If your hydrangea blooms are turning brown too soon and quickly petering out, they likely need more water. Ditto if your flowers wilt during the day and don't bounce back at night. To confirm, look for brown spots on leaf edges. To fix, deeply water hydrangeas once a week.
If you object to their appearance as they turn brown, by all means clip them off. Some people cut them while they're still colorful and use them for bouquets indoors. Others snip them off and toss them in the compost, while some gardeners and homeowners prefer to let them drop naturally over the winter.
Removing a few crispy leaves or burnt mopheads is fine to improve your plant's appearance. However, resist the urge to prune severely and remove a large amount of the plant's foliage since that will cause further stress and a flush of tender new growth.
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.
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.
Prune back stems to just above a fat bud — called a heading cut — in fall, late winter or spring. These plants have conical-shaped flower heads. I recommend leaving the dry, tan flower heads on the plant to provide some winter interest in your landscape, so I wait to prune these until late winter or spring.
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.
4. No need to prune. If you trim your plants in fall or winter, you may mistakenly remove flower buds for the following year on bigleaf and oakleaf hydrangeas. Leaving the old flower heads on the plants will also add some interest to the winter landscape.
Place the hydrangea(s) in the vase filled with hot water. Let sit for a minimum of one hour and voila! Revived hydrangeas.
Hydrangeas that bloom on new wood can be safely pruned in late fall once the plants have gone dormant or in early spring. Next year's flower buds won't be formed until late spring the same year they bloom, so there is no risk of removing the buds if you prune in fall or spring.
The best time to deadhead is when the first set of blooms on your hydrangeas begin to turn brown and dry. Cut the stem below the flower head and just above the first set of leaves. For reblooming types, you can deadhead again when this second set begins to fade, but only through mid-August or so.
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.
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.
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.
Your hydrangeas might be beyond saving if they don't spring back after an overnight soak. It isn't recommended that you try to rehydrate them multiple times. They'll usually turn brown and disintegrate when submerged for a second go-around, so this hack only works once.
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.
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.
To reduce the size of a hydrangea that blooms on new wood, cut off about one-third of each stem in late fall or early spring before it begins to leaf out. If your hydrangea blooms on old wood, prune right after it has bloomed when the flowers are fading.