How to Make a Snowball Bush Blue
- 1). Apply aluminum sulfate, which adds aluminum and acidifies soil, or lowers pH. Start whenever you wish during the growing season. The color change won’t occur until the following season at the earliest.
- 2). Dissolve aluminum sulfate in water and use that to irrigate your snowball hydrangea bush, saturating the entire root area.
- 3). Use 1 oz. of aluminum sulfate per gallon of water, or 2 oz. in 2 gallons of water for a large shrub, every time you water. It’s easy to overdo it with aluminum sulfate.
- 4). Continue to water with aluminum sulfate solution the following year, and monitor flower color.
- 5). Cut back to monthly applications of aluminum sulfate when your snowball hydrangea is producing flowers close to the color you prefer, to maintain soil pH. This color maintenance system is imprecise, so adjust the sulfate-water schedule as needed.
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