Incredible Smooth Stem Hydrangea: June 2024 Plant of the Month

As the summer sun begins to warm Midwestern gardens, the Smooth Stem Hydrangea, Hydrangea arborescens, steps into the spotlight as the June Plant of the Month for the Chicago area. Known for its lush, dome-shaped clusters of delicate white flowers, this native beauty not only enhances garden aesthetics but also offers remarkable adaptability to the local climate. Here, we delve into why the Smooth Stem Hydrangea has earned this accolade, alongside planting recommendations, maintenance advice, and recommended cultivars to help Chicago gardeners make the most of this exquisite plant. 

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Why Hydrangea Arborescens?

  • Native Resilience: One of the standout qualities of the Smooth Stem Hydrangea is its native status. Being indigenous to the eastern United States, it thrives in the Chicago region’s climate and soil conditions, offering a low-maintenance yet visually stunning option for gardeners. 
  • Extended Bloom Time: Starting in June, Hydrangea arborescens begins its flowering season, which often extends into the summer. Its prolonged bloom period makes it a star attraction in gardens, providing continuous beauty and interest. 
  • Versatility and Hardiness: This hydrangea species is exceptionally hardy, tolerating USDA zones 3 to 9, which comfortably includes Chicago's zone 5. It handles the city’s hot summers and cold winters with aplomb, making it a reliable perennial choice. 
  • Wildlife Friendly: The Smooth Stem Hydrangea attracts pollinators like bees and butterflies, contributing to the ecological health of urban and suburban gardens. Its dense foliage also offers shelter for various small creatures, supporting local biodiversity.

Recommended Cultivars


Perhaps the most well-known cultivar, 'Annabelle' is prized for its large, rounded clusters of white flowers that can reach up to 12 inches in diameter. It is incredibly hardy and can thrive in both full sun and partial shade. Shop


This cultivar is known for its enormous blooms that are even sturdier than those of 'Annabelle'. 'Incrediball' flowers start out a lime green, turning to white and then back to green as they age, providing a dynamic display. Shop.

Invincibelle Spirit II’

A pink-flowered variety, 'Invincibelle Spirit II' offers a splash of color and supports breast cancer research, with a portion of sales being donated to fund research initiatives. The blooms are strong and reblooming, ensuring continuous color. Shop.

Planting Recommendations

  • Site Selection: Choose a location that receives morning sun and afternoon shade. While Hydrangea arborescens can tolerate full sun, partial shade helps protect it from the intense midday heat, ensuring optimal growth and flowering. 
  • Soil Preparation: Hydrangeas prefer well-drained, loamy soil rich in organic matter. Amend garden soil with compost or well-rotted manure to enhance fertility and drainage. This preparation ensures robust root development and healthier plants. 
  • Planting Time: Spring or early fall are the best times to plant Hydrangea arborescens. These periods provide moderate temperatures and ample moisture, allowing the plant to establish itself before facing extreme weather.

Planting Process:

  1. Dig a hole twice as wide and as deep as the root ball.
  2. Place the plant in the hole so that the top of the root ball is level with the soil surface. 
  3. Backfill with soil, firming it gently around the roots. 
  4. Water thoroughly to settle the soil and eliminate air pockets.

Maintenance Tips

  • Watering: Keep the soil consistently moist, especially during dry spells. A deep watering once a week is typically sufficient, but adjust frequency based on weather conditions. Mulching around the base helps retain soil moisture and regulate temperature. 
  • Fertilizing: Feed your Hydrangea arborescens in early spring with a balanced, slow-release fertilizer. Avoid excessive fertilization, which can lead to lush foliage at the expense of blooms. 
  • Pruning: Prune in late winter or early spring before new growth begins. Remove dead or damaged wood, and thin out crowded stems to improve air circulation and sunlight penetration. For a more compact shape, cut stems back to the ground. 
  • Pest and Disease Control: While generally resistant to pests and diseases, monitor for common issues such as aphids, spider mites, and powdery mildew. Treat infestations with insecticidal soap or horticultural oil, and ensure proper spacing and airflow to prevent fungal diseases.

The Smooth Stem Hydrangea, Hydrangea arborescens, stands out as a stellar choice for Chicago gardens in June. Its native resilience, extended bloom time, ease of care, and diverse cultivars make it a valuable addition to any garden. By following proper planting and maintenance guidelines, gardeners can enjoy the serene beauty and ecological benefits of this hydrangea throughout the summer months. As you plan your garden this June, consider welcoming the Smooth Stem Hydrangea into your landscape for a touch of natural elegance and enduring charm.

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Jennifer Brennan

Chalet Horticulturist