Learn how to grow hydrangeas that bloom colorful flowers from summer into fall
With immense flower heads, hydrangeas flaunt an old-fashioned charm that is hard to resist. Unrivaled in the shrub world for beautiful flowers, these elegant plants are easy to cultivate, tolerate almost any soil, and produce abundant blooms. Colors beguile with clear blue, vibrant pink, frosty white, lavender, and rose blossoms—sometimes all blooming on the same plant.
About Hydrangeas
Hydrangeas are excellent for a range of garden sites from group plantings to shrub borders to containers. Varieties abound and it seems every year breeders present us with even more options, and gardeners’ expectations of bloom size and color are boundless. Hydrangea care is largely low-maintenance, making growing these colorful shrubs a good choice for new or experienced gardeners. But did you know that the color of the flower is influenced by the acidity of the soil? We will explain how you can change your flower color below.
When to Plant Hydrangeas
Plant in spring after the last spring frost or in fall before the first fall frost. See local frost dates. Plant before the heat of summer arrives.
Where to Plant Hydrangeas
Most hydrangeas will thrive in fertile, well-draining soils that receive plenty of moisture. Add compost to enrich poor soil. Flowering plants have a special need for phosphorus and potassium to realize their blooming potential. A combination of Dr. Earth Organic Fertilizer (shown below) and Bumper Crop Organic Soil Builder will provide these nutrients and encourage blooms on plants. Continue to fertilize by sprinkling a teaspoon of Dr. Earth fertilizer around the base of the plant. Repeat fertilizing every other month. Generally, hydrangeas prefer partial sun. Ideally, they will be given full sun in the morning, with some afternoon shade to protect from the hot midday sun. This is especially true for the Bigleaf hydrangea (H. macrophylla), which is prone to wilting. Some varieties are more tolerant of full sun. Space hydrangeas anywhere from 3 to 10 feet apart, depending on type.
How to Plant Hydrangeas
Dig a hole as deep as the root ball and 2 to 3 times as wide. Set the plant in the hole and fill it half full with soil. Water. After water is absorbed, fill the rest of the hole with soil. Water thoroughly again.
Pink hydrangeas are especially associated with genuine emotion because their shape resembles a beating heart. Because of this they are well-suited for special occasions and celebrations.
Hydrangea Care
For the first year or two after planting and during any drought, be sure hydrangeas get plenty of water. Leaves will wilt if the soil is too dry, and flowering will be hampered by a lack of water. If your soil is rich, you may not need to fertilize hydrangeas. If your soil is light or sandy, it’s best to feed the plants once a year in late winter or spring. We recomend Dr. Earth Organic fertilizer for Acid Loving Shrubs.
For new plantings: before you plant, add 2 cups per 1/2 cubic foot (about 5 gallons) of soil that will be added to the planting hole. Once planting is completed, add an additional 1 cup around the plant and mix into the soil. Water thoroughly.
For established plants: Use 2 cups for every inch of trunk diameter (measured at 4″ to 6″ above the soil line). Work into the soil gently inside of the drip line. Water thoroughly.
When to apply Dr. Earth: Every 2 months throughout the growing season. Be careful–too much fertilizer encourages leafy growth at the expense of blooms.
In the fall, cover plants to a depth of at least 18 inches with bark mulch, leaves, pine needles, or straw. If at all possible, cover the entire plant, tip included, by making cages out of snow fencing or chicken wire, and loosely filling the cages with leaves. (Do not use maple leaves, as they tend to mat when wet and can suffocate the plant.)
Changing Hydrangea Color
Color of the hydrangea flower is influenced by the acidity of the soil
Hydrangeas may produce pink, blue, or lavender blooms, depending on where it’s planted and how it’s fed. The presence of aluminum in the plant ultimately determines the color, and pH affects the uptake of aluminum. Alkaline soils, pH of 6.0 or more, are more likely to produce pink blooms, and more acidic soils, pH 4.5 to 5.5, produce blue flowers.
Pink hydrangeas can be turned blue by applying aluminum sulfate to lower the pH and add aluminum to the soil. Applying lime to raise the pH level will help blue hydrangeas turn pink. If your soil naturally produces very blue or very pink hydrangea flowers, you may need to grow your hydrangeas in containers or raised beds to achieve the desired color. If you do attempt to change the color of your blooms by adding these minerals, dilute them well, and add sparingly as it is very easy to scorch your plants by adding too much.
To go blue
To increase acidity (for deeper-blue flowers): Apply a solution of 1⁄4 ounce aluminum sulfate per gallon of water three times per year. (Aluminum sulfate is a colorless salt obtained by the action of sulfuric acid on hydrated aluminum oxide.) Soak the ground with the solution after the plant starts growing in the spring and repeat twice at 3- to 4-week intervals. Once a year, in the spring, apply 25-5-30 fertilizer, according to manufacturer’s instructions.
To go pink
To increase alkalinity (for changing blue flowers to pink): In the spring or fall, spread ground limestone (dolomitic lime) at a ratio of 4 pounds per 100 square feet and water it well. (Excessive alkalinity will cause chlorosis, or yellow leaves.) In the spring or fall, apply 25-10-10 fertilizer, according to the manufacturer’s instructions.
Other factors
» Hydrangea flowers will naturally fade and dry in the fall, often to a combination of pink and green or tan. This is simply the aging process, which cannot be reversed.
» Hard water (water with a high mineral content) can also affect the flower color, turning blue flowers more pinkish, so use rainwater to water your hydrangeas, when possible.
