Hydrangea arborescens (hy-DRAIN-juh ar-bo-RES-senz ) smooth hydrangeas are deciduous native plants to the eastern United States and a member of the hydrangea family Hydrangeaceae (hy-drain-jee-AY-see-ee).
Wild hydrangeas’ natural environment is along stream banks, in ravines, and moist, rocky wooded slopes.
You’ll find this attractive wild plant growing naturally throughout North America:
- New York
The genus name originates from the Latin word ‘hydor’ meaning water.
‘Aggeion’ meaning vessel referring to the cup-like seed capsules the plant produces at the end of its blooming season.
‘Arborescens’ comes from the word ‘arbor’ meaning tree. This is because the shape of the shrub is like a small tree.
Common names include:
- Spreading hydrangea
- Smooth hydrangea
- Wild hydrangea
- Seven Bark
Hydrangea Arborescens Care
Size & Growth
Although this plant typically grows to be 3′ to 5′ feet high and wide. It is possible for plants to reach 10′ feet tall and wide, but quite unusual.
Flowering & Fragrance
The plant produces beautiful pom-poms of white flower color throughout the summer into early fall. Expect blossoms from early summer – June through September.
The sweetly scented flowers are showy, impressive and attractive to pollinators.
Troubles with your Hydragenas not flowering?
The stems are grayish-green, and the leaves oval, sharply toothed, dark green on top and light green on the underside.
Leaves range in size from 2″ to 6″ inches long. In the autumn, the leaves change color and fall from the plant.
Light & Temperature
Wild hydrangea grows easily in a partial shade setting with well-drained moist soil.
The spreading hydrangea can also grow in full sun if you provide plenty of water.
In areas with very harsh winters, the plant may die back to the ground, but this is not a cause for concern.
The wild hydrangea blooms on new wood. Plants that died back to the ground or pruned to the ground in advance of winter will easily flower when bloom time arrives.
This hardy native plant grows well in a wide variety of USDA hardiness zones 3 – 9.
Avoid extremes of heat or shade because these will stunt the plant’s growth and limit its flower production.
Watering & Feeding
These plants like moderate soil moisture but cannot tolerate standing in water for long periods.
Although the plant is highly adaptable, it is not drought tolerant. When the weather is very dry, the foliage tends to drop.
Do not allow the soil to dry out thoroughly between waterings. Keep the soil evenly moist.
If your hydrangea is not getting enough water, the leaves will yellow unseasonably and fall.
This is a sure sign you need to give the plant a drink.
Before planting the smooth hydrangea in the ground, be sure to aerate the soil so the roots will have an easy time to become established.
Water generously at the time of planting, but don’t fertilize.
This encourages the roots to develop faster as they seek nutrients.
If planted in soil amended well with organic matter, plants should not need fertilizer during its first year.
In the second year mulch around the plant with aged cow manure.
Be careful not to allow the manure to touch the stem of the plant is it may burn it.
Fertilize with cow manure either early spring or late winter.
Soil & Transplanting
This highly adaptable plant does well in a wide variety of soils ranging from dry to wet to clay to shallow.
Even so, because these plants are woodland plants, they do best in very rich, loose, mineral filled soil.
For best performance provide well-draining, loose soil richly amended with organic matter. Try for a neutral to slightly acidic pH value.
Grooming & Maintenance
Maintenance requirements are quite low.
If the plant grows tall and with flower heads of heavy blossoms, stake it or place a tomato cage around it to prevent the plant from falling over.
Because these plants grow tall and the flowers can be heavy, it’s a good idea to select a sheltered location to protect them from the wind, which can cause the stems to break.
Cutting the plant back to the ground at the end of the growing season is optional.
If you do not prune your hydrangeas back in advance of winter, you should remove damaged, weakened stems in the early springtime.
NOTE: The most popular cultivar is Hydrangea arborescens ‘Annabelle’ – Considered deer resistant, very large rounded white snowball flowers in June and July.
How To Propagate Hydrangea Arborescens
This plant does produce seed pods, but the sterile flowers produce no viable seeds.
Although hydrangeas will grow from cuttings, layering is the best and easiest method.
The Layering Process
- Begin layering early in the growing season.
- Choose a flexible shoot growing low to the ground on the parent plant.
- Dig a small trench in the ground beside the parent and carefully bend the shoot into the trench.
- Cover it with soil and place a rock or a brick on top of it to hold it into the soil.
- The end of the shoot should be protruding from the soil.
- Continue to care for the parent, making sure the shoot you are propagating gets regular watering.
- When you see that the layer has begun to produce new growth of its own, you will know it has set some roots in the soil.
- You can now cut the stem to separate it from the parent plant.
- Leave it in place until it really begins to flourish and then transplant it to its new location or pot.
Hydrangea Arborescens Main Pest or Disease Problems
Hydrangea of all sorts are highly susceptible to problems caused by dampness. Among them are:
- Powdery Mildew
- Mold and Rust
- Bacterial Wilt
- Bud Blight
- Leaf Spot
Provide plenty of space between plants to allow for good air circulation and avoid problems with fungal related infections.
Pests which might plague this plant include:
To avoid these problems, start fresh every year by pruning the plant all the way back to the ground before winter.
Is Seven Bark Plants Considered Toxic or Poisonous?
The sap of all hydrangeas contains glycoside which is an allergen for some people.
It’s a good idea to wear gloves when handling and pruning hydrangeas.
Wash up well afterward. Additionally, hydrangeas are toxic, so keep kids and pets away.
Is Wild Hydrangea Considered invasive?
This native plant is not considered invasive in the United States.
Suggested Hydrangea Arborescens Uses
This plant does well naturalized in a woodland setting, where it resists rabbits attacking.
As a woodland plant, Hydrangea arborescens does well planted as an understory below trees, and grows happily around Black walnut trees.
It is also a good addition to a rain garden and used effectively on a hillside landscape with slanting soil banks to resist erosion.
Wild hydrangea does well planted in a group or as a specimen plant.
It’s a nice addition to a mixed shrub border or a perennial border.
It does well planted in rows alongside a house or wall where it can get sun part of the day and part shade during the day.
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