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.
Removing spent flowers will ensure your hydrangeas produce healthier, more bountiful blooms later on.
"If you want a longer stem, you can make a deeper cut as long as it is done before July or August when the plant begins forming buds for next year's flowers." For smooth hydrangeas, she suggests removing the faded flowers as soon as they fade to green to ensure a second flush of smaller flowers in the fall.
Without going through the deadheading process, hydrangeas will not produce as many flowers and the few produced may not grow as big to their full potential.
To rejuvenate the hydrangea, remove up to 1/3 of the older living stems down to the ground each summer. This will revitalize the plant. If necessary to control the size of the plant, cut back before late July to allow for buds to develop. Usually the plant will return immediately to its former size.
Keep good air space between the plants; don't crowd them together or against other plants. Don't give bigleaf hydrangeas too much love; if they're too comfortable (water, fertilizer, etc.), they may devote all their foliage to leaves instead of blooms.
If it blooms blue, it's a hydrangea that should be pruned in late summer, as necessary. If it doesn't have blue flowers and it blooms later in the summer (after July 4), it's probably a good candidate for late-winter pruning.
Cut the dead stumps down to their base to completely remove them. This will allow the new growth underneath to have a chance to succeed. Dead and old blooms need to be removed to make room for new buds to come through. Cut the flower head off right above the first few leaves to encourage blooms for the next summer.
With insufficient watering, the leaves will begin to fade, and the flowers will turn brown. When hydrangeas do not get enough water they begin to get crispy; their leaves, their flowers… it's not pretty. It is very common to see them in a mid day slump.
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.
Hydrangea blossoms are at their best when they are well watered and well fed. Mulch also provides an evaporation barrier. Keeping your soil moist in the heat of the summer, which is also the flowering season for hydrangeas, will help to maintain the healthiest version of your plant.
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.
While some plants bloom on new growth, others primarily set flower buds on old wood. Regardless, it is best to wait to prune all hydrangeas until spring. In the fall, hydrangeas (and all trees and shrubs) are in the process of going dormant. They do not produce very much new growth until the following spring.
To get bigger flowers, cut them all the way back
In late winter or early spring, these shrubs can be cut all the way back to the ground. Smooth hydrangeas will produce much larger blooms if pruned hard like this each year, but many gardeners opt for smaller blooms on sturdier stems.
So these shrubs should be pruned immediately after their flowers fade. Conversely, if the shrub flowers on new wood (stems developed during the current season), its buds are set within the season, so the shrub should be pruned in early spring before that new growth emerges.
Mophead hydrangeas look lovely in the fall when their blue, purple and pink flowers contrast with the fall foliage. Brown flowers can be snipped off if they annoy you, but you don't have to remove them.