Q: I have hydrangea plants that I planted four years ago. They are in a fairly shaded area. They get excellent leaf growth every year but not one bloom. What am I doing wrong?
Jim Hansen, Sacramento
A: Most likely, their lack of flowers comes down to pruning, either at the wrong time or the wrong branches. But these issues can be rectified with a little patience.
Your best solution: Do nothing. Give your hydrangeas a year off from pruning. Then, remember some basic rules when pruning after next spring’s bloom.
Never miss a local story.
There are many types of hydrangeas, say UC master gardeners, and the timing of the pruning depends upon whether the hydrangea blooms on current or previous years’ growth.
The mophead varieties (Hydrangea macrophylla) are the most common and have large, globe-shaped flower clusters. Judging by reader letters, these also are the ones that tend to offer the most challenges. These shrubs bloom on previous years’ growth or “old wood.” Pruning in late fall or early winter will eliminate the bloom for next spring.
But they won’t bloom again on a branch that has already bloomed. So, the solution is to prune in late summer when the flowers start to fade.
Branches that bore flowers should be cut to within a foot of the ground or cut back so that only two to four buds remain on the branch. This is done in the hope that some of these buds will grow into branches before the plant goes dormant. And since these kinds of hydrangeas flower on wood that grew in the previous year, there is potential for more flowers next spring.
Many gardeners prune hydrangeas a second time in January because, while the plants are out of leaf, it is easier to identify and eliminate crossing branches and old wood. Removing old wood makes more room for new branches to sprout from the crown of the plant.
The important point to remember is that they bloom on the growth that grew the prior season but didn’t flower.
Otherwise, hydrangeas need little pruning except to deadhead or to remove dead stems. To encourage a particular shape or size, prune right after your bush blooms.
Older hydrangeas may benefit from some rejuvenation pruning. This involves removing about one-third of the older stems down to the ground to allow light to penetrate to the center of the shrub and to encourage replacement limbs. (This also improves air flow through the plant and helps prevent fungal diseases.) This pruning can be done in the summer or in the winter, at the expense of some blooms. Pruning by a third will eliminate some flowers the next spring and should not be done every year.
Fertilizing usually is not necessary, but the plants will respond to an application of a slow-release, balanced fertilizer during the spring growing season. Apply per label instructions. With your plant, you may want to give it a little bone meal to prompt blooms, too.
Mulching is a good practice as it helps hold in moisture around the roots and the decaying organic matter adds nutrients to the soil. Those nutrients will also benefit blooms.
You may have no blooms this year, but your bushes likely are primed to have a lot of flowers next spring. Just give them a year off from pruning and see what they do.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:
Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. Monday-Thursday
Amador: (209) 223-6838; 10 a.m.-noon Monday-Thursday; email ceamador. ucdavis.edu
Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays
Colusa: (530) 458-0570; 9 a.m.-noon and 1-4 p.m. Tuesdays; website: cecolusa.ucanr.edu
El Dorado: (530) 621-5512; 9 a.m.-noon Tuesday-Friday
Placer: (530) 889-7388; 9 a.m.-noon Tuesday-Thursday or leave a message and calls will be returned; website: pcmg.ucanr.org/got_questions
Nevada: (530) 273-0919; 9 a.m.-noon Tuesday-Thursday or leave a message
Shasta, Tehama, Trinity: (530) 225-4605
Solano: (707) 784-1322; leave a message and calls will be returned
Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Monday-Tuesday and 1-4 p.m. Thursdays
Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned