Hydrangeas stand out as beloved and easily identified shrubs, celebrated for their stunning blooms. Within this extensive plant family, only a select few species are frequently cultivated in gardens. Among these, the Smooth Hydrangea (Hydrangea arborescens), also known as Wild Hydrangea, shines as a prominent choice.
These swiftly growing, bushy shrubs flourish when planted in autumn, typically not exceeding a height of five feet. They thrive in areas of partial sunlight and demand soil that drains well. It’s important to note that every part of the hydrangea plant poses a toxic risk to both humans and animals. Continue reading for detailed care and cultivation tips.
- Common Names: Smooth Hydrangea, Wild Hydrangea
- Botanical Name: Hydrangea arborescens
- Family: Hydrangeaceae
- Plant Type: Deciduous shrub
- Mature Size: Ranges from 3 to 10 feet tall
- Sun Exposure: Thrives in partial shade
- Soil Type: Prefers well-drained soil
- Soil pH: Adaptable to acid, neutral, and alkaline soils
- Bloom Time: Flowers in the summer
- Flower Color: Typically white
- Hardiness Zones: Suitable for zones 3-9 in the USA
- Native Area: Originates from the Eastern United States
- Toxicity: Parts of the plant are poisonous to both humans and pets
Smooth Hydrangea Care
For optimal growth, Smooth Hydrangea requires specific care conditions:
- Spacing: Ensure to plant shrubs with a minimum distance of five feet apart to allow ample room for growth.
- Light: These plants thrive in partial shade, avoiding the intense midday sun.
- Soil: They need soil that drains well to prevent waterlogging and promote healthy root development.
Light
Light requirements for Smooth Hydrangea (Hydrangea arborescens) include a preference for partial shade, ideally receiving filtered sunlight. While it can tolerate full sun, providing protection from the intense afternoon sun is crucial, especially in warmer southern climates.
Soil
Smooth Hydrangeas are versatile, capable of tolerating less-than-ideal soil conditions as long as the soil remains moist and well-drained. For optimal growth, they favor loamy, nutrient-rich soils with an acidic pH.
Water
In areas experiencing hot, dry summers or where the shrub is exposed to full sun in northern regions, Smooth Hydrangea requires additional watering throughout the growing season to maintain moist soil conditions. Applying a layer of mulch around the base can aid in moisture retention, ensuring the plant stays hydrated.
Temperature and Humidity
Smooth Hydrangeas are notably resilient to cold, making them one of the most cold-hardy varieties among hydrangeas, often not requiring extra protection during winter. Nonetheless, in especially frigid winters, they may experience dieback. These hydrangeas flourish in daytime temperatures around 70 degrees Fahrenheit throughout their growing period. They have a preference for humid environments over dry ones and should be shielded from strong winds for optimal health and growth.
Fertilizer
Smooth Hydrangeas benefit from a balanced, all-purpose fertilizer to support their overall health and growth. For gardeners aiming to enhance the quantity and size of blooms, a phosphorus-rich fertilizer, often marketed as “bloom boost” or with a nutrient ratio of 10-20-20, is recommended. Applying fertilizer in the spring is crucial for setting the stage for the growing season. However, it’s important to avoid over-fertilization, as excessive nutrients can harm the plant by burning the foliage or promoting leaf growth at the expense of flowers. Unlike Big Leaf Hydrangeas, the flower color of Smooth Hydrangeas is not affected by changes in soil pH.
Types of Smooth Hydrangea
The Smooth Hydrangea (Hydrangea arborescens) boasts several captivating cultivars, each offering unique characteristics and visual appeal. Among the notable varieties are:
- Incrediball Hydrangea (‘Hydrangea arborescens ‘Abetwo’ Incrediball): Known for its large, striking flowers and sturdy, upright stems, this cultivar is a standout for its impressive blooms.
- Invincibelle Spirit Hydrangea (‘Hydrangea arborescens ‘NCHA1′ Invincibelle Spirit’): Distinguished by its pink blooms, a departure from the more traditional white, this cultivar adds a vibrant splash of color.
- Hayes Starburst Hydrangea (‘Hydrangea arborescens ‘Hayes Starburst’): This cultivar is celebrated for its unique double blooms that provide a stunning visual contrast to the standard white flowers typically seen in Smooth Hydrangeas.
Pruning
Pruning Smooth Hydrangeas is straightforward due to their ability to bloom on new growth. To encourage vigorous stem growth and consistent flowering, these plants can be cut back to the ground each winter or early spring. As an alternative approach, you can also selectively remove any stems that are weak, damaged, or diseased to maintain the plant’s health and appearance.
Propagating Smooth Hydrangea through cuttings, either root or stem, is an effective way to grow this fast-expanding plant. Here’s how to propagate softwood cuttings, ensuring the plant is not under patent protection:
- Cutting Preparation: Snip a 5-inch piece from a healthy stem, removing any leaves near the cut end to prevent rot.
- Rooting Hormone: Lightly coat the cut end in rooting hormone to encourage root growth and protect against fungi.
- Planting Medium: Plant the cutting in a sterile, well-draining medium like damp sand or vermiculite. Ensure the medium stays moist but not waterlogged.
- Covering: Place a plastic cover over the cutting to maintain humidity. Make sure the plastic doesn’t touch the leaves to avoid mold or rot.
- Location: Keep the cutting in a spot with bright, indirect sunlight. The area should be warm but not in direct sunlight to prevent overheating.
- Watering: Water the medium whenever it begins to dry out, keeping it consistently moist to support root development.
- Root Growth: Roots typically start to form within a few weeks, after which the cutting can be transplanted into a more permanent location.
By following these steps, you can successfully propagate new Smooth Hydrangea plants to expand your garden or share with fellow gardening enthusiasts.
Overwintering
As winter approaches, Smooth Hydrangeas enter a dormant phase. To ensure their survival and health through the cold months, particularly for those grown outdoors, certain overwintering precautions are necessary:
- Outdoor Plants: It’s crucial to wrap and cover outdoor Smooth Hydrangeas to safeguard the plant and its root system from freezing temperatures. Use burlap or a frost cloth to wrap the plant, and consider mulching heavily around the base to insulate the roots.
- Potted Hydrangeas: For hydrangeas grown in pots, moving them indoors or into a greenhouse provides protection from the cold. This step is especially important in regions where temperatures drop below the freezing point.
- Watering: During winter, while the plant is dormant, minimize watering to once a month. This is sufficient to keep the roots moist without over-saturating the soil, which could lead to root rot in the cold.
- Spring Revival: As the weather warms up in spring, gradually reintroduce outdoor plants to more frequent watering and remove any protective coverings. Potted plants can be moved back outside once the threat of frost has passed, easing them back into the growing season.
By following these overwintering steps, you’ll help your Smooth Hydrangeas survive the winter and return to vigorous growth and blooming in the spring.
Common Pests & Plant Diseases
Smooth Hydrangeas are generally robust and face few serious pest or disease issues. However, vigilance is necessary to ensure they remain healthy. Some common pests and diseases to watch for include:
- Aphids: These small, sap-sucking insects can cluster on the undersides of leaves and stems, weakening the plant by draining its fluids.
- Japanese Beetles: These beetles are known for their voracious appetite, feasting on the leaves of hydrangeas and leaving behind skeletonized foliage.
- Spider Mites: Tiny but troublesome, spider mites can cause damage by puncturing plant cells to feed. They often leave behind fine webs on the plant.
- Powdery Mildew: This fungal disease thrives in humid conditions, coating leaves in a white, powdery substance. It can hinder photosynthesis and weaken the plant.
To manage these pests and diseases, consider the following:
- Regular Inspection: Check your plants frequently for signs of pests or disease, allowing for early intervention.
- Proper Watering: Water plants at the soil level to avoid wetting the foliage, which can help prevent powdery mildew.
- Adequate Spacing: Ensure plants have enough space between them to improve air circulation, reducing the risk of powdery mildew and making it harder for pests to spread.
- Natural Predators: Encourage beneficial insects like ladybugs and lacewings, which prey on aphids and mites, by planting a diverse garden.
- Fungicides: For severe cases of powdery mildew, a fungicide may be necessary. Choose a product suitable for hydrangeas and follow the application instructions carefully.
By adopting these practices, you can help your Smooth Hydrangeas stay healthy and vibrant, minimizing the impact of common pests and diseases.
How to Get Smooth Hydrangea to Bloom
Smooth Hydrangeas are known for their generous flowering period, which spans throughout the summer, showcasing lush blooms.
Characteristics of Smooth Hydrangea Blooms
- Appearance: They produce clusters of small, white flowers that come together to form heads up to 12 inches wide, offering a visually striking display.
- Fragrance: The blooms emit a sweet scent, which is not only pleasant for garden visitors but also attracts a variety of pollinators.
Tips for Encouraging More Blooms
- Pruning: Annual pruning in late winter or early spring is crucial. Since Smooth Hydrangeas bloom on new wood, cutting back the plants helps stimulate growth of new stems that will bear flowers.
- Sunlight: Ensuring the right balance of light is key. While they thrive in partial shade, too much shade can reduce flowering. Ensure they receive dappled sunlight or morning sun with afternoon shade, especially in hotter climates.
- Fertilization: Avoid fertilizers high in nitrogen, which can lead to lush foliage at the expense of blooms. Instead, opt for a balanced fertilizer or one slightly higher in phosphorus to promote more blooms.
By following these guidelines, you can maximize your Smooth Hydrangea’s blooming potential, creating a stunning display of flowers throughout the summer.
Common Growing Problems
When cultivating Smooth Hydrangea, you might encounter a few typical growing challenges. Recognizing and addressing these issues early can help ensure the health and beauty of your plant.
Yellowing Leaves
- Cause: Yellow leaves often indicate a nutrient deficiency, commonly a lack of chlorophyll production related to insufficient iron.
- Solution: Apply an iron-rich fertilizer and maintain acidic soil conditions to enhance iron availability to the plant.
Drooping Leaves
- Cause: Leaves may droop due to overwatering or excessive sun exposure, both of which stress the plant.
- Solution: Monitor and adjust watering practices to ensure the soil is moist but not waterlogged, and provide the plant with partial shade, especially in hot climates, to prevent sun stress.
Hydrangea Not Blooming
If your Smooth Hydrangea isn’t blooming, there could be several reasons, including:
- Improper Pruning: Pruning at the wrong time of year can remove flower buds.
- Too Much Shade: Insufficient sunlight can inhibit blooming.
- Nutrient Imbalance: Excessive nitrogen encourages leaf growth at the expense of flowers.
- Winter Kill: Cold winter temperatures can damage or kill flower buds.
- Age of Plant: Very young plants may not bloom prolifically until they are more established.
- Drought Stress: Insufficient water during bud formation can reduce blooming.
- Improper Fertilization: Using the wrong type of fertilizer can discourage flowering.
- Pest or Disease Pressure: Pests or diseases can stress the plant, affecting its ability to bloom.
Addressing these specific issues with appropriate cultural practices and care will help overcome common growing problems and encourage your Smooth Hydrangea to flourish.
How do I plant Smooth Hydrangea?
A: Plant Smooth Hydrangea in the fall or early spring. Choose a location with partial shade and well-drained soil. Dig a hole as deep and twice as wide as the root ball, place the plant in the hole, backfill with soil, and water thoroughly.
When is the best time to prune Smooth Hydrangea?
A: The best time to prune is late winter or early spring before new growth begins, as Smooth Hydrangea blooms on new wood. Pruning encourages fresh growth and more abundant blooms.
How often should I water Smooth Hydrangea?
A: Water newly planted hydrangeas regularly to keep the soil moist but not soggy. Once established, they require less frequent watering, but it’s important to maintain moisture during dry spells.
What type of fertilizer is best for Smooth Hydrangea?
A: Use a balanced, all-purpose fertilizer in early spring. To encourage more blooms, select a fertilizer higher in phosphorus. Avoid high nitrogen fertilizers, which can promote leaf growth over blooms.
Can Smooth Hydrangea grow in full sun?
A: While they can tolerate full sun in cooler climates, Smooth Hydrangeas prefer partial shade, especially protection from the hot afternoon sun in warmer regions.
Why are my Smooth Hydrangea’s leaves turning yellow?
A: Yellow leaves can indicate a nutrient deficiency, often iron. Use an iron-enriched fertilizer and ensure the soil is acidic enough to improve nutrient uptake.
Can I grow Smooth Hydrangea in a pot?
A: Yes, Smooth Hydrangea can be grown in large pots with drainage holes. Use a well-draining potting mix and ensure the pot is large enough to accommodate growth.
How do I propagate Smooth Hydrangea?
A: Propagate by taking softwood cuttings in early summer. Cut a 5-inch stem, remove the lower leaves, dip in rooting hormone, and plant in a well-drained medium. Keep moist and covered with plastic until roots develop.
Is Smooth Hydrangea toxic?
A: Yes, all parts of the Smooth Hydrangea are toxic to people and pets if ingested, so it’s important to plant them away from play areas and monitor pets and children around the plants.
How can I encourage my Smooth Hydrangea to bloom?
A: Ensure your plant is in a location with appropriate light, avoid high nitrogen fertilizers, and prune correctly in late winter or early spring to encourage blooming on new growth