County Court judge Richard Maidment said Michael Murphy's offending must have instilled terror in his victim.

Judge Maidment said Murphy felt embarrassed and ashamed over what he had done and claimed to have acted out of a misguided sense of loyalty to his de facto partner, Rachael Kilpatrick.

He said the gardener, Angelo Dinome, suffered a broken nose, chipped tooth and bruising to the face during his ordeal and it was not surprising the impact on him had had ongoing emotional consequences.

"The whole episode was an appalling and evil course of conduct on the part of all of those involved, including yourself," Judge Maidment told Murphy. "No wonder you're ashamed. You should be."

Murphy, 35, pleaded guilty to kidnapping the gardener, intentionally assaulting him and stealing $200 from him.

He was jailed for a total of four and a half years with a non-parole period of two years and nine months.

Prosecutor Sally Flynn had earlier told the court Mr Dinome was mowing lawns outside a block of units in Ferntree Gully when Kilpatrick invited him inside for a cup of coffee in early 2012. Kilpatrick was living with Murphy at the time and both were heroin users.

"Kilpatrick offered to have sex with the victim for $200, a price of $150 was ultimately agreed upon and they partially undressed and had sexual relations," Ms Flynn said.

"Afterwards, the victim returned to his gardening duties and went home."

Ms Flynn said that about a week later Kilpatrick robbed the gardener of $700 at knifepoint.

And on March 7 last year, Kilpatrick told friends Juanita Dunlop and Rodney Gosland that the gardener was "pretty cashed up" and would be a good target for a "quick money earn", Ms Flynn said.

Kilpatrick allegedly disguised her voice and used a different name when she rang Mr Dinome's home phone number to organise for him to clean up a garden in Elsie Street, Boronia, the next day.

Dressed in dark clothes, wearing black balaclavas and carrying backpacks with a spare change of clothes, Murphy and Gosland were hiding in bushes at about 7.45am before confronting Mr Dinome when he arrived, Ms Flynn said.

The two men allegedly stole $200 from Mr Dinome, bundled him into his own car and drove off before punching and kicking him and threatening to kill him. They left him in the car when it broke down in Chirnside Park.

Kilpatrick and Gosland are due to appear for a contested committal hearing in the Melbourne Magistrates Court in March on a number of charges.