Demand for green walnuts is so high, a north-east Victorian producer is turning buyers away.

About 10 years ago, Carol Kunert and Mike Burston from King Valley Walnuts, planted a decoy crop to try to outsmart the local cockatoos.

The idea was to keep the cockatoos off the main walnut orchard.

It didn't work. But Ms Kunert and Mr Burston did end up with an unexpected income stream.

"We'd planted this long line of about 15 trees, and we couldn't harvest them, because they were half way up a hill," Ms Kunert said.

"Then a few years ago, we thought we'd have a go at handpicking the green walnuts."

These days the producers get more orders than they can fill.

"For us it's a very small market, we usually only take between 30 and 40 orders a year," Ms Kunert said.

A green walnut must be picked at a precise time — before the shell starts to harden. ( Supplied: Carol Kunert )

"The orders close at the end of October and we fill them when we pick in December; people keep contacting us asking if they can get some, but we're oversubscribed."

Green walnuts are handpicked at a very precise stage in their lifecycle.

The green walnut is the fleshy part of the fruit that grows before the nut forms.

"So, you know how you have an apple, and then inside in the middle is your seed?" Ms Kunert said.

"On a walnut, it's the same thing. You've got all the flesh on the outside but what happens with the walnut is the seed [the nut you eat in the shell] grows bigger and bigger inside as the flesh gets smaller and smaller.

"So, the flesh is there to protect the nut, on the inside and so this time of the year it's all flesh."

The producers check the crop every week and will probably start harvesting in early to mid-December.

Ms Kunert said there were various recipes for green walnuts.

There is a Greek dessert called glyko karydaki (green walnuts in sugar syrup), pickled green walnuts often enjoyed with biscuits and cheese or in a chutney, and they can also be infused with alcohol to make walnut schnapps or the Italian walnut nocino (a red wine-based liqueur).

Harvesting green walnuts has its share of challenges.

Being soft and fleshy, the green walnuts must be kept cool and harvest time is during summer.

Ms Kunert said despite having more orders for green walnuts than they can fill, for her business, normal walnut harvest in mid-April is the more lucrative crop.

"Green walnuts are just a bit dicey," she said.

"Harvesting in December, when it's hot, if you're not careful it goes to a mush.

"I say to people who might have 10 to 20 trees — if you can't keep the cockatoos off, you lose the whole crop, and so it's actually a really good alternative for small hobby farmers as a market."