OTTAWA — A Toronto landscaper pleaded guilty to eight murders on Tuesday in a case that traumatized the gay community in Canada’s largest city.

The landscaper, Bruce McArthur, 67, was arrested a year ago and initially charged with killing six men, dismembering them and hiding the pieces in planters on the property of a client who allowed him to store tools there.

Additional remains were later uncovered in a ravine behind the house where he had transformed planters into graves.

A limited amount of new information about the killings was presented in court on Tuesday. Michael Cantlon, a prosecutor, said Mr. McArthur planned all of the murders, held some of his victims captive and killed others while also sexually assaulting them.