There is a hydrangea for every setting, with many compact varieties suitable for containers and smaller gardens, double-flowered choices and plants that offer a change in color as flower heads mature. Hydrangeas are relatively easy to care for.
Hydrangeas grow best in moist, well-draining soil with dappled shade. Too much sun and heat will delay or inhibit flowering.
1. Soil
Hydrangeas grow best in rich, well-draining soil. Add organic matter such as compost or aged manure at the time of planting, especially if your soil is sandy or heavy in clay. Mulching with a 2″ high water-retaining berm around the shrub’s base is also useful to keep soil moist and cool, reduce watering needs and improve soil texture. Hydrangeas need consistent moisture throughout the growing season but a good deep soak three times a week with a “doughnut” or soaker hose is better than frequent sprinklers as this encourages root growth and blooms rather than leafy growth.
When planted in garden soil, dig a hole larger than the plant’s container and backfill about halfway up to the top of the root ball with the soil mixture you prepared earlier (bonus points if you mix in some of Espoma’s Organic Soil Acidifier or Organic Garden Lime for blue flowers or rhododendron fertilizer for pink ones). Gently press soil down around the roots, tamping as you go to remove air pockets and help settle the soil. If the hydrangea is being planted in an open site consider mulching to prevent drying out from the summer sun or wind.
Some varieties such as the mophead and lacecap flowers need partial shade to avoid fading to green or brown but most are quite adaptable and will tolerate light to moderate shading in a sunny garden. If you live in an area susceptible to frost protect your plants by covering them with a burlap tarp over winter, removing it in spring once new buds have started to form. A fungus called powdery mildew may also be problematic; spray the leaves with a fungicide labeled for this disease at first signs of infection.
2. Water
Hydrangea plants are thirsty, so they require frequent waterings. When growing in the ground, hydrangeas like to be watered thoroughly to the point that the soil is soaked. This type of watering prevents disease. Hydrangeas also prefer cool conditions, and will wilt in hot weather if they are not well-watered. They can be revived by thorough watering and a bit of fertilizer, however.
Depending on the hydrangea variety, different amounts of sunlight and watering are needed. In general, reblooming varieties such as the Endless Summer, Blushing Bride and Twist-n-Shout need partial sun in the morning, but full shade during the afternoon. Other hydrangeas such as lacecaps and mopheads need a little more shade, but still not full sun.
When growing a hydrangea in a container, plant it in high-quality potting soil that contains slow-release fertilizer. Fill the pot so that the top of the hydrangea root ball is level with the rim of the container. Add a layer of organic mulch (wood chips or compost) around the hydrangea to keep the soil cool and moist, and to add nutrients over time.
If you are trying to change the color of your hydrangea blooms, adjust the pH of your soil. The lower the pH, the more blue your hydrangea flowers will be; the higher the pH, the pinker they will be. You can test the pH of your soil using a simple pH tester that you can purchase online or at most garden centers.
Hydrangea plants do not need to be fertilized very often, but they should be fed when the soil is dry to the touch. Use a slow-release fertilizer that is recommended for hydrangeas in your climate, such as a 10-10-10 or 12-4-8 granular. Don’t feed hydrangeas after July or August, as this will encourage tender growth at the very time when they should be going dormant for winter.
3. Pruning
Hydrangea plants are renowned for their flowers and foliage, but many gardeners don’t know when to prune them for maximum blooms. Pruning at the wrong time of year can reduce flower production or even cause the shrub to die.
The type of hydrangea you have and how it is pruned dictates when you should trim the plant. Some species, like the popular ‘Endless Summer’ and ‘Pee Gee’ hydrangeas, form their flower buds on old wood and should be pruned in late winter or early spring. This type of pruning allows the plants to grow into more multi-stemmed small trees, but requires regular annual trimming to keep them in shape. Other varieties, including ‘Annabelle’ and ‘Grayswood’ hydrangeas, produce their flower buds on new growth and should be pruned right after they finish blooming in summer or autumn. This prevents the next year’s flower buds from being harmed over winter.
Bigleaf hydrangeas form their flowers in a structure called a panicle that is essentially a cone shaped head from which the petals emerge. These flowers are usually white but can vary in color, depending on the cultivar. Each panicle contains sterile florets that are the larger, showy flowers and fertile florets that appear inside the ‘cone’, closer to the central stem.
Some hydrangeas, such as ‘Preziosa’ and ‘Grayswood’, are hybrids that are considered reblooming. They set their flower buds on both old and new growth, making them a good choice for cold climates where the older stems are more likely to be harmed over winter. Like reblooming types, they are best pruned after flowering and only to remove dead or damaged branches. Always use a sharp pair of pruning shears to create clean cuts and minimize disease.
4. Fertilization
Hydrangeas do not require regular fertilization, but they will benefit from a well-balanced fertilizer applied at least once a year. A balanced fertilizer that contains nitrogen (N), phosphorus (P) and potassium (K) should be used; one with higher levels of P will encourage larger blooms. Organic or inorganic fertilizers are both suitable, but if an inorganic fertilizer is used, it should be a controlled release type like Osmocote or other slow-release options that last the entire growing season and feed the plant slowly over time.
The pH of the soil is important for hydrangea flowers because it determines what color they will be. A soil test is available from most garden centers and will tell you what your soil chemistry is. A hydrangea planted in acidic soil (pH 5.5) will produce blue flowers; plants in neutral or alkaline soil will usually produce pink flowers. To change the color of your hydrangea flowers, you can raise or lower the pH by amending the soil with products that contain sulfur or aluminum, but this is best done after two years when the plant is established.
Newly planted hydrangeas need to be fed with a high nitrogen fertilizer to assist them in establishing roots and growing shoots, but the nitrogen level should drop once the plant is established. For the most beautiful hydrangeas, apply a low nitrogen fertilizer at the start of the growing season and again just before the blooming period. This will help the plant to transfer energy throughout the plant that is needed for developing large and vibrant flowers. If your hydrangeas are struggling to bloom, the plant may be deficient in phosphorus or potassium.
5. Temperature
A hydrangea plant that isn’t getting enough sunlight or that doesn’t have the right temperature could be suffering from stress, which can lead to wilting and other issues. You can help your hydrangea thrive by tracking the daytime and nighttime temperatures in your area and making sure that they are within an ideal range for your plants.
While hydrangeas can take full sun, they prefer partial shade during the afternoon, especially for mophead and lacecap varieties such as Endless Summer, BloomStruck, Blushing Bride and Twist-n-Shout. This shade keeps the soil from drying out, which helps the hydrangea to produce large and healthy flowers.
Hydrangeas are also very sensitive to sudden changes in temperature, which can result in misshapen blooms. It is helpful to track the average frost dates in your growing zone and plan to plant hydrangeas in early spring or fall so that they have time to settle in before extreme temperatures arrive.
Another way to keep your hydrangeas happy is by mulching around their roots. This helps protect them from the cold and reflects heat back onto the soil to help it retain moisture, which is important for hydrangeas in warm climates.
If you live in a cooler climate, the best time to plant your hydrangeas is fall because it gives them a chance to get settled before winter arrives. It’s also easier to transplant hydrangeas in fall than it is in the spring because they are more dormant at that time. It is also a great time to add organic matter such as rotted manure, homegrown compost, leaf mold or pine bark fines (fine-textured mulch) into the planting site. These ingredients create rich and loose soil that can better hold water so the hydrangea doesn’t become overly dry.
