Bruce McArthur, 67, was arrested last January and charged in the deaths of two men, and police subsequently charged him in six other cases.
Most of his victims had links to Toronto’s Gay Village neighbourhood. Many of the victims’ remains were found in plant pots on one property in Toronto’s Leaside neighbourhood.
Each of the first-degree murder charges carry an automatic life sentence, meaning he will not be able to apply for release until the age of 91.
His sentencing hearing will begin on 4 February, in which friends and relatives will be give impact statements, describing how the killings have affected their lives.
In court on Tuesday, Crown prosecutor Michael Cantlon described how McArthur had “staged” and photographed the victims, keeping mementos such as jewellery and a notebook.
He described all of the crimes as “sexual in nature”, adding that there is evidence he tied the victims up during the murders.
While many of the remains were buried in planters at 53 Mallory Crescent in Toronto, where McArthur worked as a gardener, others were buried in a nearby ravine.
McArthur had an agreement with the home’s elderly residents to store his landscaping equipment there in exchange for free lawn care, according to the authorities.
Police say they found a duffle bag with duct tape, a surgical glove, rope, zip ties, a black bungee cord and syringes in his bedroom when they searched his property, according to court documents.
They say that some of the victims were killed during a sexual assault or while being “unlawfully confined”.
The arrest launched a massive investigation that spanned Canada’s largest city, one of the largest such investigations in the history of Toronto police.
Investigators searched dozens of properties linked to the self-employed landscaper and looked into cold cases dating back decades.
So far, all of the eight victims except one had ties to the city’s Gay Village.
Many were immigrants from South Asia or the Middle East.
Members of Toronto’s LGBT community have criticised police, saying they did not take their concerns about the missing men seriously.
The first two alleged victims were identified in January as Andrew Kinsman, 49, and Selim Esen, 44, who both went missing in 2017.
Since then, police have named Skandaraj Navaratnam, 40, who disappeared on Labour Day weekend in 2010; Soroush Mahmudi, 50, reported missing in 2015; Dean Lisowick, 47, who is believed to have been killed in April 2016; Abdulbasir Faizi, 42, who disappeared in 2010; Majeed Kayhan, 58, who disappeared in 2012; and Kirushna Kumar Kanagaratnam, 37, who police believe was killed in January 2016.