Companion Plants for Oakleaf Hydrangeas | Good and The bad

Have you recently added an Oakleaf hydrangea or two to your landscape? Excellent choice! You may now be wondering what you can pair it with to avoid resource competition.

Companion plants for Oakleaf hydrangeas (Hydrangea quercifolia) create a synergistic relationship through the sharing of vital resources and aesthetic cohesiveness.

What Is Companion Planting

This concept is generally defined as “growing specific plants together for their mutual benefit.” While this may sound simplistic, the remarkable list of benefits that comes from utilizing the natural relationship between plants is growing by the day.

In Southeast Asia, this symbiotic relationship was first observed by Chinese farmers over a thousand years ago. In Europe, the Greeks and Romans began documenting their use of companion planting in the second century, BCE.

In the West, however, Indigenous tribes were growing crops an astounding 8,000 years before those in the East and noticed how much larger their harvest was when corn, squash, and beans were grown in the same space.

In the 1970s, a new organic agriculture movement generated a resurgence of companion planting and the scientific study of it.

Why is companion planting so successful? Because it more closely reflects the relationship between plants in nature. What results are more genetically diverse plants with increased tolerance and resistance to conditions that would otherwise cause plant failure?

By positioning specific plants next to each other, they each contribute to a thriving plant community with visibly increased productivity. 

A common question in regard to this practice is “How close to my Oakleaf hydrangeas do companion plants have to be in order to get the benefits?”. 

Oakleaf varieties range in mature size, from 4ft to 8ft tall and wide. As a general rule, companion plants should be positioned just outside the zone of a hydrangea’s mature size. Regardless of how big it is when planted.

Do companion plants really work? Well, thousands of years of documented evidence strongly suggest that it does. So, how do the aforementioned benefits come into play?

What Are the Benefits

Pest control: Companion planting utilizes the natural food chain in the insect world to protect your Oakleaf hydrangeas from harm by attracting the beneficial pollinators that feed on destructive pests. 

These include ladybugs, praying mantes, ground beetles, and, of course, spiders.

Aphids, caterpillars, Japanese beetles, spider mites, slugs, and others are all deterred by the presence of these hungry landscape guardians.

Improved soil health: The natural pest control created by companion planting removes the need for harmful pesticide use in your garden. This prevents toxic elements from being absorbed into your soil.

This organic approach to healthy soil cultivation supports a thriving community of beneficial microbes and increases their numbers, thereby increasing the fertility and quality of your soil.

Why are microbes important? Because they do the work of converting nutrients inherent in the soil, and those applied through fertilization, into a form that is more easily absorbed by plants.

Companion plants tend to share resources (nutrients, moisture, etc.) and sometimes even generate resources themselves, as with nitrogen-fixing plants.

These plants take in nitrogen from the air and convert it into a form that they then can release into the soil around them. This is called ‘nitrogen fixation’.

Planting trees to shade your Oakleaf hydrangeas will provide sufficient shade and prevent soil moisture from evaporating too quickly (we’ll touch on the best companion trees in a moment). This maintains the preferred, moist environment for them while saving you on your water bill.

Increased yields: Minus the risk of pest infestations and the damaging effects of inhospitable growing conditions, plants are free to develop robust roots, branches, stems, and foliage.

Flowering plants, like Oakleaf hydrangeas, will experience a renewed vigor for bud and flower development. Each summer, an abundance of panicled white or pink blooms will cover your shrubs. 

Attracting butterflies, bees, and many other beneficial pollinators to ensure the cycle of companion planting benefits continues.

Consideration When Selecting Companion Plants

Also known as intercropping or plant association, effective companion planting around your oakleaf hydrangeas can include large and small trees, perennial shrubs (both evergreen and deciduous), flowering plants, herbs, and even fruiting shrubs, like berries. 

Blueberries, raspberries, boysenberries, and blackberries, among other types, all love acidic soil just as much as hydrangeas do.

All those benefits we talked about stand a much higher chance of being realized when you match the right companion plants to your hardiness zone, the variety of hydrangea you are growing and its mature size, the size of your planting location, and the amount of light in that location.

Keep in mind that plants and trees mature to various heights and therefore capture light from different angles. They also have roots with different growth habits (deep tap roots vs horizontal, sub-surface roots) which access water and nutrients at equally different levels. Awareness of this helps you position plants to their greatest benefit to each other.

Another key consideration is the growth rate of each plant you intend to pair with your Oakleaf Hydrangea. This rate will dictate their overall maintenance level. The most successful companion plants come with differing water, fertilizing, and pruning needs. So, be sure to match this to your maintenance preferences.

Best Companion Plants for Oakleaf Hydrangeas

Now, it’s time to talk about the best plants to pair with these blooming beauties. In addition to choosing companions that complement the care needs of your hydrangeas, look for ones that enhance the overall look of the border your shrub resides in.

These will be plants with contrasting shapes, leaf colors, flower and/or fruit shapes and colors, and finally, autumn color development on deciduous shrubs and plants.

Trees, Shrubs and Flowering Plants

Oakleaf hydrangeas make an excellent low-maintenance hedge plant, preferring well-draining, fertile, and, most importantly, acidic soil. Here are some luxurious shade trees including Japanese maples, Dogwood trees, and Tulip poplars, all of which are fantastic companions.

Hydrangea quercifolia or Oakleaf Hydrangea

They also provide the kind of dappled shade that allows for abundant blooming and consistently moist soil in warm weather. In addition to flowers that heighten your spring and summer show.

If your hydrangea is already positioned beneath existing trees, why not pair it with some complementary shrubs? 

Barberry Bushes, Dwarf Burning Bushes (Euonymus alatus ‘Compactus’), and, of course, boxwoods prefer similar growing conditions, while increasing the wow factor with contrasting foliage color and size.

Some have tiny flowers that twinkle like fairy lights around the large, panicled blooms of oakleaf hydrangeas. 

Barberry and Euonymus varieties display rich, burgundy foliage that offers dynamic appeal and dimension to your grouping and boxwoods add handsome, evergreen interest to your garden, right through winter.

Herbs and Flowers

Finally, we have some excellent, low-growing options to frame the front of your hydrangea shrubs that attract pollinators with their elegant flower clusters and eye-catching, ornamental foliage.

Why not plant a herb garden around your hydrangea? Non-woody herbs like parsley, cilantro, lemon balm, and basil thrive in a moist environment and don’t mind acidic soil.

Other colorful options include heuchera, coleus, scented geranium, and green or purple sweet potato vine. Mix and match to find your favorite combination!

Bad Companion Plants for Oakleaf Hydrangeas

Of course, there are many other options that may prove good companion plants for your Oakleaf hydrangeas. The specimens listed above are simply the ones that have been tested and have demonstrated their effectiveness in a controlled environment.

Naturally, there are going to be plants you’ll want to rule out. If a plant that piques your interest doesn’t meet the criteria listed at the top of this article, you can still grow them. Just not next to your hydrangeas.

The first is those that are not recommended for your hardiness zone. No matter how well these might do in other climates if they’re not suited to your area, they won’t survive.

The second factor is mature size. If you’re working with a limited planting space, of which most is taken up by your Oakleaf hydrangea, another large shrub may tip the scale and be more of a hindrance than a help.

The most important factor in a good companion plant is its similar light, water, and nutrient requirements.

Plants, shrubs, or trees that prefer dry, alkaline soil and full sun are not going to be successful choices. As their care needs fall on the opposite end of the spectrum from Oakleaf hydrangeas. These include Magnolia, Crepe Myrtle, Fruit Trees, lilac and camellia and spirea bushes, and deep shade plants like hostas, ferns, and hellebores.

Woody, Mediterranean herbs, like rosemary, lavender, and sage, and thyme, favor dry soil and a warm, temperate climate. So, these may not be good choices for that herb garden we talked about.

In order for living things to successfully occupy the same space, they must have similar preferences when it comes to their surroundings and requires similar environmental features in order to thrive.

Find out what plants make great companion plants for hellebores by clicking this link.

Citations

Oregon State University – Encouraging Beneficial Insects in Your Garden

Rogitex – Friends with Benefits – Companion Planting

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.