PlantFiles: Giant Hyssop, Horse Mint
Agastache urticifolia 'Alba'

There seem to be at least 3 Monardas with the common name "Horse Mint or "horsemint." Monarda citriodora (also from Lamiaceae) with deep purple or lavender bracts, Monarda punctata, with white to lavender bracts, and Monarda fistulosa (pink to purple bracts.)

In addition, a true mint called Horse Mint is Mentha longifolia, which although naturalized in the US apparently came over from England.

If your horse mint does not match the Agastache, try looking under the Monardas or Mints.

An unusual white form of agastache. Poker spikes of innumerable white flowers stand out from dark green, fragrant leaves. Loved by bees. Easy to flower in first year.