Rhododendrons are so well-behaved, carefree and fit so seamlessly into the landscape. Once planted and thriving, you might actually forget these shrubs are even there—until spring.
(Front) Rhododendron 'President Roosevelt', Rhododendron ‘Percy Wiseman’, Ophiopogon planiscapus 'Nigrescens' (Back) Acer shirasawanum 'Autumn Moon', Calocedrus decurrens. (All photos unless noted @Doreen Wynja)
Most of the year rhododendron shrubs hang out in the background. They provide impressive, sturdy structure and rich, often evergreen leafy texture to deep borders or along foundations. Or, as accent plants in island beds and along fences. Seemingly overnight, clusters of fat buds burst into a riot of color. With huge displays of flowers atop those familiar large, leathery leaves. And you suddenly remember why you layered these easy-to-grow shrubs into the garden in the first place. (And, look for places to add a few more).
Start by selecting the superior varieties that Monrovia chooses to grow. Then you'll be starting with varieties that have improved qualities, such as greater disease resistance and longer blooming. Nurtured at our nurseries with the right soil, water, and care by our craftsmen. Your rhododendrons will get off to a great start in your landscape, making these shrubs are easy and fuss-free. Here is what you need to know to grow rhododendrons in your garden.
Rhododendron Care: At A Glance
- Sunlight: Most rhododendrons prefer filtered sunlight, but some varieties can tolerate full sun in cooler climates.
- Soil: Plant in well-draining, acidic soil with a pH between 4.5 and 6.0. Add organic matter to improve texture and drainage.
- Watering: Provide consistent moisture during the first growing season, and water deeply during dry spells once established. Avoid waterlogged soil.
- Fertilizing: Apply a balanced or acidic fertilizer in early spring and after flowering to support healthy growth.
- Pruning: Remove dead or diseased wood as needed, lightly prune after flowering to control size and encourage root growth.
- Pests and Diseases: Watch for common issues like fungal diseases, insect infestations, and structural damage. Maintain a healthy growing environment and address problems promptly.
- Companion Plants: Choose plants with similar light and soil requirements to create a harmonious and long-lasting display.
What are Rhododendrons?
Rhododendrons are shrubs, often evergreen. They are either native to North America or hybrids grown for desirable attributes. For instance, height, color, and adaptability to regional climates. Their flowers are tubular-, funnel-, or bell-shaped—and depending on variety, can be fragrant.
With more than 900 known species in the genus. Plus, availability in a range of sizes, habits, and flower color. Rhododendrons are one of the most useful shrubs in the home landscape. Though we often speak of them as different groups of plants, rhododendrons and azaleas both belong to the genus Rhododendron.
While both stars in the landscape, Rhododendrons typically have much bigger flowers than azaleas. They bloom later, and are open and not as dense in their habit. (All good reasons to mix and mingle them in the landscape).
How to Choose the Best Rhododendron for Your Garden
With so many gorgeous varieties in a range of mature plant sizes and temperature tolerances from which to choose. Picking the right rhododendron for your garden can be a challenge. Here are the questions to ask and answer:
- What's my zone?
- How much planting space do I have?
- When do I most need color in the garden?
- What color speaks to me?
Here are the first two things to consider. Your hardiness zone and the ultimate amount of space available for the plant to grow. Most are hardy in zones 5 - 8. Though there are a some varieties that can take more chill (some are hardy to zone 4). Others can take a bit more heat (some are hardy to zone 9).
Rhododendrons range in size. From compact (perfect for containers, along a woodsy walkway or in front of taller shade lovers) to hedge height. (This is ideal under tall conifers, along property lines or to add a focal point). It's important to be realistic about how much space you have to fill. Choosing the right variety now will make life easier later.
Once you have figured out these two considerations. Your third decision is if would like one that blooms earlier or later in the season. Then finally (the most fun) choosing from a wide variety of colors. This can range from white, red, pink, purple, orange or yellow, depending on the specific variety.
Now you've selected the perfect plant for your landscape, there are just some things to know about planting and care. Rhododendrons are not especially fussy, but they do have needs. Finally, as these shrubs bloom over a relatively short season, it's good to add a few companions. Ones with similar light and soil requirements. This will keep the show going longer into late spring and early summer. More on all of this below...read on!
3 Compact Rhododendrons for Your Garden
Landmark Rhododendron
Compact midseason bloomer produces showy wavy-edged, deep fuchsia-pink flowers. Zone: 5 - 8. Learn more
PHOTO: Millette Photomedia
Cunningham's White Rhododendron
White flowers on a versatile landscape shrub for foundations and mixed borders. Zone: 5 - 8. Learn more
Bubblegum Rhododendron
Low, compact evergreen with bubblegum-pink, lightly scented flowers in spring. Zone: 5 - 8. Learn more
3 Rhododendrons for Colder Zones (4 - 9)
P.J.M. Rhododendron
5' tall with bright lavender-purple blooms that contrast with the small evergreen leaves. Zone 4 – 8.Learn more
Pink Rosebay Rhododendron
Spectacular late spring showy trusses of enchanting pink flowers on a vigorous, large shrub. Zone 4 – 9. Learn more
Nova Zembla Rhododendron
5' tall and wide with showy, bright red mid-spring flowers; thrives in cooler regions. Zone 4-8. Learn more.
PHOTO: Millette Photomedia
3 Rhododendrons for Warmer Zones (5 - 9)
Sneezy Rhododendron
Showy, soft pink flowers with red blotch on each bloom on a compact plant perfect for pots. Zone: 5 - 9.Learn more
Percy Wiseman Rhododendron
Lovely spring flowers emerge in shades of peach, pink, and cream on a versatile 4' tall shrub. Zone: 5 - 9. Learn more
PHOTO: GAP Photos/FHJ Greenmedia
President Roosevelt Rhododendron
Wow mix of variegated leaves and red flowers with white centers on useful 5' tall shrub. Zone: 5 - 9. Learn more
Where and When to Plant Rhododendrons
When it comes to planting rhododendrons, choosing the right location and timing is key to their success. Most rhododendron plants prefer filtered sunlight and acidic soil, but some modern varieties can tolerate a wider range of conditions, including full sun in cooler climates. Always check the plant tag for specific requirements and don't hesitate to ask your local garden center for advice if needed.
Consider these factors when selecting a spot for your rhododendrons:
- Light: Filtered sunlight is best, but some varieties can handle full sun in cooler areas.
- Soil: Rhododendrons thrive in acidic soil with a pH between 4.5 and 6.0. Apply aluminum sulfate if needed to lower the pH.
- Protection: In colder regions (Zone 4), planting near a windbreak can help protect your rhododendrons from harsh winter winds.
The best time to plant rhododendrons depends on your climate:
- Mild climates: You can plant rhododendrons year-round.
- Cold climates: Early spring is ideal, with early fall being a good second choice.
- Hot climates: Fall planting allows the plant's roots to establish during the cooler months.
Regardless of your climate, aim to plant when temperatures are cooler to allow the roots to establish before the stress of summer heat or winter cold. With the right location and timing, your rhododendrons will thrive and bring stunning blooms to your garden for years to come.
Soil Preparation for Rhododendrons
When you consider that native rhododendrons thrive in the dappled woodland shade and under trees with which they have grown. (Planting a young rhododendron under a mature tree is tricky and they often fail.) It is easy to understand their preference for moist, well-drained soils high in organic matter. Rhododendrons and azaleas have shallow fine hair-like roots and do not tolerate water-saturated soil conditions--but do require moist soils. Monrovia's rhododendrons are container-grown in a custom soil blend with added mycorrhizae. Therefore, once planted in the correct soil, they will naturally get off to a great start. If your soil lacks excellent drainage, amend prior to planting with a mix made for acid-loving plants.
How To Care For Rhododendrons
Once established in a location that suits their particular needs, rhododendrons are typically fuss free. They need only the basics--food, water, and pruning--to thrive.
- Watering: Because of those shallow roots plants need consistent water during the first growing season. If there is no rain, water deeply twice a week. In subsequent years, once plants are established, only dry periods (2 to 3 weeks without rain). Remember, many a rhodie has been felled by sitting in wet soils. So, always allow the soil to dry between waterings.
- Feeding: If your garden's soil isn't wonderfully rich or fertile, your rhododendrons will appreciate a balanced fertilizer. (If your soil is naturally acidic or a specialty acidic fertilizer if not.) Either way, the time to feed is when plant and again in early spring as flower buds swell.
- Pruning: Here's the good news. Rhododendrons neither need nor respond well to frequent hard pruning, so you can holster the clippers. However, pruning to remove dead or diseased wood at any time. Or, pruning lightly to control size after flowering will not harm your plant. After flowering deadhead by snapping off spent flower clusters to encourage root growth.
Protecting Your Rhododendrons from Common Pests and Diseases
Rhododendrons, while beautiful and beloved, can fall victim to various pests and diseases that can hinder their growth and vitality. It's important to be aware of these potential threats and take proactive measures to keep your plants healthy and thriving.
Some common issues to watch out for include:
- Fungal diseases like powdery mildew, leaf spot, and root rot
- Insect infestations from lace bugs, weevils, thrips, and aphids
- Structural damage caused by borers, leafminers, and caterpillars
The best defense against these problems is maintaining a healthy growing environment for your rhododendrons. Proper planting techniques, well-draining soil, and adequate sunlight and airflow can go a long way in preventing disease and deterring pests. Regularly inspecting your plants for signs of trouble and addressing issues promptly can also help mitigate damage and keep your rhododendrons looking their best.
6 Companion Shrubs for Rhododendrons for Near-Continuous Color
Part of the pleasure of having rhododendrons in your garden is how well they play with other acid-loving, filtered light, or semi-shade shrubs. Here are just a few spectacular (and unexpected!) plants to consider when building a bed, border, or focal point.
Enchanted Forest® River Nymph™ Pieris
Showy late winter buds open to white, bell-shaped flowers, followed by red new foliage. Zone: 6 - 8. Learn more
Bountiful Blue® Blueberry
Self-fertile, produces big crop of large, sweet, juicy berries on a compact, mounded shrub. Zone: 6 - 10. Learn more
Sparkler® Arrowwood Viburnum
Late-spring-to-early-summer creamy umbels give way to showy blue-black berries. Zone: 4 - 9. Learn more
Snow Queen Oakleaf Hydrangea
Midsummer's white flowers are held upright above oak leaf-shaped, evergreen foliage. Zone: 5 - 9.Learn more
Arnold Promise Witch Hazel
Wavy, fragrant yellow flowers on bare branches supply blazing color in late winter. Zone: 5 - 9. Learn more
Pink Dawn Viburnum
Put on a late winter to early spring show of fragrant, pink flower clusters on bare branches. Zone: 5 - 8. Learn more
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