The plant sale (vide jardin) in Trévérien is on 6th April 2014. It is always the first Sunday in April.
You will find some plants, bulbs, shrubs, seeds, gardening tools etc at a discount price. It is like a car boot sale but you will only find gardening things.
The location is great: it is only the canal only 20 min from Dinan in Brittany, France.