Companion Plants for Azaleas | Good and Bad

Azaleas (Rhododendron) are flowering shrubs that add color and fragrance to any garden. Their long-lasting, bright blooms can be pink, purple, yellow, red, orange, or white. 

These are notoriously easy to care for but introducing companion plants for Azaleas will improve their health and appearance even more. 

That said, not every plant will make a good companion for azaleas, and selecting the best species can be a little challenging. 

To make it much easier, this article provides you with all the information you need to choose the perfect companions for your azaleas.  

Companion Planting Explained

Companion planting is the practice of growing different species of plants in close proximity to one another, in such a way they will provide mutual benefits. This can range from enhanced growth to protection from pests to improving soil conditions. 

Companion planting is a natural and organic method of growing that removes the need to use any chemical-based pesticides, herbicides or fertilizers. Companion planting is also cost-effective and time-efficient, making it a very popular gardening technique. 

A perfect example of companion planting called the “Three Sisters” method was first practiced thousands of years ago by Native American tribes. This method was so successful that it is still widely used today.

The Three Sisters method is used to grow squash, sweetcorn, and beans. The huge leaf canopy of the squash plant provides shade to the sweetcorn and beans, as well as suppresses the growth of weeds.

The sweetcorn acts as a natural support structure for the beans to climb up. The beans, like all legumes, fix nitrogen from the air into the soil. This nitrogen can be used by the squash and sweetcorn to help them grow.

Benefits of Companion Planting

The practice of companion planting offers a huge variety of benefits. As well as being advantageous to the plants themselves, this organic growing technique also improves local biodiversity by attracting wildlife. 

Some of the main benefits of companion planting are: 

Pest Control: Many people are becoming more conscious of the negative impact chemical-based pesticides have on the environment and our health. Companion planting, however, uses biological pest control. 

Some strongly scented plants such as onions and lavender, naturally repel insects through their fragrance. They can also be used to mask the scent of host plants that pests may otherwise be attracted to. 

Certain plants attract predatory insects that prey on pest insects. For example, ground beetles feast on a variety of invertebrate pests including ants, caterpillars, and slugs. Allowing these pests to feast on your azaleas can diminish plant health and lead to chlorosis. 

Improved Soil Health: The quality and condition of soil have a huge impact on the health and growth of your plants. Deep-rooted species, like asparagus, help to break up the soil making it less compact and well-draining.

Legumes are great companion plants because they are nitrogen fixers. They take nitrogen from the air and convert it into a form that is fixed in the soil. Nitrogen is essential for plant growth and in its fixed form can be used by neighboring plants. 

Increased Yields: Companion planting was traditionally practiced as a way of maximizing crop yields. It can increase both the size of the crop and the amount of produce as the result of a combination of factors, including increasing pollination, improving growth, and reducing pest attacks. 

Improved Flavor: With the correct planting combination, it is possible to improve the flavor of fruits, vegetables, and herbs. Growing your own produce is rewarding and even more so when you can enhance the taste. 

For example, basil improves the flavor and growth of tomatoes, borage sweetens strawberries, and the taste of broccoli can be enhanced by onions and celery. 

Attracts Pollinators: Pollinators are essential for the survival of the human race; therefore, it is in our best interest to attract as many pollinators to our gardens as we can. Nearly 90% of all plant species are pollinated by animals such as bees, birds, and butterflies. 

Brightly colored and highly scented plants are typically most attractive to pollinators. These types of plants also provide vibrancy and fragrance to gardens. 

Eco-Friendly: By practicing companion planting you are reducing the use of chemical-based pesticides, herbicides, and fertilizers which are harmful to wildlife and our health. 

Companion planting also requires species to be planted close together. This saves water by reducing evaporation and keeping the soil moist. 

Considerations when Selecting Companion Plants

Although companion planting is highly beneficial, you will only reap the rewards if you use the correct combination of plants. There must be some consideration when selecting companion plants as poor pairings can actually have negative effects. 

It is important that your chosen plants have the same growing conditions in order to work well together. For instance, a plant that requires full sunlight should not be planted with a shade-loving species because the conditions would have adverse effects on one or both of the plants. 

Whilst companion planting can provide a visually interesting display, you should think about the size and growth rate of each species. For example, tomato plants grow tall and rapidly, which can shade out smaller plants below.  

You should also think about what is happening below the surface. Deep-rooted plants have a tendency to steal moisture from shallow-rooted plants which lack taproots and root hairs. This can hinder the growth and development of shallow-rooted plants as they become deprived of water. 

The worst companion plants are allelopathic species. They produce compounds that inhibit the growth, development, and survival of neighboring plants. Allelopathic plants include elderberry and black walnut. 

Good Companion Plants for Azaleas

Azaleas grow best in cool locations that offer shelter from the wind and partial shade. These plants have shallow roots that require acidic soil (4.5 to 6.0 pH) that is moist but well-drained. Both indoor and outdoor azaleas are easy to grow and require minimal maintenance. 

All varieties and parts of azalea plants contain grayanotoxins which are poisonous. As such, they are planted for ornamental purposes due to their large, colorful blooms. The funnel-shaped flowers are fragrant. 

The vibrant flowers of azaleas bloom between March and June and make for an eye-catching addition to any garden, returning annually. Regular pruning can keep these plants small and neat, but some species can grow huge, reaching heights of over 20 feet. 

A variety of low-growing plants, shrubs, and trees can be planted alongside azalea. Here are some great examples of companion plants for azaleas:   

Herbs and Flowers

Hydrangea: Just like azaleas, hydrangeas thrive in acidic soil. They make an excellent companion plant not only because they boast vibrant blooms in an array of colors during the summer, which nicely complements any azalea plant, but they are also very attractive to pollinators including bees, butterflies, and hummingbirds. 

Mountain Laurel: A member of the heath family alongside azaleas, mountain laurels grow best in acidic soil and cool, partially shady conditions. Mountain laurels have thick and glossy leaves that repel foragers such as rabbits and deer, helping to protect your azalea. They are also suitable companion plants for Japanese Maples

Barberry: This shrub requires the same growing conditions as azaleas, making it the perfect companion. It boasts red and gold berries during the winter when azaleas are bare. The berries also attract pollinators. Barberries can be easily cultivated as hedgerows or boarders. 

Spotted Dead Nettle: Also called beacon silver due to its green and silver leaves, the unusual foliage of this plant really makes the azalea flower pop. The spotted dead nettle is a great ground cover plant as it fills out bare and empty spaces, making it a great azalea companion plant. 

Holly: The dark green leaves and vibrant red berries of holly make an attractive contrast to an azalea. Holly also grows best in acidic, well-draining soil. The spikey holly leaves deter birds from feasting on the blooms and seeds of your azalea. 

Snowball Bush: As suggested by its name, this plant features white balls of blossom that resemble snowballs. They are easy to grow and require the same acidic and partially shady conditions that azaleas need. The snowball bush is also fairly resistant to foraging by animals. 

Witch Hazel: From small trees to huge bushes, witch hazel comes in a range of sizes. During the fall their foliage becomes a golden color. This works well with azaleas since they lose their leaves during the fall and winter. 

Bleeding Hearts: Tall growing azaleas provide the shade that bleeding hearts need to thrive. This plant dies back in the summer, making room for your azalea to bloom. When bleeding hearts bloom in the spring, they produce pink, heart-shaped flowers, hence the name. 

Bleeding Heart Flowers
Credit: Rizka by CC: 4.0

Plantain Lily: These shade-tolerant plants have eye-catching striped leaves and produce elegant flowers. They are resistant to slugs and snails, helping to keep them away from your azaleas. Plantain lilies also have thick foliage which prevents weeds from growing. This can be beneficial if your azaleas are competing with weeds for nutrients and space. 

Summer Sweet: Although called the sweet pepperbush, this plant makes a great companion to azaleas as they have similar growing conditions. The pale, fragrant flowers attract pollinators. Summersweet can be grown alongside streams to delay erosion. 

Japanese Andromeda: These plants, like azaleas, require acidic soil and protection from the sun. Similarly to azaleas, the flowers and leaves of Japanese andromeda are poisonous. 

Fruits and Vegetables 

Blueberry: Although blueberries prefer full sun, they are capable of thriving in shady conditions too. Companion planting blueberries with azaleas makes perfect sense because they both do best in acidic soils and the blueberry shrub will entice a variety of bee and butterfly pollinators. 

Cranberry: Another acidic-loving crop is cranberry. Like azalea, this plant favors dappled shade with humus-rich, moist soil. 

Bad Companion Plants for Azaleas

Although azalea has a lot of great companion plants, there are a few species that should e avoided because of the detrimental effects they can have on your azaleas.

Here is a list of plants to avoid when thinking about companions for your azalea: 

Lavender: Lavender is a fragrant, purple herb that requires contrasting environmental conditions to azaleas. Lavender loves alkaline soil whilst azalea needs acidic soil. Additionally, lavender needs arid conditions to grow whereas azalea is like moist soil. Finally, lavender grows best in full sun, but azaleas prefer shade. 

Lavandula angustifolia
Credit: Laslovarga by CC: 4.0

Black Walnut: Very few plants grow well near the black walnut tree, especially azaleas. This allelopathic tree produces a chemical called juglone, which hinders the growth and development of many species. Azaleas are especially sensitive to juglone. 

Eggplants: This fruiting plant likes it very hot, but azaleas prefer much cooler climates. Moreover, eggplants are deep-rooted meaning they may rob the shallow-rooted azalea of nutrients from the soil. 

Citations 

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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.