Why are hydrangeas susceptible to heat stress? Hydrangeas are plants that love water, which made the heat particularly tough for them. When hot temperatures occur, plants need to cool themselves, just as we seek a cool place during the heat of the day. Unfortunately for plants, they can't get up and move!
To help protect your hydrangeas from drooping, plant them in a location that keeps them shielded from the afternoon sun. "Filtered sun, as beneath pines, is great," says Doggett. "Keep in mind that hydrangeas do need some sunlight in order to bloom well."
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.
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.
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.
Drooping Leaves
The most likely cause of this is a lack of water. You will typically see these leaves drooping in the afternoon, especially if your plants are receiving too much afternoon sun. Hydrangeas are at their best planted in partial shade with four to six hours of morning sunlight.
During really hot weather, water your vegetables at least two to three times a week. Watering the garden deeply is critical. The water must go down, down, down to encourage deep roots and get away from the hot soil surface.
Burnt leaves and fronds in the garden look awful and are a constant reminder of the hot weather we've been experiencing. Ugly as it is, the best thing to do about burnt growth is to leave it be and to provide as much water as possible to damaged plants.
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. Plus, panicle hydrangeas are the hardiest hydrangeas.
Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. The coffee grounds make the soil more acidic, allowing the hydrangea to more easily absorb aluminum. In addition, fruit peels, lawn clippings, peat moss and pine needles, are thought to have a similar effect.
It's best to start adding coffee grounds to the soil months before the blooming season begins, ideally in the late fall. You can repeat the process with your typical fertilizing schedule.
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.
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.
It can take anywhere from a couple of days to a couple of months for stressed plants to recover. Recovery time depends on the amount of damage that the heat caused to the plant. If a stressed plant is completely neglected during a heatwave, it can take several months or even be impossible to revive it.
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!
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.
Be Consistent
You should check the moisture level around the base of your plants. Determine the watering schedule you need to keep in order to maintain the right level of moisture. Watering every day or every two days doesn't matter nearly as much as consistent watering. Make a schedule and stick to it.
But don't overwater
Plants sometimes wilt from the severe sun, even when they have sufficient water. Test the soil before you water, Young said. If a pot feels heavy or the soil feels damp an inch or so under the ground, your plant probably doesn't need more moisture.
If you forget or are too busy to water your plants on some summer mornings, you can water them at night. However, this should not be your ordinary watering time. Morning is the proper time for watering plants, though you should keep in mind that not all plants need daily watering.
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.