He was the son of a merchant father. At the age of 18, he entered the novitiate of the Salesian Congregation in Sant Vicenç dels Horts (Barcelona). Alexandre wanted to become a Salesian religious but was unable to make his profession because his deafness prevented him from doing so. He always lived as a religious, because privately he consecrated his life to the service of God and his brothers.

A few years later, the novitiate was transferred and the community of Sant Vicenç dels Horts was closed. Alexandre was left alone for 28 years and was like the guardian angel who looked after the house and the garden. Alexandre was well known by all the people by the name of 'el Sordo'.

'The Deaf' lived an exemplary charity in the village, always ready to help people in need, and for this reason he was fondly remembered by all. He practised the Christian virtues with the simplicity of a saint. Charity in its two aspects, love of God and love of neighbour, was the rule of his life. His charity towards others manifested itself especially in the care of the sick, attending to them especially in their last moments so that they might die a Christian death.

Alexandre was humble and exemplary in fulfilling the commitments of a good Christian: constant in daily prayer, slow and pious in praying the Stations of the Cross, he was in the habit of praying the Rosary when on the move.

With great love for God and the desire for the salvation of souls, 'El Sordo' accepted difficulties and sought a mortified life: he always prayed on his knees in church; his food was very simple and poor; he slept on a board; he wore a large crucifix around his neck, which he never took off.

Alexandre had a good religious education and during the almost forty years he lived in Sant Vicenç dels Horts, he collaborated in teaching catechism to children.

'The Deaf' was a good sculptor, he decorated the courtyards of the Salesian House with artistic statues of religious themes, representing scenes from the Passion of Jesus. During the Civil War his works were destroyed, leaving only the monument of the tomb of Jesus.

In 1931 the house was reopened as a Salesian novitiate. For Alexandre it was one of the greatest joys of his life. Alexandre offered the Salesians all the money he had saved, which he had earned through his constant work and his spirit of poverty.

In July 1936, the Salesians were expelled from Sant Vicenç dels Horts. Only Alexandre was allowed to continue living in the house, as he was not considered a Salesian. The Revolutionary Committee, seeing the religious piety of 'el Sordo', looked for an opportunity to eliminate him.

On 17 November 1936, the Salesian Eliseo García went to Sant Vicenç dels Horts to visit Alexandre. The visit was the reason for the Committee to falsely accuse them of being dangerous conspirators. A patrol of militiamen went to arrest Eliseo and Alexandre. On the 19th of November they were taken in a car to the coast of Garraf (Barcelona), martyred and their bodies were thrown into the sea.

On Sunday 11 March 2001, Pope John Paul II proclaimed Alexandre Planas Blessed along with 232 martyrs for the faith.