The basic rule to tell if a hydrangea needs to be watered is by looking at the leaves. If the leaves are drooping, the plant more than likely needs to be watered.
If you've overwatered your hydrangeas, you can revive them by removing dead roots and replanting them. Afterward, be sure to check the soil to ensure you only water your plant when it's required. And keep an eye on the growing conditions to determine what it needs.
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.
Just like Hydrangeas getting too much sun, a Hydrangea getting too much sun may develop wilting and yellowing leaves, even some brown spots.
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.
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.
Symptoms of Phytophthora root rot are the sudden wilting and yellowing of the foliage. Infected hydrangea roots may exhibit brown discoloration and this discoloration can be seen on crown at the soil line and stem above the soil line as well.
Removing spent flowers will ensure your hydrangeas produce healthier, more bountiful blooms later on.
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.
Iron deficiency is common in hydrangeas and can cause the leaves to turn yellow. A sign that your hydrangea is suffering from an iron deficiency is if the new leaves are yellow while the veins remain green. This is called "chlorosis" and it's a sure sign that your plant needs more iron.
You might be able to revive less-wilted blooms in just an hour or two, so check on them a few times while they soak to see if they're back to looking their best. If you notice they still look wilted after a few hours, leave them to soak overnight to see if that does the trick.
Symptoms of overwatered hydrangeas may include brown and wilted leaves, yellow leaves that will drop from the plant, and stunted growth. Signs of root rot may present themselves as well. This could appear that half of your plant is dead, and you may see white fungus near the crown of the hydrangea.
Hydrangeas should be planted in moist, rich soil. In soil that drains quickly, such as sandy soil, wilting occurs much faster than in soil rich in organic matter with better water-holding ability. Shallow watering can also cause wilt.
Signs of root rot are slow growth, mushy stems, and wilting, yellow, distorted leaves (especially when the plant has been well watered, as wilting leaves can also be a sign of a dry plant). Usually the soil will smell rotten and the roots will appear to be reddish brown.
Root rot can be identified by the presence of soft, brown roots. The root system of a healthy plant should be firm and white. But when soil is soggy, fungal spores multiply and the fungus starts to spread3, developing in the extremities of the roots first.
Signs of Root Rot
Unhealthy roots appear dark brown, black, mushy, fall apart, or smell like decay. Other symptoms of root rot: A large number of yellowing or smaller, pale-colored leaves. A lot of leaves wilting or falling off the plant (unseasonably)
For hydrangeas planted in ground.
For optimal growth, bloom production, and quality, fertilize three times: In early spring when plants are just leafing out. In early May to boost their flower production for summer. In late June/early July to help your plants finish the summer strong.
Most common hydrangeas prefer a partial sun location - ideally receiving sun in the morning hours and shade in the afternoon. The reblooming Endless Summer® Hydrangea series prefers part shade.
Potted hydrangeas overwinter best in a garage or basement where the temperature stays cool but doesn't freeze. The plants will go dormant, but you'll still need to water the pots occasionally, about once a month, to keep the roots moist, until spring.
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.