When to Prune Oakleaf Hydrangea Exactly?

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1. What is Oakleaf Hydrangea?

Oakleaf hydrangea (hydrangea quercifolia) is a variety of hydrangea originating in the United States. Its leaves are so similar to the leaves of oak trees, so people call it the oakleaf hydrangea.

Botanical Name	Hydrangea quercifolia
Plant Type	Shrub
Mature Size	8 ft. tall, 6-8 ft. wide
Sun Exposure	Full sun, partial shade
Soil Type	Moist, well-drained
Soil pH	Acidic
Bloom Time	Late spring, Summer
Flower Color	White, pink
Hardiness Zones	5-9 (USDA)

Oakleaf hydrangea likes well-drained and moist soil. At the same time, if the soil is rich in organic matter, it is the best choice for planting oakleaf hydrangea. The oakleaf hydrangea can grow up to 8 feet tall and wide in fertile, draining soil.

The more light the oakleaf hydrangea gets, the more lush it grows and the more beautiful its flowers will be. The oakleaf hydrangea typically grows during late summer and blooms between June and July next year. The flowers grow on the old wood.

If I want my oakleaf hydrangea to grow stronger and bloom more flowers in the coming year, the timing of pruning is the key.

The oakleaf hydrangea has two features:

Flower shape.

Leaves color.

The oakleaf hydrangea blooms cone-shaped small white flower clusters during its blooming period, small at the top and big at the bottom. Unlike the well-known bigleaf hydrangea (hydrangea macrophylla), its white blooms do not grow upward but fall to both sides or hang down.

Oakleaf hydrangea (H.quercifolia) ‘Back Porch’

Another feature of the oakleaf hydrangea is its leaf color. Fall foliage color changes from green to red.

2. When to Prune Oakleaf Hydrangeas?

Since oakleaf hydrangeas bloom on old wood, they can only be pruned at specific times rather than whenever we want to.

The oakleaf hydrangeas' flowers gradually start showing up in May. They go through the blooming period between June and July. From mid-August to April of the following year, the buds of oakleaf hydrangea are in the stage of formation and growth.

Therefore, I will prune it from June to July; the latest pruning time is early August.

3. Pruning Skills

Two parts hinder the growth of oakleaf hydrangea.

Withered flowers

Dead stems, weak stems, and inward-growing stems.

When I prune the oakleaf hydrangea, I will remove these two parts that hinder its growth.

The oakleaf hydrangea has a unique feature where the two bud points close to the cut will sprout new stems. But without enough apical dominance, the lower buds on the plant fail to thrive.

Therefore, when pruning, I first check if buds are present at the pruning point, then consider the stems' height and buds' direction. The oakleaf hydrangea is an opposite branch plant. So, the plant's shape determines whether the bud I retain is left and right or inside and outside.

The oakleaf hydrangea can grow so large. So, I will start hard pruning the large oakleaf hydrangea in June or July. Generally, I will prune the plant to about 6 inches (15cm) tall. I did this to keep the oakleaf hydrangea small, but it would not affect its blooming in the second year.

The prune method of oversized oakleaf hydrangea

4. Common Mistakes to Avoid

Pruning at the wrong time

The wrong pruning time will cause the oakleaf hydrangea to bloom less or even not bloom in the next year.

First, I don't overly prune the young oakleaf hydrangea, except for removing dead stems. When it is mature, I will prune it once a year.

Generally, I trim the oakleaf hydrangea in early August, that is, early summer. The latest pruning time is the end of August. At other times, I will not prune the oakleaf hydrangea.

Pruning at the wrong position

Cutting off the stems that did not bloom this year was wrong.

These oakleaf hydrangeas grow many flower buds in late summer. I will keep these flowerless stems and allow them to keep growing. These stems without flowers are more likely to sprout and bloom than those with flowers.

So, I will only prune the stems that bloomed.

Shabby scissors

Pruning plants with blunt scissors can seriously damage many cells of stems and infect cut wounds, which can slow the wound's healing speed and even lead to the death of plants.

A pair of scissors sharp enough to cut off the stem neatly. Before pruning, I use 70% alcohol to disinfect the scissors to prevent the spread of the disease.

5. Additional Tips and Care

Fertilizer

Oak leaf hydrangea is an easy variety to take care of. It hardly needs special fertilizer. I usually use some N-P-K balanced slow-release fertilizers in early spring.

If you want your plants' flowers larger and more, you can use potassium dihydrogen phosphate (KDP) diluted 800-1000 times for foliar spraying.

Watering

Keep the soil moist, but don't let waterlogged in the soil.

When planting your hydrangeas in pots, insert your whole index finger into the soil to check its moisture level. If you feel dry, you need to water the plant.

6. Conclusion

Day in and day out, the oak leaf hydrangea will show amazing colors in the garden or the pots. Among them, my two favorite varieties are snowflakes and ruby slippers. The ruby slipper blooms many deep pink flowers every time it enters the flowering stage. The best pruning time for oakleaf hydrangea is from June to early. Oakleaf hydrangea blooms on old wood, so remember not to over-trim, especially not to cut off stems that have not bloomed. Cutting off the withered flowers and stems is just right.

Bibliography:
Apical Dominance and Shoot Branching. Divergent Opinions or Divergent Mechanisms? Dun EA, Ferguson BJ, Beveridge CA. Plant Physiol. 2006 Nov;142(3):812-9. doi: 10.1104/pp.106.086868. PMID: 17093134; PMCID: PMC1630731.
A Growing Stem Inhibits Bud Outgrowth – The Overlooked Theory of Apical Dominance, Kebrom TH (2017), Front. Plant Sci. 8:1874. doi: 10.3389/fpls.2017.01874
Foraging in Plants: the Role of Morphological Plasticity in Resource Acquisition, M.J. Hutchings, H. de Kroon, Editor(s): M. Begon, A.H. Fitter, Advances in Ecological Research, Academic Press, Volume 25, 1994, Pages 159-238, ISSN 0065-2504, ISBN 9780120139255, https://doi.org/10.1016/S0065-2504(08)60215-9.
Comparing substrate moisture-based daily water use and on-demand irrigation regimes for oakleaf hydrangea grown in two container sizes, Ethan Hagen, Susmitha Nambuthiri, Amy Fulcher, Robert Geneve, Volume 179, 2014, Pages 132-139, ISSN 0304-4238, https://doi.org/10.1016/j.scienta.2014.09.008.
Theoretical models for branch formation in plants, Nakamasu, A., & Higaki, T. (2019). Journal of plant research, 132(3), 325–333. https://doi.org/10.1007/s10265-019-01107-9
‘Ruby Slippers’ and ‘Munchkin’ Oakleaf Hydrangeas, Reed, S. M. (2010). HortScience horts, 45(12), 1908-1909. Retrieved Feb 7, 2024, from https://doi.org/10.21273/HORTSCI.45.12.1908
Oakleaf Hydrangea ( Hydrangeaquercifolia Bartr.) Horticulture, Genetics, Breeding, and Conservation, Andrew Sherwood, Matthew D. Clark, Stan C. Hokanson, Book Editor(s): Ian Warrington, First published: 04 November 2021 https://doi.org/10.1002/9781119851981.ch1

My name is Arthur Mo. I am a gardener who loves gardening so much. I graduated from Ocean University of China. After I returned to Japan, I began to learn how to cultivate hydrangeas and daisies. Mr. Mitsuhiro (my master) taught me to sow, cut, fertilize, and manage diseases and pests. For nine years, I have been sharpening my planting skills. In 2022, my family and I moved to Florida. The warm climate of Florida gives me the impulse to continue cultivating hydrangeas and daisies. I began my gardening trip in my backyard and unswervingly contributed my efforts to these plants. I love these plants deeply, and at the same time, I also thank my family, my master, and friends for their understanding and support.