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.
If your hydrangea foliage is also damaged, it may be sunburned (crispy or brown around edges). Depending on the amount of total damage, your plant will eventually recover from severe sunburn, but may not rebound from extreme drought.
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.
Can hydrangeas grow in full sun? Hydrangeas like morning sun, but do not do well if they're in direct, hot afternoon sun. Partial shade in the later parts of the day is ideal for these beauties.
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.
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.
TOO MUCH SUN
Conversely, too much direct sun may stress hydrangea plants, which can force them to conserve energy by not forming flowers.
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.
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.
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.
After a good watering, your hydrangeas will likely get some regrowth, although for severely damaged plants it may be next summer before they regain their former glory. Avoid pruning; the resulting lush new growth will be sensitive to further damage from heat waves later in the summer.
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.
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.
Unfortunately, there's no aloe vera to put on your plant's sunburn, and it won't eventually fade into a tan. “If you find your plant has been burnt, it is best to cut off the damaged leaves or trim them if you can,” says Steinkopf. “They will not heal or turn green again.”
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.
Place the hydrangeas on the cutting board and use the sharp knife to cut the end of the hydrangea at a 45 degree angle. Then cut a small slit vertically up the middle of the newly trimmed stem. Place the hydrangea(s) in the vase filled with hot water. Let sit for a minimum of one hour and voila!
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. Place the hydrangeas back in your floral arrangement and they should revive themselves in an hour or so.
There's no way around it: Hydrangeas in pots will have to be watered more frequently than those in the ground. Because it's living in a smaller space, you can expect this space to dry out more quickly than the ground will. To keep your potted hydrangea happy, try watering it every other day in the summertime.
The common reasons for a dying hydrangea include; the wrong choice of the potting soil, exposure to direct sun, poor watering habits, and, exposure to too much wind.
"Warm temperatures and humid conditions can cause the stems of your hydrangeas to weaken and the blooms to flop over," explains gardening expert Melinda Myers. "Much like weeds, plants can overgrow when exposed to too much moisture."
If you don't prune hydrangeas then they can eventually resemble a tangled mass of woody stems, and the flowers will become smaller and less showy.
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.
The combination of too much sun and not enough water is a common cause of hydrangea droop, making it a great place to start when your plants are feeling unwell. Check the moisture level of your hydrangea at a point 1 to 2 inches (2.5-5 cm.) below the surface of the soil with your finger.
Removing spent flowers will ensure your hydrangeas produce healthier, more bountiful blooms later on.