How To Grow Hydrangeas From Start To Finish
Whether you trick them into pink or blue flowers, learning how to grow hydrangeas provides a fantastic floral display. We share our top tips!
Many novice gardeners may feel intimidated by the showy hydrangea. Thankfully, we are here to help you learn how to grow hydrangeas and to help you become confident in your ability to care for these lovely heirloom flowers!
There are many varieties available that range in size and flower color. You can even cultivate pink or purple flowers depending on the soil pH, and they all have unique requirements.
Most people don’t realize that hydrangeas have been around for millions of years in the wilds of Japan and Indonesia. Some hydrangea fossils are dated at almost 60 million years old! The Japanese were the first to cultivate the hydrangea, with the plant being mentioned in poems dating from 710 A.D.
It is said that the hydrangea flowers represent love, understanding, and gratitude, which can motivate many to plant hydrangeas in their garden. Let’s dive into this in-depth guide to learn all about growing hydrangeas in your own garden!
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Quick Care Guide
|Common Name||Hydrangea, Hortensia|
|Scientific Name||Hydrangea spp.|
|Height & Spread||Up to 15 feet tall and 6-10 feet wide|
|Light||Partial sun to shade|
|Soil||Well-drained and moist soil|
|Water||Deep watering during hot weather|
|Pests & Diseases||Aphids, Japanese beetles, spider mites, root rot, powdery mildew, bacterial leaf spot|
All About Hydrangeas
There are approximately 70 species of hydrangeas in Asia and it wasn’t until the 1700s that they planted hydrangeas in England. The hydrangea botanical name is Hydrangea spp., simply known as hydrangeas or hortensia. Each species will have a common name, such as French hydrangeas and Oakleaf hydrangeas.
Hydrangeas are deciduous perennials when not exposed to extreme temperatures. In the Mediterranean, hydrangeas are evergreen. Hydrangeas are dicotyledons with simple leaves that have jagged edges and net-like veins. Attributes vary depending on the species of hydrangea, but the flowers are the centerpieces of hydrangea plants.
The cluster of flowers ranges in color from white and lime green to pink and blue. Each star-shaped flower has four to five petals. Blooming flowers produce a sweet scent that is pleasing and unmistakable. Hydrangeas are great as ornamentals and a way to attract pollinators such as bees and butterflies to the garden.
The most common hydrangeas are shrubs, but there are climbing varieties and trees so you can find one that fits into your landscape. Mature size varies among species, but some can grow up to 15 feet tall and 10 feet wide. You can also find a variety that thrives in containers to add beauty to your outdoor space.
Types of Hydrangeas
Even though there are many species and varieties of hydrangeas, let’s narrow it down to some of the most popular choices of hydrangea. H. arborescens, H. paniculata, H. quercifolia, H. macrophylla, and H. serrata are the five we will highlight in this section.
H. arborescens ‘Smooth Hydrangea’
The smooth hydrangea is native to the eastern United States and displays a white flower color that has a bloom time from early summer to fall. The stem bark is textured and peeling and it is usually wider in width than height, reaching three to five feet tall. Compared to its cousin, the hydrangea macrophylla, the leaves are thinner and rougher. It prefers partial shade and plenty of moisture.
H. paniculata ‘Panicle Hydrangea’
Also known as peegee hydrangeas, they are one of the easiest to grow because they love the sun and are cold-hardy. H. paniculata flower color ranges from lime green and from white to pink with oblong clusters. Panicle hydrangeas have a bloom time in early summer and it grows up to six feet tall. They are hardy, and can be fairly low-maintenance when mature.
H. quercifolia ‘Oakleaf Hydrangea’
The Oakleaf hydrangea is another native of the eastern United States. It gets its name from the oak leaf shape of its leaves, which turn purple or red in the fall. The immature flower is white and turns purple with age. These plants need a sheltered location in the garden for the winter months to keep them from dying. Optimal conditions will ensure it grows to 4-6 feet tall with healthy flowers and a bloom time in early summer.
H. macrophylla ‘Bigleaf Hydrangea
Of the many types of hydrangeas, this is one of the most popular because of the hydrangea flowers produced. A common variety is Endless Summer because the bloom time carries over into early fall. The large mophead flowers have a vast range of flower color to choose from. To make it a blue hydrangea, you need to have acidic soil. More vulnerable to cold than other varieties, with a love for shade to partial sun, it will grow three to six feet tall.
H. serrata ‘Mountain Hydrangea’
Similar to the Bigleaf hydrangea and requiring the same hydrangea care, it has smaller leaves and flowers. It will reach heights from 2-4 feet tall. The flower color can be blue or pink with a bloom time in mid-summer. To get a blue hydrangea, plant in acidic soil, and for the pink hydrangea flowers, plant in alkaline soil.
Once you learn the basics, it isn’t difficult to care for hydrangeas. You will find growing hydrangeas is fun and worthwhile. This next section details what to do once you plant hydrangeas in your garden.
Light & Temperature
Plant hydrangeas in partial shade in a sheltered location. Typically, where they can receive warmth from the morning sun and protection from the full sun in the afternoon shade. They can tolerate full sun if it isn’t too hot; some varieties are more tolerant of heat. USDA growing zones 5-7 are best suited for these ornamental plants.
They grow the best at temperatures ranging from 50-60 degrees Fahrenheit. If you aren’t growing a winter hardy variety, you will want to protect your plants from the cold. Do this by covering the roots with a thick layer of mulch and planting them in a sheltered location. To protect from harsh winds, cover them with a wire cage wrapped with a burlap sack or plastic bag.
Water & Humidity
Hydrangeas prefer consistent moisture and will need to be watered at least three times per week until the roots are established. Once established, water at a rate of 1 inch per week to keep the soil moist. Watering the base of the plant in the morning will prevent the leaves from wilting in the hot sun and discourage the growth of fungus. Soaker hoses or drip irrigation can help with watering.
Over-watering can cause root rot, stunted growth, and yellowing of the leaves. They can tolerate humid climates if protected from the scorching sun. To prepare your hydrangea for the winter, water it deeply before it freezes. If the ground doesn’t freeze, water deeply and enough to prevent them from drying out.
Fertile soil that is alkaline or acidic is ideal for optimum hydrangea care. If you have a clay soil type or sandy soil type, remove some of the soil and add plenty of compost so water can drain adequately through the soil to prevent root rot while still holding enough to keep the plant happy. Otherwise, your plants will thrive with soil that has plenty of organic matter.
There is no specific soil pH required to grow these plants. However, if you have a bigleaf hydrangea (H. macrophylla), it’s possible to change the flower color by adjusting the pH of your soil.
Acidic soil lower than 6.5 will turn the flowers blue, while neutral to alkaline soil, will produce pink flowers. Add lime to make alkaline soil, or aluminum sulfate to achieve the blue hydrangeas. Don’t fall for garden myths, like adding baking soda to the plant’s soil. Stick with scientifically proven methods to change the flower colors if you choose to attempt it.
For the healthiest plant, fertilize your hydrangea regularly. During the growing season, use an all-purpose compost once per month. Then in the winter months, add a slow-release fertilizer in the late winter or early spring, so as it wakes up it will have food to grow and use for forming flower buds and at bloom time.
Repot your hydrangeas in the early spring before it comes out of dormancy. Inspect the root ball for any rot and gently realign any roots that encircle the root ball. Use an organic potting mix in your new pot that allows good drainage to prevent water damage to the roots.
There are a few ways to propagate hydrangeas with one choice not better than the other. Let’s look at a few so you can decide which method is right for you.
When growing from seed, you can either direct sow once the danger of frost has passed or you can begin the seed indoors 6-8 weeks before you plant them outside. Keep in mind, it can take up to two seasons for your new hydrangea to bloom. Also, some hydrangeas will self-sow, but this isn’t an effective method to ensure more hydrangeas.
Another option is to divide an existing hydrangea plant. Do this in the fall just before your plant goes dormant. Divide a plant that has at least two stems and then separate the stem from the root using a shovel. Fertilize and deeply water your separated plant.
The most popular method of propagation is to take a cutting from one or more of your hydrangea shrubs. Pick a new growth branch without a bloom and make sure there are three to four leaf pairs on the branch. Remove one leaf pair and dust rooting hormone on the leaf node. Next, put the branch in moistened potting soil and place it in a warm area with indirect sunlight.
It is easy to prune hydrangeas, and the technique depends on the variety of hydrangea you are growing. Pruning hydrangeas will help control the mature size and prepare them for the next growing season.
The Bigleaf hydrangeas (H. macrophylla), Oakleaf, and Mountain (H. serrata) should be pruned after the flowers fade in late summer because the flowers bloom on old growth, otherwise known as old wood. You can more readily see which is the old wood and which is newer growth this way. Pruning of these varieties is only meant to remove dead or diseased wood. Don’t prune in the fall, winter, or spring to prevent accidentally removing flower buds.
Flowers that bloom on new growth (a.k.a. new wood), such as the smooth hydrangea (H. arborescens) and panicle hydrangeas (H. paniculata), are pruned in late winter before new growth begins. Prune these varieties all the way to the ground if you want larger blooms the next season. For sturdier stems with smaller blooms, cut the stems to a height of 18 to 24 inches tall.
Deadhead spent blooms anytime during the growing season, being careful not to snip off new buds. Finish dead-heading by late summer because the old flowers left on through the winter can protect new buds from wind and cold exposure.
Thankfully, hydrangeas don’t have a lot of pests and diseases, but there are a few worth mentioning that affect the health of this ornamental plant. Caring for hydrangeas involves learning about common problems.
The most common problem is not having any blooms on your hydrangea. Pruning new wood instead of old wood (which removes flower buds), inadequate winter protection, and poor sunlight and nutrients are common factors to be considered if your plant won’t flower.
Aphids are small green (sometimes black) insects that are more likely to affect new growth because it is easier for them to pierce the stem and leaves to retrieve the sap. They excrete a substance called honeydew that attracts ants and if the aphids continue feeding on your hydrangea, it will cause the leaves to curl and wilt. The best way to get rid of aphids is to blast them with water. If that doesn’t work, neem oil or insecticidal soap are effective treatments. For extremely heavy infestations, consider a pyrethrin spray.
Japanese beetles arrive in the middle of the summer and can wreak havoc on hydrangea plants in a matter of days. They are commonly found feeding on the Oakleaf hydrangeas. Fortunately, they don’t kill the plant, but it will look unsightly when they are finished. Japanese beetles are easy to spot because they are metallic green and have brownish/copper wings with small white tufts under the wing covers. Handpick the beetles and place them in a bucket of soapy water or spray them with neem oil. Adding milky spore or beneficial nematodes to the soil can prevent their return.
Spider mites feed on the plant cells, causing yellow spots on the leaves and deformed stems. Since spider mites are minuscule in size, you will know they are there if you see webs on your hydrangeas. It’s best to try the least invasive method first, so spraying them off with water may do the trick. Ladybugs are a natural predator of the spider mite as well as aphids, so you can also purchase these beneficial insects or use other means to encourage them to your garden. Neem oil is effective on these as well.
Root rot is common in plants stressed by drought and affects the Oakleaf hydrangea (H. quercifolia) more than other varieties. This fungal infection will cause the leaves to turn yellow or brown, plant wilt, and/or browning of the root ball and stem. The best treatment is prevention. Do not overwater your hydrangeas and be sure to plant them in well-draining soil. If they are already infected, you may be able to use an organic copper fungicide if the disease isn’t advanced.
Powdery mildew is another fungal disease that can attack the hydrangea. It is seen more on the Bigleaf hydrangea (H. macrophylla). Signs include white powder on the leaves, or yellow and purple leaf blotches. If you catch it early enough, you can remove the affected leaves and make sure there is plenty of airflow between plants to prevent the spread. Otherwise, natural neem oil can be effective.
Bacterial leaf spot is caused by a bacterial infection that causes purple or red spots to form on the leaves. It is commonly seen on Smooth leaf hydrangeas (H. arborescens). It usually starts at the base of the plant and will work its way upwards. Remove affected leaves as soon as possible to prevent the spread of this infection. If the disease is severe, remove the affected hydrangea. Copper-based fungicides are sometimes recommended but aren’t 100% effective.
Frequently Asked Questions
Q: Where is the best place to plant a hydrangea?
A: The best place to plant a hydrangea bush is in a sheltered area where it receives full morning sun and shade during the hot afternoons of mid-summer.
Q: Do hydrangeas grow back every year?
A: Hydrangeas are perennials (meaning they grow back every year). However, if you plant a variety that is not cold hardy, it could die during the cold winter months. If your hydrangea does look worse for wear, there are steps you can take to revitalize them before writing them off altogether.
Q: How long does it take for a hydrangea to grow to full size?
A: Hydrangeas grow rapidly under optimal conditions. Knowing the average mature size of your specific hydrangea shrub will give you a starting point. Plant hydrangeas using the best-growing conditions as outlined in this guide and you could see your hydrangea grow as much as two feet per year until it is mature.