling.

Every year, workers at the fairgrounds harvest between two and eight tons of walnuts from the trees.

But not all of the nuts on the trees make it to the harvest. Some get picked along the way. Squirrels and crows love them, and, according to Mr. Johnson, the local people do, too.

Generally, the nuts are ready to harvest in October. A machine that looks like a forklift with a long handle grips the trunk and vibrates the tree. This shakes the nuts to the ground.

Workers rake up the fallen walnuts and place them in 5-gallon buckets, which get poured into 55-gallon drums.

The entire harvest normally takes place in just one week, depending on how many fairgrounds workers are available to help. (You never know what else may be happening at the fair during the week that the trees are ready for their shaking!)

After the harvest, it's time to send the 55-gallon drums of walnuts to be processed.

It takes plenty of work to get freshly harvested walnuts ready to eat.

When the nuts grow, they're covered by a thick, green skin called a hull. By harvesttime, the hull has turned a yucky greenish-black color, and it needs to be removed to reveal the tan inner shell of the walnut. Once the nuts are hulled, they also must be cleaned and dried.

For the nuts collected at the fairgrounds, this all takes place at Alden Lane Nursery.

Alden Lane has been processing walnuts for decades and used to be surrounded by walnut trees.

Now the trees have made way for houses, and just a few remain in the car park to provide shade and serve as a reminder of this area's heritage.

Kids'-eye view

On the day I visit, children from a local school in Pleasanton have come to the nursery to watch the processing equipment at work.

After a hayride, they get dropped off beside a barn, where they gather around a pit full of unhulled walnuts. Nancy Clifton from Alden Lane warns the kids not to pick up any walnuts.

"[The hulls] stain your hands for about three weeks," she says, "like a Sharpie [permanent marker]!"

Ms. Williams, the class's teacher adds, "That's why we don't pick them up in the playground."

The students nod. Their school is named Walnut Grove Elementary, and they know all about walnut stains.

Ms. Clifton points out the conveyer belt. The bottom of it is in the pit of walnuts, and the top goes into the barn. It carries the nuts from the pit up into the barn and dumps them into the husker.

The husker consists of a large metal cylinder that has thick brushes with sharp wire bristles inside.

As the nuts pass through, the brushes grind off their green jackets. Water sloshes through, too, to help keep the machine running smoothly. The water combines with the leftover husks to make a green sludge. This is collected and returned to the walnut orchard, where it's used as compost.

Next, the hulled nuts pass through the "squirrel cage" for their shower. This is a circular cage that tumbles the nuts around and sprays them with water. It removes any remaining husks.

Ms. Clifton turns the machines on. The kids cover their ears – the noise of mechanical grinding and nuts tumbling is thunderous.

The nuts then travel to a sorting belt. This is like a table with a moving top. As the nuts pass through, two people try to sort the nuts and make sure they're all top quality.

Once the walnuts are sorted, another conveyer belt drops them into the dehydrator. This machine is like a huge oven. It can take as little as 12 hours or as long as 40 hours to dry out the nuts. "You have to be very aware of when you start the dehydration process," says Jacqueline Williams-Courtright, the owner of Alden Lane. "You don't want to get up in the middle of the night to turn the machine off!"

If the nuts aren't dry enough, they will get moldy. If they're too dry, they'll taste rubbery.

Once they are dried just right, the nuts are stored in dehydration tanks that make sure no moisture gets back in.

On their way to your house?

Now the walnuts are ready to go to the Diamond Foods company in Stockton, Calif. There, they will be sorted again.

Some nuts will remain whole in their shells, while others are glazed, halved, chopped, diced, ground, or chipped.

Finally, all the nuts will be shipped to factories to be packaged and sold.

The same nuts that were harvested at Alameda County Fairgrounds and processed at Alden Lane may well end up in a cookie, in cereal, or as an ice-cream topping that you or your family eat!