Herb s-mashed this gardening challenge out of his Southern Highlands veggie patch

Family rivalry has taken on a sweet new meaning for gardener Herb Moule.

The patriarch of the Moule family in the NSW Southern Highlands has dug deep, to reveal, gardening victory over his two sons.

And the keen veggie gardener says he owes much of his success to COVID-19 isolation.

Herb from Willow Vale and his two sons - one living in Wollongong, the other in Woy Woy - decided to set a family challenge in spring 2019.

The aim was to see who could grow the largest sweet potato.

Well, after more than six months of careful nurturing, Herb has earned both bragging rights and a sweet option for several baked dinners.

In fact, it would be fair to say that Herb has s-mashed this potato competition.

Herb has proudly grown not, one, but two giant potatoes - a white and a red.

He said the white sweet potato weighed in at 1.78kg and measured an impressive 36cm long.

"The red is a little shorter, but is fatter and weighs 1.82kg," he said.

"The biggest sweet potatoes grown by my sons were about 600 grams, which is a normal size."

The 79-year-old green thumb said he had been a veggie gardener since his teens and this year's success growing sweet potato had been his greatest surprise.

"I've done well growing tomatoes, spinach and a variety of other vegetables," he said.

"This was the first time I had tried growing sweet potato and I wasn't disappointed. I will definitely be doing it again."

Herb said he planted the sweet spuds in late spring in a raised garden bed.

"It was a little late, but they still shot off like a gun," he said.

He said that good soil and fertiliser, moisture and plenty of attention were essential.

"I fertilised with blood and bone and Seasol every now and then, and I made sure the soil was kept moist," he said.

But the secret to Herb's success may well have been as simple as a little conversation as he said he gave them "plenty of attention."

"We've been in isolation for the last few months. I had to talk to something, so I talked to the spuds," he said.

And his gardening care has gone right down to the wire to ensure he won't be disappointed by the flavour of these giant veggies.

"The trick is to harvest the spuds soon after the leaves have gone black and died," he said.

"This is usually within a couple of days of the first frost, which turns the leaves black. You have to cut off the leaves when this happens otherwise they can send a sour juice to the potato.

"You also have to dig up the vegetable within a couple of days of the leaves turning black."

Digging up the spoils of his gardening success also required careful consideration by Herb.

"I had to dig deep to make sure I got them all, they grew well down in the soil, further than I expected. About 600cms deep in the garden box," he said.

Herb and his wife, Marcia, are now looking forward to dining on several sweet feeds. The preferred cooking option is baked.

"Baked sweet potato is the best way to go," Herb said.

This story That's not a sweet potato, THIS is a sweet potato first appeared on Southern Highland News.