From Whatscookingamerican.net. It is very important to use culinary grade lavender. Lavender from florist shops, craft stores, and most nurseries are not for culinary use and contain harmful preservatives and pesticides!
Note: if you are using an organic cucumber from the farmer's market or your own garden, then it is not necessary to peel it unless you want to. Most cucumbers from grocery stores have food grade wax which makes it necessary to peel them.
Slice the cucumber thinly.
In a large glass pitcher, beverage dispenser, or a clean and rinsed gallon milk jug (or any large pitcher), add the ice cubes, cucumbers, cold water, mint sprigs, and lavender. Stir.
Cover and refrigerate for at least 2 hours or up to 8 hours. The flavors will intensify the longer it sits.