A lesbian couple are thinking about abandoning their home after a vicious hate crime.

Anti-gay slurs were scrawled on their house and car, and their business was left in ruins when an arsonist torched a packing shed on their property.

Juliet Leigh and Lindsay Curnow have lived in the seaside community of Mangawhai Heads for seven years, running a successful floral business, Blooming Bulbs, from their backyard.

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In their mid-60s, both say it's always been an inclusive community and their sexuality has never been an issue.

But two attacks in a week mean they're contemplating moving on and closing the business.

On January 9, a friend's son was playing with their puppy Lulu when he discovered the graffiti.

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They found seven crudely scrawled messages – five on their house and packing shed, and two on their cars.

The messages, written in thin black permanent marker, were an arrangement of the words "dike", "trash", "dirty" and "filthy".

Curnow says the hate graffiti makes her feel sick. "We rang the cops and they said 'send in photos'. I don't think they took it that seriously then."

The following Saturday they went out for dinner, returning about 8pm – just in time for their favourite TV show, Midsomer Murders.

They would not get to see it.

"I know I locked up carefully because of the graffiti," Curnow said. But during the first commercial break they heard a bang they thought was kids playing with fireworks.

Not long after, they heard a second noise – this time thinking it was a door slamming.

Seconds later, there was an explosion and they rushed outside to see flames licking the shed's inside walls.

The packing shed – which housed two cold-storage shipping containers, an office, packing boxes, and gardening products – wraps around the yard, is metres from the house and runs next to a tall wooden fence between two neighbouring properties.

"Juliet was rushing across the lawn screaming 'you bastards'.

"I was pretty worried about her because she is pretty intrepid and she was starting to try to put out the fire with our garden hose.

"There were insect spray cannisters, polyurethane stacking crates, tissues and cartons in there, so I knew it was dangerous," Curnow said.

Leigh said they were lucky the fire brigade was just down the street, that the wind blew the fire away from their neighbours, and that days before they'd felled two totara trees bordering the shed.

Northland fire safety officer Craig Bain said if the trees had been standing, the fire would have spread to the neighbouring houses.

"It took a bit of putting out. It was difficult for the crews to contain it."

A decontamination unit also had to be erected because a material containing cyanide is used in the manufacture of the shipping containers.

"There are definite signs that someone has broken into the place. It was deliberately lit," Bain said. "It's a real nasty, nasty crime."

Neighbour Nigel Boyd and his wife were woken by the explosion and got up to see "flames everywhere". The fumes were "terrible" he said, and he saw one fireman spitting blood.

"I feel sorry for the girls. My wife worked for them part-time. It's disgusting. Mangawhai is a decent town."

Blooming Bulbs contracts growers nationwide to grow bulbs it sells by mail and internet orders.

Curnow said they "work like the clappers" for three months of the year and employ eight people to help pack around 300,000 bulbs.

She estimated it would cost around $100,000 to remedy the damage.

"It would cost more than the business is worth to have had full insurance.

"The suppliers are lovely people," Curnow said. "We know them personally, and they've all said they won't hold us to the contracts. But that's quite a loss for them too."

Police believe the two attacks are linked and are appealing for information.

Curnow said she and Leigh would not feel safe until they knew who it was and why they did it.

"I want to understand. We'd like to know it's not a local, and so would the community."