Hydrangeas in Southwest Idaho: Finding the Right Fit

While some may believe that hydrangeas are difficult to grow in the Treasure Valley of Southwest Idaho, the truth is that with careful selection and proper care, these beautiful blooms can thrive here. The key lies in understanding the different types of hydrangeas and choosing varieties that are well-suited to our climate.

Southwest Idaho generally falls within USDA hardiness zones 6 and 7, characterized by hot, dry summers and cold winters. This means that not all hydrangea varieties will flourish here. The most reliable options for our region are typically those that bloom on new wood, meaning they form their flower buds in the current growing season. This is advantageous because even if winter damage occurs, the plant will still be able to produce flowers.  

Here are some popular and successful hydrangea types for Southwest Idaho:

Panicle Hydrangeas (Hydrangea paniculata): These are arguably the most adaptable and heat-tolerant hydrangeas for our area. They can handle more sun than other types and offer a long bloom period, often starting in mid-summer and extending into fall. The flower heads are typically cone-shaped and come in various shades of white, cream, pink, and even burgundy as they age.  

• Popular Panicle Varieties: 'Limelight', 'Little Lime', 'Pinky Winky', 'Quick Fire', 'Vanilla Strawberry', and 'Bobo'. 1  

  

  This is a standard Quick Fire Hydragea tree. Image from https://www.fast-growing-trees.com/

Smooth Hydrangeas (Hydrangea arborescens): Known for their large, round, snowball-like white blooms, smooth hydrangeas are another excellent choice for Southwest Idaho. They prefer some shade, especially during the hottest part of the day.  

• Popular Smooth Varieties: 'Annabelle' and 'Incrediball'.  

  

  This is the INVINCIBELLE SPIRIT® II SMOOTH HYDRANGEA found on at Great Gardens

While Bigleaf Hydrangeas (Hydrangea macrophylla), with their classic blue, pink, or purple mophead and lacecap flowers, are highly desired, they can be more challenging in our climate. They typically bloom on old wood, making them susceptible to bud damage from winter cold. Some newer reblooming varieties that flower on both old and new wood offer more hope, but still benefit from some winter protection. Additionally, our alkaline soils tend to push their blooms towards pink.

• Potentially Suitable Bigleaf Varieties (with extra care): 'Endless Summer' series, 'BloomStruck', and 'Twist-n-Shout'.

  

  Found on the Home Depot website

Oakleaf Hydrangeas (Hydrangea quercifolia) are another option, offering unique oak-shaped leaves and cone-shaped white flowers that mature to pink and eventually brown. They provide beautiful fall color as well.  

• Popular Oakleaf Varieties: 'Gatsby Moon' and 'Snowflake'.

Key Considerations for Growing Hydrangeas in Southwest Idaho:

• Sunlight: While panicle hydrangeas tolerate full sun, most other types appreciate some afternoon shade to protect them from the intense summer heat.

• Soil: Hydrangeas generally prefer well-draining soil. Amending heavy clay soils with compost can improve drainage. For bigleaf hydrangeas, soil pH will affect bloom color (acidic for blue, alkaline for pink).  

• Watering: Consistent moisture is crucial, especially during hot and dry periods. A drip system can be very beneficial.  

• Winter Protection: For bigleaf and potentially oakleaf hydrangeas, providing some winter protection, such as wrapping the plant or mulching heavily, can help protect the flower buds.  

• Pruning: Pruning needs vary depending on the hydrangea type. For new wood bloomers (panicle and smooth), prune in late winter or early spring. For old wood bloomers (most bigleaf and oakleaf), prune immediately after flowering in late summer. Reblooming bigleaf hydrangeas require minimal pruning.  

By selecting the right hydrangea varieties for Southwest Idaho's climate and providing them with appropriate care, you can enjoy their stunning blooms in your garden. Consulting with local nurseries is also highly recommended, as they can offer valuable insights specific to our region and suggest varieties that thrive locally.