August 1, 2022 Caring for Hydrangea

August 1, 2022

Caring for Hydrangea

“A dead hydrangea is as intricate and lovely as one in bloom.”

―Toni Morrison

This past weekend was the Sauk County Master Gardeners Association (SCMGA) Annual Garden Tour and it was a blast! We had visitors from all over Sauk County plus from neighboring counties. We even had visitors from nearby states. The attendees had the opportunity to “peek” into gardens that they would not normally have a chance to visit. The added bonus was the SCMGA docents who were onsite at each location, eager to answer any questions visitors had. Questions ranged from “What is that plant?” to “where did you get your plant markers?” to “how do I get my hydrangea to bloom?” For most questions, the docents had answers but there were a few that stumped even the most seasoned master gardener. For me, the question about why hydrangeas were not blooming is an issue I struggle with as well.

Hydrangea come in a variety of forms, colors, and sizes. They can be planted in grouping, as shrub borders, or in containers. Their flower heads can provide interest not only during the blooming season, but also into the winter. My grandmother had border of white hydrangea on the north side of her house. This type bloomed on new wood that started out white and gradually turned pink. I added an ‘Incrediball’ smooth hydrangea to my landscape as it reminds of her hydrangeas.  The blooms can get as big as your head however, mine does not as it is planted in partial shade. Lack of sun is one of the reasons why hydrangeas won’t flower. The other most common reasons why hydrangeas won’t bloom include improper pruning, cold injury, too much nitrogen, and lack of water.

If your hydrangeas do not get enough sun, they will bloom poorly or not all. This is most likely the reason I have for some of my hydrangeas not blooming. I always thought heavier partial shade was better so I have several planted in spots where they could use more sun to bloom to their full potential. Most need 3 to 4 hours of direct sun each day, preferably in the morning with shade in the afternoon.

To avoid improper pruning, determine what kind of hydrangea you have. Some hydrangea bloom on new wood and others on old wood. Smooth and panicle hydrangea bloom on new wood. Some panicle varieties are ‘PeeGee’, ‘Pee Wee’ ‘Limelight’ and ‘Little Lime’. Examples of smooth or “snowball’ hydrangeas include ‘Grandiflora’ and ‘Annabelle’. These should be pruned late winter or early spring before any spring growth. Hydrangeas that bloom on old wood should be pruned right AFTER they bloom in the summer. Examples include lace-cap, oakleaf, climbing and big-leaf types.

Cold injury is another reason your hydrangeas might not bloom. Some hydrangeas are not as hardy as others, so your best bet is to plant varieties that are hardy where you live. Panicle and smooth hydrangeas are the most cold hardy. If you have one of the other varieties, consider protecting it in the winter.

If you have lush green shrubs with very little blooms, your soil may have too much nitrogen. If you’ve determined your soil is lacking nutrients, add a fertilizer that is high in phosphorus to encourage blooms.

Another common reason your hydrangeas may not bloom is lack of water. Hydrangeas are like consistently most, well-drained soil. If your hydrangea is wilting, it won’t bloom well. If need be, add a layer of mulch around the base to help retain moisture. Knowing what kind you have may require a bit of research, but it goes a long way to helping ensure you’ll be successful growing and getting them to bloom.

This week’s article is written by Jeannie Manis, a Wisconsin Certified Sauk County Master Gardener Volunteer. If you have any gardening questions, please contact the Extension Sauk County by emailing to  trripp@wisc.edu or calling the University of Wisconsin Madison Division of Extension Sauk County office at 608-355-3250.

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