Catawba rhododendron (Rhododendron catawbiense) is a multi-stemmed relative of the azalea that is grown mainly for its large clusters of lavender flowers. Its large, glossy evergreen leaves also add lush beauty to the landscape year-round.
This slow-growing shrub loves shade. Its shallow roots must be kept cool and moist in well-drained soil that does not hold water or become boggy. Happy rhododendrons can reach heights over 8 feet when mature. It is an ideal plant for woodland gardens, particularly those with excessive shade.
Do note, though, that all parts of this rhododendron shrub are toxic to humans and pets.
|Common Name||Catawba rhododendron, catawba rosebay|
|Botanical Name||Rhododendron catawbiense|
|Plant Type||Broadleaf evergreen shrub|
|Mature Size||6-8 ft. tall, 4-6 ft. wide|
|Sun Exposure||Partial shade to full shade|
|Soil Type||Fertile, well-drained|
|Bloom Time||Spring, summer|
|Hardiness Zones||4-8 (USDA)|
|Native Area||Southeastern United States|
|Toxicity||Toxic to people and pets|
Catawba Rhododendron Care
With its rounded habit, nice foliage, and colorful flowers, this shrub is impressive enough to function as a specimen plant in your landscape. Alternatively, you can plant several Catawba rhododendron shrubs together to create an attractive living privacy screen.
The Catawba rhododendron grows best in shaded areas because its sensitive root system does not like to be exposed to heat. Its roots should be kept cool and moist, but be careful to avoid wet feet—good soil drainage is essential to avoid root rot.
Moreover, this shrub's root system is shallow, so the roots can be easily damaged (for example, by weeding too vigorously around it and accidentally striking its roots with a shovel). Some of these concerns can be addressed by applying 3 inches of mulch around your Catawba rhododendron. A layer of mulch will:
- Reduce the amount of heat that permeates down to the root system
- Help retain moisture
- Cut down on weed growth and furnish a protective buffer between you and the root system
Prune your Catawba rhododendron just after it is done flowering. Tardy pruning could cause a reduction in flowers for next year.
Give Catawba rhododendron a little morning sun at the northern end of its range. At the southern end of its range, give it full shade.
Make sure that the soil for these shrubs drains well. If the soil does not currently drain well, amend the soil with organic matter.
Catawba rhododendron has average water needs, but try to keep its soil evenly moist without making the soil overly wet or boggy.
Temperature and Humidity
Catawba rhododendrons prefer cool temperatures and high humidity.
Fertilize Catawba rhododendron in spring yearly by working compost into the soil.
Start by pruning off dead or damaged branches just after your rhododendron has finished flowering. Next, trim off any branches that are sticking way up above the rest, thereby spoiling the overall shape of the bush. Yearly pruning will promote a more compact shape.
Propagating Catawba Rhododendron
These shrubs can be propagated using cuttings in late summer or early fall after new growth has begun to harden. Catawba rhododendron can be propagated through several methods. Here’s how:
- What You’ll Need: Healthy parent shrub, scissors, plastic bag, a sterile mix of 60% milled sphagnum peat moss and 40% perlite, containers, rooting hormone that contains a fungicide, and azalea fertilizer
- Where to Cut: Cut with scissors just below a node on a firm, hardened stem of this year's growth (cutting should be about 4 to 6 inches long).
- Maintaining the Cutting: Remove the bottom few leaves and any flower buds, dip the stem in water then in rooting hormone (if desired), and slide the stem about 2 inches into a container of mixed peat moss and perlite. Keep the cuttings warm and moist but not soggy. Fertilize monthly with azalea fertilizer. Rooting should take place in 3 to 4 months.
- When to Plant the Cutting: Transplant the cutting into the ground during the summer.
How to Grow Catawba Rhododendron From Seed
Growing rhododendrons from seed is time-consuming, but it can be done. Here's how:
- In February, sprinkle seeds on a small pot of equal parts moist sphagnum moss and perlite. Do not cover.
- Place the pot in a clear plastic bag to keep humidity high and keep away from direct sunlight in a warm location, rotating the pot once a week.
- The seeds will sprout in four to eight weeks and can be transplanted into other containers once they grow leaves. Keep the seedlings in containers for two years before transplanting them into the ground outdoors.
In temperate areas, no winter care is needed. However, if you live in a region that experiences freezing temperatures, it's a good idea to wrap your rhododendrons in burlap to protect them.
Common Pests and Plant Diseases
Black vine weevils and thrips are the most common insect pests of rhododendrons. These shrubs are also susceptible to a bacterial disease called crown gall. Fungal diseases that may affect rhododendrons include various cankers and gray mold.
How to Get Catawba Rhododendrons to Bloom
Catawba rhododendron blooms in mid to late Spring with large, rounded clusters of purple flowers. The blooms can last from two to seven months depending on climate. In colder climates, the bloom cycle will be much shorter. To extend bloom time, consider adding shade or frost protection, depending on when they flower (i.e. early or late in the bloom cycle). These plants will not always rebloom every year, and may go through periods of heavy blooms followed by a year of rest. To encourage blooming, necessary conditions should be met, such as ensuring your plant has enough light and is not given too much fertilizer. Note that young plants may not bloom right away. Make sure to prune your plant immediately after blooming, and deadhead the flowers to encourage new bud production.
Common Problems With Catawba Rhododendrons
While Catawba rhododendron is relatively easy to grow in the right environment, you may run into a few common growing problems.
Leaves Turning Yellow
Yellowing leaves often indicate soil that is too alkaline; rhododendrons need acidic soil. You can amend alkaline soil with various acidic additives like minerals and fertilizers.
If you notice wilting or drooping leaves, you may have waterlogged your plant. Make sure your soil is moist and well-drained, particularly if you live somewhere prone to heavy rains.
Does Catawba rhododendron work well in moon gardens?
If you are seeking shrubs for moon gardens and wonder if there is a white-blooming Catawba rhododendron, you are in luck. A cultivar of this popular flowering shrub with white flowers is Rhododendron 'Catawbiense Album'.
How long do Catawba rhododendrons live?
These robust shrubs can live to be 100 years old.
What are alternatives to Catawba rhododendrons?
If you're short on space, try planting azaleas. These small, compact cousins of rhododendrons offer beautiful blooms but take up less room. There are many types of azaleas to consider.
Azaleas and Rhododendrons. Poison Control.