Pests and Diseases

Growing Tree Hydrangeas (Panicle Hydrangeas)

Characteristics and Cultivation

Tree hydrangeas, also known as panicle hydrangeas (Hydrangea paniculata), are fast-growing flowering shrubs with an upright growth habit. They produce showy cone-shaped flower panicles in late summer when few other shrubs are in bloom. These panicles can reach up to 7 inches in length and feature clusters of small, creamy white blooms that gradually turn pinkish and eventually fade to tan or brown in the fall.

Tree hydrangeas are relatively easy to grow and can thrive in a variety of conditions. They are tolerant of pollution, salt, and urban environments. They prefer moist but well-drained soil with an acidic to neutral pH. These shrubs require full to partial sunlight, with some afternoon shade in hot climates.

Planting and Care

The best time to plant tree hydrangeas is in the spring or early fall. Choose a planting site with good drainage and protect the plants from strong winds, which can damage their stems.

Water tree hydrangeas regularly, especially during hot and dry weather. Avoid overwatering, as this can lead to root rot and other diseases. Fertilize the shrubs twice a year, once in early spring and again in the fall after the flowers have faded. Use a fertilizer formulated for shrubs and trees.

Pruning and Training

Tree hydrangeas can be trained to grow as small trees by judicious pruning. However, they achieve their best form when grown as large shrubs with multiple stems. Blooms occur on the current season’s growth, so prune as needed in the late winter to early spring. Untimely pruning can sacrifice some of the flowers for that growing season.

To train a tree hydrangea to grow as a tree, choose one main stem and secure it to a sturdy stake. Remove any competing ground stems and shoots that emerge from the main stem. Continuously check for shoots around the base of the plant and remove them as they appear. The main stem will eventually form a trunk-like structure.

Propagation

Tree hydrangeas can be propagated by cuttings. The best time to do this is in the spring or early summer before the plant begins to flower. Choose a healthy stem that has not yet flowered and cut off a piece that’s about 6 inches long. Remove the lower leaves and cut the remaining leaves in half. Dip the cutting in rooting hormone and plant it in a small container filled with vermiculite, coarse sand, or a combination of the two. Keep the soil moist but not soggy and place the container in a bright but indirect light. The cutting should develop a root system within a month.

Overwintering

To help tree hydrangeas through the winter, keep the soil moist right up until the ground freezes. Cover the roots with 3 to 4 inches of mulch, taking care to remove it as soon as the temperatures warm up.

Tree hydrangeas are generally resistant to pests and diseases. However, they can be susceptible to aphids, rose chafers, scale, slugs, and snails. Organic pesticides can be used to control these pests. Fungal diseases such as powdery mildew, blight, and leaf spot can also affect tree hydrangeas. These diseases can be treated with an appropriate fungicide.

Troubleshooting

Leaves Turning Black/Brown: This can be a sign of a fungal disease. Prune off the affected area or use a suitable fungicide.

Leaves Turning Yellow: This can indicate overwatering, underwatering, or a nutrient deficiency. Adjust watering practices and fertilize as needed.

FAQs

What is the difference between tree hydrangeas and hydrangea bushes?

Tree hydrangeas are shrubs that have an upright growth habit and can be trained into a tree-like form. Hydrangea bushes are typically shorter and more compact.

Can tree hydrangeas grow indoors?

Tree hydrangeas can be grown as container plants indoors, but they may not reach their full potential in terms of size and flowering.

How should I prune my tree hydrangea to encourage flowering?

Prune tree hydrangeas in the late winter to early spring, removing any dead or damaged stems. Cut back the remaining stems to about 6 inches above the ground. This will encourage the growth of new stems that will produce flowers in the summer.

Plant Overview

Eucalyptus trees, known colloquially as silver dollar trees or argyle apples, are evergreen trees native to Australia. They are characterized by their reddish-brown bark, silvery to blue-green leaves, and distinct menthol-like fragrance. Eucalyptus is a fast-growing tree that can reach heights of up to 60 feet in its natural environment, but when grown in home gardens, it typically remains smaller at around 6 to 10 feet tall.

Plant Care

Sunlight and Soil: Eucalyptus prefers full sun and well-drained soil. It can tolerate most soil types, but prefers slightly acidic to neutral pH levels.

Watering: Eucalyptus is somewhat drought-tolerant, but it does not like to be left dry for extended periods. Water your eucalyptus plant when the soil feels dry to the touch.

Fertilizer: If you are growing eucalyptus in the ground, it typically does not need fertilizer. However, container plants will deplete their nutrients more quickly, so fertilize them with a low-nitrogen houseplant fertilizer throughout the growing season.

Pruning: Eucalyptus trees generally do not need much pruning. However, you can prune overgrown, broken, or misshapen branches to keep the plant looking attractive. The best time to prune is in the summer, but avoid pruning during very humid weather.

Propagation

Eucalyptus trees can be propagated from seeds, cuttings, or grafting.

Growing from Seed: Eucalyptus seeds must be chilled in the refrigerator for two months before planting. Sow them indoors in late winter, about 10 to 12 weeks before your area’s last projected frost date. Once the seedlings are about 6 inches tall, they are ready to be transplanted outdoors.

Growing from Cuttings: The best time to take cuttings is when a tree is between 2 and 12 months old. To grow eucalyptus from cuttings:

Prepare a small pot of 3 parts composted tree bark to 1 part perlite. Add a slow-release fertilizer. Moisten the growing medium.

Use sterile pruning shears to cut a stem that is around 5 inches long with four to eight leaves. Cut just above a leaf node.

Remove the leaves on the lower half of the cutting.

Dip the cut end in a rooting hormone and plant it in the growing medium.

Keep the container in bright, indirect light and ensure the soil remains lightly moist.

Roots should form in about a month.

Common Pests and Problems

Eucalyptus plants are relatively free of major pests or diseases. However, you may occasionally spot eucalyptus long-horned borers, especially on stressed plants. Remove the infested area of the plant immediately, as insecticides are not effective against borers.

Eucalyptus trees can also develop leaf problems, such as brown leaves. This can be a sign of too little moisture or disease. If you notice brown leaves, check the soil moisture and look for any signs of disease.

Additional Tips

Eucalyptus is toxic to humans and pets, so it is important to keep it out of reach of children and animals.

Eucalyptus trees can be invasive in some areas, so it is important to check with your local authorities before planting one.

Eucalyptus is a fast-growing tree, so it is important to plant it in a location where it will have enough space to grow.

By following these tips, you can successfully grow and care for eucalyptus plants in your home or garden.

Pests and Diseases

Growing Tree Hydrangeas: A Comprehensive Guide

Growing Tree Hydrangeas (Panicle Hydrangeas)

Characteristics and Cultivation

Planting and Care

Pruning and Training

Propagation

Overwintering