Althea officinalis, Marsh mallow

Hardiness: Zones 3 to 9
Plant type: Herbaceous Annual
Height: 3-6ft
Spread: 2.5-4ft
Sun: Full sun
Water: Medium to wet
Bloom time: July to September
Bloom color: White, pale pink
Soil: Moist, fertile soil. Tolerates clay and wet soil

Notes:  In ancient times, the roots were cooked with honey to create a sweet confection and medicine. These treats are the precursors of modern, commercially available marshmallows, although they no longer contain marsh mallow root extract.

More information on this plant here.