How to Grow Rhododendron

Co-authored by Lauren Kurtz

Last Updated: April 9, 2024 References

Rhododendrons are ornamental shrubs with bell-shaped flowers and wide, evergreen leaves. They can be difficult plants to grow as they require specific conditions to flourish. Rhododendrons prefer well-draining, acidic soil and thrive in dappled shade with mild temperatures. To grow your own rhododendron, plant your shrub in mild weather and care for it regularly. As long as you give your plant plenty of attention, you can grow luscious, healthy rhododendrons!

Part 1

Part 1 of 3:

Finding a Planting Location

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Plant your rhododendron in spring or early fall. Although you can grow rhododendron during any time of the year, they adapt best when planted in mild weather. In hot climates, early fall is preferred but in cold climates, aim for springtime.^{[1]
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- Early fall is ideal so your plant has time to grow a root system before winter.
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Find a spot with dappled shade. Rhododendrons thrive in areas with an equal amount of sunlight and shade every day. Choose a spot with your garden that gets both shade and sunlight a day, avoiding both deep shade and full sun.^{[2]
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- Rhododendrons planted in excessive shade usually flower less.
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Because they have delicate roots, rhododendrons need well-draining soil to get enough nutrients and avoid becoming waterlogged. To test its draining levels, dig a 12 inches (30 cm) hole in the soil and fill it with water, timing how long it takes to drain. If the soil takes between 5-15 minutes to drain, it is suitable for rhododendrons.
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Pick acidic soil to grow your rhododendron in. The ideal acidity for your soil is 4.5-5.5 pH. You can find the soil's pH level by buying a pH soil test kit from a nursery or getting it professionally tested.^{[3]
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- To raise the soil's acidity, you will need to amend the soil by mixing pine needles, sphagnum peat, sulfur, and organic mulches.
- If you have tried amending your soil and it is still too alkaline, you may want to pick a different flowering shrub, such as lilac.
Rhododendrons can be damaged or even killed by strong winds. To protect them from unexpected storms, choose a spot near a building, hedgerow, or fence.^{[4]
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Part 2

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Planting Rhododendron

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Buy healthy rhododendron plants or cuttings. When visiting your plant nursery, choose rhododendrons that are a deep green, and avoid yellowing or wilted plants. You can also take stem cuttings from existing rhododendrons and plant them to grow a new plant.^{[5]
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- Most amateur gardeners do not grow rhododendrons from seed, as they take between 2-10 years to flower.^{[6]
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- If you grow cuttings, you will need to grow the cuttings for 1-2 weeks in water so they can develop roots.
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Water your rhododendron and loosen the roots before you plant it. Water the rhododendron plant, then make 2 inches (5.1 cm) cuts into the root ball equally spaced around the sides. Use your hands to loosen the root ball and pull roots near the cuts outward.^{[7]
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- This stimulates your rhododendron's root growth and helps it absorb water and nutrients.
If you are planting multiple rhododendrons, place them between 2–6 feet (0.61–1.83 m) apart depending on the plants' sizes. Give the rhododendron at least that much space from other plants if you are only planting one.^{[8]
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Set the rhododendron into the hole with its roots at soil level. Dig a hole twice as wide as the root ball and as deep. Set the plant into the soil, positioning it so its roots are approximately at soil level.^{[9]
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- Planting the rhododendron below soil level can cause root rot.
Fill the hole back up with soil halfway, then water the rhododendron to help the soil settle. When you've finished watering, fill the rest of the hole with soil.^{[10]
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Part 3

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Caring for Rhododendron

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Water your plant every day for the first year. New rhododendrons need daily watering to stay healthy. After the first year, the plant should be able to get moisture on its own unless the rainfall is less than 1 inch (2.5 cm) a week.^{[11]
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- The soil surrounding your rhododendron should be moist, but not damp or watery. Overwatering your plant can cause root rot and other diseases.
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Mulch your rhododendron once a year. Mulching your plants protects its root system and keeps the soil moist. Apply 2–5 inches (5.1–12.7 cm) of an acidic mulch or compost to the soil surrounding your plant, preferably made with pine wood chips or needles.^{[12]
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- Keep the mulch 1–2 inches (2.5–5.1 cm) away from the rhododendron's trunk.
- You can purchase acidic mulches at most plant nurseries or garden centers.
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Fertilize your rhododendron every spring. Whether your rhododendron is a spring or fall bloomer, fertilize your rhododendron annually in springtime. Spray or apply a light coating of fertilizer to the rhododendron, as a heavy application can burn it.^{[13]
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- Rhododendrons thrive best if you use fertilizers with high nitrogen, phosphorus, magnesium, iron, and calcium. Look for fertilizers that are specifically labeled for rhododendrons and azaleas for the best results.^{[14]
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Wrap your rhododendron in burlap to protect them from harsh weather. Rhododendron shrubs need protection from snowfall and cold weather. Wrap your rhododendron branches lightly in burlap and secure it with twine.^{[15]
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- Plan on wrapping your rhododendron in late autumn before the first frost.
young rhododendrons in springtime. Prune your rhododendron in early spring for the first 1-2 years after planting it. Pruning established plants can prevent them from blooming for several years, so let older rhododendrons grow naturally beyond cutting back 1 or 2 branches a year.

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Question

What is likely to grow roots faster: a young rhododendron stem or an old, thick, sturdy one? And how long before they grow roots?

Lauren Kurtz
Professional Gardener
Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.

Lauren Kurtz

Professional Gardener

Expert Answer

A young stem will root faster. An old thick stem is unlikely to produce roots. Propagating a rhododendron from a cutting requires careful conditions and patience. It can take 3 to 4 months for a cutting to grow roots. Take a cutting from new growth in the early fall or spring.

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After I planted my rhododendron, I realized my soil is clay. What I need to do to correct the situation?

Ninox

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The best is to dig all around the plant and remove it from the ground. Then you can add sand in the hole and mix it with the clay.

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When do I cut the dead heads of rhododendrons?

Ninox

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Cut dead wood in the late summer. That way, the plant will produce more flowers the following year.

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Rhododendrons come in a variety of species and hybrids. To choose the best variety for your climate, flower color, plant height, and other factors, you can access the American Rhododendron Society's species database at https://www.rhododendron.org/search_intro.asp

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