Rahim Mohammadi, 40, of Goldsmith Row, east London, appeared at the Old Bailey via video link over the death of Lea Adri-Soejoko in February.
She had been strangled with a ligature and her body was found in Colindale, north-west London, at the allotment where she was secretary.
Mr Mohammadi was remanded in custody ahead of his trial in July.
A man has denied murdering an 80-year-old woman whose body was found in a garage at an allotment.