This H. 'Fortunei' type cultivar of unidentified parentage was originated by Carl Mack and registered on his behalf by Peter and Jean Ruh of Ohio in 2002. It is a giant size plant which grows about 31 inches high with a spread of around 43 inches. The leaves are medium green, slightly wavy, cupped and ovate shaped. From July into August, it bears medium lavender, funnel shaped flowers.

'Spring Grove' may have been sold as 'Mackwoods No. 37'.