Hydrangea arborescens, also known as smooth hydrangea, is a flowering shrub native to the USA. These low-maintenance plants grow naturally around moist streambanks or sloping hills. Most cultivars of Hydrangea arborescens have large white flowers, but some newer varieties have pink blooms. These shrubs are easy to grow, drought-tolerant, and naturally pest-resistant.
Hydrangea arborescens basics
Hydrangea arborescens is a species of hydrangea native to the eastern USA. This flowering deciduous shrub grows in the moist soil below deciduous trees, often alongside riverbanks where moisture is readily available. Hydrangea arborescens natural range extends from southern New York down to Florida, and over to Oklahoma and Kansas.
There are quite a few different cultivars of Hydrangea arborescens to choose from. The most popular variety of Hydrangea arborescens is the ‘Annabelle’ hydrangea. The ‘Incrediball’ Hydrangea arborescens is also very popular, as is the ‘Invincibelle’ series. Most Hydrangea arborescens cultivars have white flowers, but there are a few varieties with pink flowers (like ‘Invincibelle Blush’).
Growing Hydrangea arborescens
Hydrangea arborescens are also called smooth hydrangea, wild hydrangea, or sevenbark. While out shopping for plants, you may have noticed it is difficult to find Hydrangea arborescens by name. Plants at nurseries more commonly go by “smooth hydrangea”, “wild hydrangea”, or by the cultivar names (shown in the section above).
Hydrangea arborescens shrubs generally grow about 6′ (2m) tall but can reach up to 10′ (3m) tall. The Invincibelle series is generally shorter/smaller. Colonies of shrubs form as the stems at the soil surface spread horizontally and grow new buds. The flowers grow in large puffball-like flowers, generally white or cream in color. Blooming generally starts in late May and continues through July. The flowers can be left on the plant in the form of dried flower heads to provide off-season interest.
Hydrangea arborescens are particularly popular because of their rapid growth towards maturity and large blooming flowers within the leaves. These plants can reach a mature size of 60 inches in height and width, which makes them a great centerpiece or space filler in a yard. These plants are also great for borders in yards because of their natural but stunning appearance. The flowers typically do not have a strong scent from far away but are delightful when smelled close up.
These hydrangeas bloom during early summer and begin to grow stunning white and cream flowers. Bright green leaves will also begin to appear in late spring or early summer. As the season goes by, the flowers will begin to droop and fall, and the leaves will turn yellow and eventually fall as well. Hydrangea arborescens are perennials, which means they will return bigger and stronger each year. This continues until the plant reaches full growth. Hydrangea arborescens reach their full height and width (60 inches!) after only 2-3 years if properly cared for.
How to plant Hydrangea arborescens
Planting Hydrangea arborescens shrubs is quite simple, although it is easiest when done at certain times of the year (and often more successful).
When to plant Hydrangea arborescens
The best time to plant a Hydrangea arborescens shrub is early spring or fall. Avoid planting Hydrangea arborescens during the hottest part of the summer, as it will be hard for the young plant to stand the summer heat and sun, even with proper watering.
Where to plant Hydrangea arborescens
Choosing the correct location for your hydrangea arborescens is critical to ensuring the growth and development of your hydrangea arborescens. Choosing the correct location can be the difference between a large thriving bush with vibrant blossoms and a struggling bush that produces only a few scrawny blooms.
The flowers on hydrangea arborescens are in full bloom during the early morning or afternoon shade of sunlight. Planting your hydrangeas in an area where they will be able to receive lots of sunlight but also have some afternoon sun (partial to full sun) is the best place for them. The further north, the more sun hydrangeas require. Keep this in mind when finding the right spot for your new yard addition.
When choosing the location for hydrangea arborescens, you also want to make sure that they will have enough room to grow and reach full development without pruning. It is good to keep in mind that these plants will reach a height and width of 60 inches (5 feet). If you want to have a plant this tall or wide, ensure you have given it plenty of room to develop.
Another factor to keep in mind is the surrounding plants. If you are planting your hydrangea arborescens under or near a growing tree, this will be fine for a season or two, but once the tree begins to fully develop, the hydrangea arborescens will no longer receive all the sunlight it needs to properly grow and mature. Also, the roots of trees are very invasive and will likely take all the moisture from the hydrangea arborescens. For a plant that requires a lot of water, it is not a good idea to plant it near a tree that is selfish with the moisture in the soil.
The best planting soil for Hydrangea arborescens
When planting Hydrangea arborescens, you should begin by ensuring the soil in the area is somewhat nutrient-rich. Hydrangeas can, of course, be fertilized to make up for poor soil, but they should be planted in fertile soil if possible.
Along with properly nutrient-rich soil, you also need to ensure the place you choose to plant and grow your hydrangea arborescens is an area that has proper drainage. If there is no proper drainage in the soil, the roots of your hydrangea could rot and destroy the entire plant. Also, check that water will be available for the plant. Hydrangeas love water and cannot survive without it. There is a fine line you must follow with hydrangeas, but once found, these plants will thrive and grow.
When planting your new shrub, ensure you are not planting it deeper in the soil than it was planted in the pot. The same amount of the plant should be in the soil as was in the pot. This is a great rule of thumb when unsure how deep to plant your new plant.
How to care for Hydrangea arborescens in the garden
Hydrangea arborescens plants are fairly low-maintenance. These USA-native plants are well-adapted to growing in the home landscape.
Fertilizer for Hydrangea arborescens shrubs
Hydrangea arborescens are generally fed in the early spring and sometimes in mid-summer. Different fertilizer products have different guidelines for how much and how often to apply the fertilizer to the soil around the plant.
As with most plants, you will need to be careful as to how much and how often you fertilize your Hydrangea arborescens. Too little fertilizer combined with naturally poor soil means your plants will develop paleness in their leaves and poor, slow growth.
When caring for these plants, ensure they are receiving the proper amount of water to survive the summer heat. Especially during long spans of dry weather, you will have to water the plants yourself to ensure their growth and life. During the mid-summer months when their water intake will be the highest and it is most critical to water them daily (sometimes twice a day).
These plants often love the sun and are either full-sun or partial-sun, depending on the variety you choose. Ensure that these plants get enough sun to properly grow and mature to their fullest potential, but keep a careful eye on them to ensure they are not getting too much sun. If the leaves begin to droop, this is a sign they are not receiving enough water to make up for the summer sun. As previously mentioned under “Water”, during the mid-summer months when the sun is out the longest and the hottest, this is the time they will need more water to make up for the sun.