How to Dry and Store Walnuts

Dry walnuts immediately after hulling and washing. The target is about 8% moisture for in-shell nuts and 5% for kernels. Air-dry them in shade with good airflow, spread in a single layer – this takes 4 days or more depending on the weather. In a dryer, keep the air at 32–40°C (90–104°F) and never above 43°C (110°F). Well-dried in-shell walnuts keep for about a year at around 5°C (41°F) and 60% humidity; shelled kernels go rancid much faster and should be stored cold, dark and airtight.

Why Walnuts Must Be Dried

Freshly hulled walnuts are wet. If that moisture is not removed:

• mould grows inside the shell and the kernel darkens and spoils;
• the oil in the kernel breaks down and turns rancid;
• storage pests multiply;
• nuts lose weight later and buyers pay less for damp nuts.

The snap test: crack a few nuts at random and try to break a kernel in half. If it snaps cleanly instead of bending, and the membrane between the halves is brittle, the nuts are dry enough to store.

Air-Drying Walnuts at Home

• Dry in a shaded, well-ventilated place. Direct sun can crack shells and heat and darken kernels.
• Spread the nuts in a single layer on mesh racks or trays; do not dry them in deep piles.
• Stir them several times a day.
• Cover or bring them in at night and in rain – dew and rain undo the drying.
• Never spread them directly on soil; they pick up moisture and dirt.

Depending on the weather, air-drying takes 4 days or longer; in cool, damp autumns it can take a few weeks.

Drying Temperature and Kernel Colour

Raising the heat to speed things up is tempting, but high temperatures darken kernels and speed up rancidity.

• Never let drying air exceed 43°C (110°F).
• The ideal heated-air range is about 35–40°C (95–104°F); drying at 32–34°C (90–93°F) for around 20 hours is a common recommendation.
• Do not dry walnuts in a hot oven or on a stove – it spoils colour and flavour.

Drying a little longer at a lower temperature always beats drying fast at a high one.

Using a Walnut Dryer

Commercial growers dry walnuts in bins or dryers that blow warm air through the nuts; tonnes can be dried in a day or two.

• Load nuts into the dryer as soon as they are hulled and washed.
• Check air temperature with a thermometer and stay below 43°C.
• Make sure air passes evenly through the whole batch – deep layers dry unevenly.
• Ventilate the room so humid air is carried away.

How Long Do Walnuts Last? Storage Times

Dry walnuts reabsorb moisture in a humid store and go mouldy. They also absorb smells easily, so keep them away from onions, garlic, fuel, fertilizer and chemicals.

Tip: freezing hulled, dried nuts for 48 hours before sealing them in airtight containers kills insect pests and their eggs.

Why Walnuts Go Rancid

About two-thirds of a walnut kernel is oil (65–72% in good varieties), mostly unsaturated fats that react easily with oxygen. Rancid walnuts look darker or yellowish, taste bitter and smell of stale oil. Three things speed rancidity up: heat, light and air. Keep walnuts cool, dark and sealed.

In-Shell vs Shelled Walnuts

• The shell protects the kernel from light and air, so in-shell walnuts last far longer. Crack them as you need them.
• Once cracked – especially when broken into pieces – kernels can lose flavour within a few months.
• Store kernels in airtight jars or vacuum packs; vacuum packing is the best option.
• Keep kernels in the fridge, or in the freezer for long storage.
• Keep clear packaging out of the light.

Preventing Mould and Pests in Storage

• Store only fully dried nuts – one damp sack can spoil a whole store.
• Keep sacks on pallets or racks, not on the floor, with air space between them.
• Sort out wormy, cracked and empty nuts before storing.
• Codling moth larvae can overwinter in cocoons in stores; do not build the store right next to the orchard.
• Inspect regularly and screen doors and vents against rodents.

Mouldy kernels with grey-green patches should be thrown away.

Related Walnut Guides

• How to grow walnut trees: complete guide
• When to harvest walnuts
• Walnut tree yield and years to bear
• Is a walnut orchard profitable?

Frequently Asked Questions

How long does it take to dry walnuts?

Air-drying takes 4 days or more depending on the weather; in a dryer at 32–40°C (90–104°F) it takes about a day.

How do you know when walnuts are dry?

Crack a few and bend a kernel: if it snaps cleanly and the inner membrane is brittle, the nuts are dry.

Can you dry walnuts in the oven?

Only at the lowest setting with the door ajar, below about 40°C (104°F). Higher oven temperatures darken kernels and spoil flavour.

How should you store walnuts long term?

Keep them in the shell in a cool, dry, dark place, or store kernels airtight in the fridge or freezer.

Why do my walnuts taste bitter?

Bitterness usually means rancidity caused by heat, light and air. Poor drying or storage at room temperature for too long are the common causes.