There are many kinds of Hydrangeas available today. Maybe the plant breeders went a little crazy introducing new selections recently. The good news is there are a lot of Hydrangeas with new color options, smaller plants, and more flower power!
Nature Hills offers many options with some of the newest and the best.
There is one group of Hydrangeas with pink or red flowers that can be changed to blue or purple flowers by altering the soil pH. This group is called Bigleaf Hydrangeas (Hydrangea macrophylla) and the flower color can be changed by growing the plants in a lower soil pH.
There was a breakthrough with this species of Hydrangea that opened the door to growing them in colder regions. Then the plant breeders went to town introducing many new varieties with many new shades of reds, pinks, purples and blues. Some are mop head types with rounded flowers, and others are lace-cap flowers that are flat topped and the flowers open in a circle.
In general, these hydrangeas really prefer a slightly acidic soil higher in organic matter, mulch over the roots, and protection from the hot afternoon sun. Soil pH is the measure of alkalinity (higher) or acidity (lower) of the soil. You can buy pH test kits, or you can get soil from your local ag extension office to find out the pH and fertility levels - if you are interested in trying to change color at home.
Most of the production nurseries are growing these plants by treating the soil with aluminum sulfate or soil sulfur. The flowers that are produced in the lower soil pH are lavender, purple, or blue – or even a mix of these colors.
Some areas of the country naturally have a lower soil pH and those same Bigleaf Hydrangeas exhibit the blue and purple colors naturally. Maybe those same Hydrangeas are more pink and red at your home? If that is the case, then you can change those colors by treating the soil of your Hydrangea macrophylla.
Have you seen all the amazing selections available today? Smaller plants that re-bloom, and bloom for longer periods of time are leading the pack. Remember that only Hydrangea macrophylla types are the ones that you can change the flower color. In Hydrangea arborescens types (like the old-fashioned Annabelle types), flower color is not affected by the soil it is grown in. The same holds true for Hydrangea paniculata selections that are so popular, as well as Hydrangea quercifolia. These plants are not affected by the soil pH, but the flowers all do a bit of changing as they age and eventually dry and remain on the plants.
A simple way to change the color of your Hydrangea macrophylla selection is to add 1 tablespoon of aluminum sulfate mixed with a gallon of water and use that to water your plant throughout the growing season - a couple of cups each week or so. This simple method will help keep the soil pH lower and the blue and purple flowers coming on. When watering your plants with this mixture please be sure that your plant is not completely dry when you apply the aluminum sulfate as it could burn the roots. Keep your hydrangea roots watered and then apply the solution the next day to prevent any issues.