Too much sun exposure can cause your hydrangea shrubs to burn on its leaves and blooms. Also, be sure to put your fingers in the soil to see if it needs watering. We do recommend a soak versus light watering each day, but you should be sure that the soil is always moist – not wet – by sticking your fingers in the dirt.
In warmer areas, many hydrangea types will suffer in the afternoon's scorching sun. The leaves and flower heads may burn, turning brown. If you notice this, that means your hydrangea is getting too much sun. Try moving it into filtered shade, or an area where it gets only a few hours of morning sun.
Most hydrangeas prefer only morning sun. Yet one type of hydrangea can soak up the sun all day: the panicle hydrangea. While they can stand the sun, these do just fine in partial shade, too.
Shade cloth is available at many garden centers and home improvement retailers. It comes in different densities so get the one that provides the most shade. This is a temporary covering. You set out wooden stakes around the plant(s) and then drape the shade cloth over the plant(s) using the stakes for support.
Many people think that you need a shady garden in order to grow hydrangeas. While that is true for some varieties, some hydrangeas thrive in sunny spots and even need full sun to develop into the fullest plants and the brightest blooms.
Bigleaf hydrangeas, also known as hydrangea macrophylla, vary especially with some of the newer cultivars being bred to better tolerate heat and sun, but most of these including the mopheads and lacecaps prefer some shade, especially during the afternoon.
Panicle hydrangeas can handle hot sun
While they are drought tolerant and stand up to heat, I still like to provide shade during the hottest part of the day. And just because they are drought tolerant doesn't mean you should let them wilt. As with all hydrangeas, plants will thrive with regular irrigation.
Provide Some Shade
Most varieties of hydrangea prefer shade during the heat of the day. Most varieties of hydrangea prefer afternoon shade. If you think your hydrangea can benefit from a break from the sun you can purchase shade cloth online or from your local garden center.
Hydrangea Heat Stress
Heat and drought stress can cause the stomata of your hydrangea plant to remain open as they try to absorb water vapor from the environment that they are in. Unfortunately, this causes water to be lost more than it is gained which over time translates into wilting.
Hydrangeas need more water than most garden plants and will begin to wilt quickly without it. To ensure that Hydrangeas thrive, water deeply two to three times a week in the summer. Be sure to water in the morning or evening so that water does not evaporate as quickly as it would during the heat of the day.
While several species of hydrangeas thrive in shade, panicle hydrangeas (Hydrangea paniculata) are the best for growing in full sun. These summer-blooming shrubs produce large clusters of white flowers for several weeks.
Typical symptoms include yellowing leaves, or irregular dry, brown blotches. Leaf tips and margins may turn brown, as well. Severely damaged leaves may drop from the plant. Leaf scorch results when the leaves lose water faster than it can be supplied by the roots, so wilting may occur before scorch is noticed.
Brown, tan, yellowish or black spots on hydrangea leaves may be anthracnose. You can also identify it by cankers that form on stems and branches. Anthracnose can be fatal to hydrangeas, so prune out dead or diseased plant parts and destroy them.
Water at a rate of 1 inch per week throughout the growing season. Deeply water 3 times a week to encourage root growth. Bigleaf and smooth hydrangeas require more water, but all varieties benefit from consistent moisture.
Here's what to look for: Leaf discoloration: hydrangea laves typically become yellow and brown when overwatered. However, the discoloration can also be a sign of underwatering. Usually, when the plant is overwatered, the browning occurs on the edges of the leaves.
But hydrangeas are among the few plants that can draw moisture in through their florets, so it's possible to perk up wilted blooms by completely submerging them in water and letting them sit for a few hours to rehydrate.
Removing spent flowers will ensure your hydrangeas produce healthier, more bountiful blooms later on.
Apply mulch, preferably a reflective mulch such as dry grass clippings. The first line of defense against hot weather and the windy conditions that can dry surface soil is to apply a liberal layer of mulch around the plants. This protects the soil from direct sun exposure, keeping it moist at the surface.
Water them for longer.
If you notice that your hydrangeas are starting to look stressed, de Corral says to try and shift your watering schedule to less frequent one, but with longer intervals.
Water your hydrangeas in the morning before the heat of the sun is strong enough to quickly evaporate soil moisture. Try to avoid watering at night, which can encourage mold and mildew as the moisture sits through the cool night. Water your hydrangeas through the growing season as well as in late fall.
Put on a kettle of water and bring it to a boil. Pour the boiled water into a container. Remove the wilted hydrangeas from your arrangement and re-cut the stems on a 45-degree angle. Make a vertical slit in the incision and hold the stem upright in the boiling water for about 60 seconds.
Hydrangeas are susceptible to sunburn because they are a shade plant. Their leaves are sensitive to desiccation from heat and sunlight, and it's common for the foliage to turn yellow or brown in bright sunshine.
Hydrangeas need regular water to thrive. Too little water can result in stunted growth and failure to develop flower buds. A drought in the previous growing season can also affect flowering the following year. Plants need consistent moisture, about 2 inches of water per week.
Both over and under-watering your hydrangeas can cause them to weaken and brown, so Myers says it's crucial be precise about irrigation. "Water established plants thoroughly but less frequently to encourage deep roots that are more drought tolerant," she says.