Hydrangeas and rhododendrons are two popular garden plants many people use for landscaping. These plants have bright and beautiful flowers.
What is the difference between hydrangea and rhododendron? Hydrangea’s color changes depending on the soil’s pH, but rhododendron flower color is not affected by the pH of the soil.
Key Areas Covered
1. What is Hydrangea
– Definition, Features
2. What is Rhododendron
– Definition, Features
3. Similarities Between Hydrangea and Rhododendron
– Outline of Common Features
4. Difference Between Hydrangea and Rhododendron
– Comparison of Key Differences
5. FAQ: Hydrangea and Rhododendron
– Answers to Frequently Asked Questions
Key Terms
Hydrangea, Rhododendron
What is Hydrangea
Hydrangea is a group of over 70 different types of flowering plants found in Asia and the Americas. The largest variety of hydrangeas can be found in places like China, Korea, and Japan. Most hydrangeas are shrubs that grow between 1 to 3 meters tall. But some can be small trees, and others are vine-like plants that can climb up to 30 meters by using trees for support. They can be either deciduous or evergreen.
Hydrangeas bloom from early spring to late autumn. Their flowers grow in clusters, often at the tips of the stems. There are usually two types of flowers in these clusters: small, less noticeable ones in the center, and larger, showy flowers with colorful petals around the edges. One interesting thing about hydrangeas is that their flower color can change depending on the soil’s pH level. If the soil is more acidic (with a pH of 5.5 or lower), the flowers will be blue. If the soil is more alkaline (with a pH of 6.5 or higher), the flowers will turn pink. Soil with a pH between 5.5 and 6.5 will produce purple flowers.
What is Rhododendron
Rhododendron is a type of plant that includes shrubs and small to sometimes large trees. Some are as short as 10 cm tall. However, the biggest species can grow up to 30 meters high. Their leaves come in many sizes, ranging from 1 cm to over 50 cm, and can either stay green all year or fall off in certain seasons. In some species, the underside of the leaves is covered with tiny scales or hairs.
Rhododendrons are known for their beautiful clusters of large flowers, with one species in New Guinea having flowers up to 15 cm wide. Some rhododendrons are small and grow in cold, alpine areas, while others grow in warmer, tropical places and can even live on other plants like epiphytes.
These plants also have some special traits. Their flowers are grouped together, they have dry, thin coverings around the buds, and their fruit is a capsule that splits open when ripe.
Similarities Between Hydrangea and Rhododendron
- Both are flowering plants known for their large, colorful blooms.
- They are commonly used in landscaping for their attractive flowers and foliage.
- They prefer well-drained soil for healthy growth.
Difference Between Hydrangea and Rhododendron
Definition
- Hydrangea is a plant with big, colorful flowers that can change color depending on the soil while rhododendron is a plant with bright flowers that can grow as tall shrubs or small trees.
pH Sensitivity
- Hydrangeas tolerate soils with a higher pH and their flower color changes based on soil pH, but rhododendron flower color is unaffected by soil pH.
Size
- Some rhododendrons can grow very large, reaching up to 20 feet or more. Hydrangeas generally grow up to 8 feet unless they are climbing varieties.
Shape
- Hydrangeas tend to spread out as wide as they are tall, sometimes slightly wider, whereas rhododendrons are typically slightly taller than they are wide.
Soil Tolerance
- Rhododendrons do not tolerate constantly moist soil. Meanwhile, hydrangeas prefer water but need well-drained soil and do not tolerate “wet feet.”
FAQ: Hydrangea and Rhododendron
1. What is the difference between a rhododendron and an azalea?
The main difference is that rhododendrons usually have larger leaves and flowers, while azaleas tend to have smaller, thinner leaves and blooms. Also, most azaleas are deciduous, meaning they lose their leaves, but many rhododendrons are evergreen and keep their leaves year-round.
2. What are rhododendrons confused with?
Rhododendrons are often confused with azaleas, because they are closely related and look similar. They can also be mistaken for mountain laurels and some types of laurel bushes due to their similar flower shapes.
3. What makes hydrangeas different colours?
Hydrangeas change color based on the pH level of the soil. If the soil is acidic (pH below 5.5), the flowers turn blue. If the soil is neutral to alkaline (pH above 6.5), the flowers become pink.
4. How do I identify a rhododendron?
Rhododendron has thick leaves that are usually dark green. They have big clusters of flowers that can be of various colors, such as pink, purple, or white. The flowers have five petals and often have a funnel shape.
5. What are the disadvantages of rhododendrons?
Rhododendrons have several disadvantages. They require well-drained, acidic soil and can suffer from root rot if the soil doesn’t drain properly. Some varieties grow quite large, which may not be suitable for smaller gardens. Additionally, rhododendrons are vulnerable to pests and diseases, such as aphids and leaf spots.
Reference:
1. “Hydrangea.” Wikipedia. Wikipedia Foundation.
2. “Rhododendron.” Wikipedia. Wikipedia Foundation.
Image Courtesy:
1. “Hydrangea flowers2” by (CC BY-SA 4.0) via Commons Wikimedia
2. “Rhododendron sp. 027” by Kor!An (Андрей Корзун) (CC BY-SA 3.0) via Commons Wikimedia
