![Hardiness Map](http://lotsofplants.com/cdn/shop/t/92/assets/HZ_4-9.png?v=2462553944307201911721317691)
Shade hydrangeas prefer moist soil and regular watering during the growing season. For most, in order to obtain the blue flower color, apply 2 tablespoons of aluminum sulfate near the base of the plant. A rusty nail or coffee grounds will also increase the acidity of the soil which makes the flowers turn blue.