The primary reasons hydrangeas don't bloom are incorrect pruning, bud damage due to winter and/or early spring weather, location and too much fertilizer. Hydrangea varieties can be of the type that blooms on old wood, new wood or both. Old wood is the current year's growth and new wood is next year's (spring) growth.
There are plenty of reasons why your hydrangeas may not be blooming as much as they once did. Conditions like extreme heat, drought, or excessive sun exposure can all impact how many flowers your shrubs produce. Pruning is also an important consideration.
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.
Leaf Spots (Cercospora species and Phyllosticta hydrangea)
Watering without getting the leaves wet will help to prevent these diseases. If your hydrangeas do get infected, you have several options, including compost tea, hydrogen peroxide, garlic oil, or liquid kelp.
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.
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.
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.
Miracle-Gro Performance Organics Blooms Nutrition
This is an all-purpose blossom booster that's suitable for use on a wide variety of perennial and annual blooming plants, including 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.
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.
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.
The reason for hydrangeas wilting and dying is because there is not enough moisture around the roots due to lack of watering or rainfall, the soil drains too quickly, too much sun or excessive wind saps moisture from the leaves. Hydrangea flowers can droop due to excess fertilizer.
Shallow or inconsistent watering.
If a hydrangea is being watered every other day for twenty or thirty minutes (sadly, standard automatic irrigation settings) the plant is likely to wilt in hot weather. Once the flowers wilt a few times they will turn brown.
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.
Hydrangea Care Tips
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.
However, stop deadheading hydrangea shrubs in mid to late fall, leaving any spent blooms in place. This not only provides winter interest, but also ensures you don't remove the buds that will become flowers next spring.
How long it will take for your hydrangeas to perk up again depends on how far gone they are. 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.
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.
Yellow or Brown Leaves
When a hydrangea has been overwatered, one of the most obvious signs is yellow or brown mushy leaves. Touch your hydrangea's leaves just to make sure – dry leaves can be a sign of underwatering, so feeling them will help you tell the difference.
If the soil is wet, it's overwatered - if it's dry, it's underwatered. Browning edges: Another symptom that can go both ways. Determine which by feeling the leaf showing browning: if it feels crispy and light, it is underwatered. If it feels soft and limp, it is overwatered.
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.