Dunedin City Council events co-ordinator Marilyn Anderson said more than 500 crosses planted on Tuesday would stand in the gardens until Armistice Day.
Each cross bore the name, registration number and rank of a soldier from the Otago infantry killed in September 1916, Ms Anderson said.
Dunedin historian Sean Brosnahan said the crosses were planted on the anniversary of ''a very bad day for the Otago regiment at the Somme'', September 27.
''Three out of four companies of the 1st Otago Infantry Battalion were annihilated in an attack on the Gird Trench system that went badly wrong.
''When the 1st Battalion marched out of the line on September 28 it was reduced to just 113 men, less than a single-company strength.''
The battalion started the battle with about 800 men, he said.
Ms Anderson said the display was about ''remembering'' and ''honouring'' the lives of Otago men.
Direct descendants of a soldier remembered on a cross could contact the council about keeping the cross when the display finished, she said.
The crosses were supplied by the Fields of Remembrance Trust which supplied 693 crosses last year to represent Otago personnel who died in the war in 1915.
Dunedin RSA president Lox Kellas said the crosses provided a chance for people to reflect on the ''futility'' of war.
