It's a bit hard to tell from the photo but if they are square stemmed, leaves in opposite pairs and the top flower spike is leafless, it's wood sage (Teucrium scorodonia). I have not found any documented use for Wood Sage to date; if you know of any I'd be keen to learn of it.
Teucrium scorodonia is a PERENNIAL growing to 0.3 m (1ft) by 0.5 m (1ft 8in). It is hardy to zone (UK) 6 and is not frost tender. It is in flower from July to September, and the seeds ripen from August to September. The species is hermaphrodite (has both male and female organs) and is...
Should the above help? From my own experience in gardening, the bumbles enjoy it as one of those plants that revel in shadier conditions.